Monday, November 25, 2013

Project: Mult-Valve: The Universal Pentode Amplifier


Introduction:
It seems like a long time ago, but I remember when the first Sound Practices magazine came out.  For many American audio nuts, the idea of a using an ancient triode like the 300B in single-ended mode was a new revelation.  Of course this was merely revisiting an old technology, spruced up with some modern twists and a hearty dollop of audio hipsterism.  I easily fell into this new movement, making my first ever piece of DIY gear, a 71A linestage using dual-mono mil-spec potted transformers, gas tube regulation, and some vintage oil caps on the output.  After that, it was a series of amplifiers, including PP 6B4Gs and single-ended 2A3s.  All this on a college student budget.  Once I had a real job, I built was my first 300B amplifier using Thorsten Loech's SV83 pentode driver.

But after a while, my interest in this triode movement began to wane.  It was a problem of speakers:  Low power amplifiers require efficient drivers and my experience with the lower priced offerings, including vintage coaxes and more modern designs, left me unfulfilled.  My first experience with audiophile gear included the wonderful Quad ESL-63 electrostat speakers, and nothing I bought seemed to meet that detail, speed, and snap that I remembered so fondly.  I did, however, found myself willing to compromise, thoroughly enjoying the UREI 813A loudspeaker, which ideally requires more power than I could get out of a common single-ended triode running at sane voltages.

With the UREIs, the best all-around amplifier I've heard to date are the Eico HF-60s.  It's a classic 1950s ultralinear design, but runs the EL34s in heavy Class A.  There is a dynamic ease and sense of unlimited power with these classic 60W monoblocks.  Of course some modern components, the addition of a choke in the power supply, and a "battery bias" mod on the EF86 really brought these ancient wonders up to a new level.  But a close runner up was the 1625 amplifier I built, another Class A wunderkind that sounds much better than one would expect considering the budget build cost.  I began to wonder if I could make an amplifier that would make enough power to drive the UREIs, provide class A output, and have the ability to roll in multiple types of output tubes.  The concept of Multi-Valve was born!




The Design:
Most single-ended amplifiers use Cathode or self-bias.  This is an easy way for the circuit determine the idling current of an output tube.  But since I wanted to roll in different sorts of valves, I decided to go with fixed bias.  This decision complicated the power supply since an adjustable negative voltage is need to put across the grid of the output tube.  This also changes the requirements of the driver tube since output tubes using fixed bias need a smaller grid leak resistor.  That meant my favorite pentode driver was out of the question.  Instead I went with the 5687 dual triode which is a low mu tube that would work well cascaded.



For the power supply, I was limited by the small size of the chassis I had in mind.  So I went with a a simple CLC filter using a 5AR4 rectifier, a Solen, a Triad Choke, and then a larger motor run polypropolene capacitor.  RC filtering with some nice Panasonic capacitors and wirewound resistors provide the lower voltage for the driver stage.  Filament is all AC, but I referenced it to ground using a pair of 100 ohm resistors.  The bias supply is a standard Dynaco-type half-wave solid-state rectifier and some CRC filtering.  A pair of linear potentiometers provided the necessary adjustment, while current meters let me dial in the current of the output tube.  With Pentode amplifiers, a reduction in distortion can be found by the use of a regulated screen power supply.  To meet this requirement, I went with a pair of VR tubes connected in series.


Parts:
Instead of Edcor output transformers with their single output tap, I went with potted James 6123HS, which have the outputs for 4, 8, and 16 ohm speakers.  They also look really nice.  However, for the power transformer, I went with Edcor, but bought plain steel bell covers to match the rest of the metallic look I was going for.  Except for the octal sockets, all the small tube sockets are NOS.  A motor run cap suitable for 500VDC was selected, along with some small current meters, miniature pots for the bias control, and some Tocos volume controls.

The most difficult part of building a tube amplifier is the metalwork and chassis.  Instead of the common wood sides, I wanted something different.  Searching through Ebay, I managed to find a nice Chinese unit that included a bottom and top plate, holes drilled in the back for speaker binding posts, an IEC connector, and a pair of RCA jacks.  It's about the size of a Dynaco 70, but with the size of the output and power transformers, I knew it was going to be a tight fit.  To make the top panel, I did a lot of measuring and made several different versions using the Front Panel Express software.


Testing:
Once I had everything wired up - and it was a tight fit getting everyting inside that small chassis - it was time for some testing.  I first tested the bias controls, making sure that the maximum voltage was set.  I then plugged in all the tubes - GE 5687s, Sovtek 5881WXTs, a GE OA2, and a GE OB2 - except for the Shuguang 5AR4.  Leaving the rectifier tube out allowed me to check that I hadn't messed up on the filament wiring.  Once that checked out okay, it was time for the smoke test.  After I plugged in a pair of cheap test speakers and a running CD player, I had the DMM ready to go with the ground lead already attached to a ground point.

Is there anything more exciting than turning on a brand new tube amplifier?  Okay, don't bother to answer that question - of course there is!  But I still get a little rush even though I've been at this still hobby for 24 years now.  To my surprise there was no smoke or flames shooting out the top.  Instead there was a nice purple glow of VR tubes and that warm orange filament color.  After some quick voltage measurements, I adjusted the bias upward and music started flowing out of the little 4" woofer of the Pioneer test speakers.  Ah, it sounds like magic.


Listening:
After some further measurements and some very minor fixes, it was time for some listening.  The Eico HF-60s were unplugged and disconnected from the system.  Up went the Multi-Valve amp and on went the Cardas wiring.  I replaced the Sovtek 5881s with a pair of vintage Tungsol 6550s which required a bias change.  I started with a Schiller CD on the Sony player, adjusting the gain knobs until I found a suitable match with the Quicksilver preamplifier.  After I was happy with that, it was time to spin some vinyl.  I started with some Tom Waits, checked out some Willie Nelson, and ended up with some Police.  Initial impressions was an amplifier that sounded a little lean, but had plenty of detail, very good bass control, and a suprising amount of dynamics for such a relatively low-powered amplifier.  There was a real 3-D sound with the vocals projected in front of the speakers.  A good beginning...

Of course this amplifier was still incredibly fresh.  Except for the tubes, all the parts were brand new.  So over the course of the next few nights, I used this amplifier to provide background music as I worked out, played video games, or started to brew another batch of beer.  As the hours went on, the lean sound began to recede and was instead replaced by something quite neutral.  I also tried different pair of output tubes that I had lying around - Mullard and Shuguang EL34s.  Both provided very pleasing results, but the vintage Tungsol 6550s seemed to sound the best.


No More Games!
Now it was time for some serious listening.  For this, I invited my fellow local audiophile friend over.  He has a great stash of quality records and also had some different vintage output tubes to try out.  I also replaced the rectifier with a 5AR4 made by Mullard.  Here are some notes from this session:

The first pair of output tubes was a pair of vintage Mullard XF2 EL34s.  Listening to Neil Young - Live at Massey Hall, the darkness and classic warmth of this venerable pentode was obvious.  There was a slight loss of detail, but the overall effect was quite musical.  Some of the macro dynamics seemed a touch restrained.

Next up was the Tungsol 6550.  This pair was from the early 1960s with the grey plates with three holes.  Dynamics really improved here with tight and well-defined bass.  There was also a sense of ease to the music, making the amplifier sound much more powerful than the estimated 15Ws.  Treble detail and extension wasn't the best I've ever heard, but it was still very good, but perhaps lacking that last bit of shimmer and liveliness.  Robert Ludwig's mastering of The Band - s/t album was the best I've ever heard it, managing to find clarity in this darkly recorded album.  On the other hand, Donald Fagan - The Nightfly still had speed and the latent fingerprint of a digital recording.

For the next record, a pair of 1950s Dutch Philips EL34s was selected.  These metal base tubes are quite expensive these days, but there was some real magic here.  Listening to Cat Power - Jukebox was an amazing experience, pulling me into the music in a way that made it seem real and alive; as if I were sitting thirty or forty feet away from the band in a small hall.  There was an evenness to the music from the top to the bottom without any  part of the frequency spectrum sticking out in an unnatural way.  Dimensionality and soundstaging was some of the best I've ever heard.  Even more surprising was the controlled but taut bass through the 15" Eminence woofer.  Very impressive.  These tubes appear to be made for this amplifier.

The following experiment was not much of a success.  A fresh pair of early 1950s Tungsol 6AR6s was selected, along with an octal socket adapter.  The sound on Steely Dan - Greatest Hits and The Who - Tommy, became very uninvolving and flat.  Perhaps some more break-in time was needed or a different bias point.  It was time to move on and try something different.

1970s Gold Lion KT77s (with black bases):  These sounded much like the Tungsol 6550s with excellent bass control and incredible dynamic range.  It was, however, a little richer, hewing somewhere between the dynamic Tungsol 6550 sound and the classic richness of the EL34.  Neil Young - Tonight's The Night delivered all the tortured darkness that I expected with a sense of realism that was inviting.

For a more budget choice, I also tried a pair of SED 6L6GCs, one of my favorite modern production tubes.  Though there was a slight loss of the last bit of detail, the overall sound was very pleasant with only some slight overlaid grain over the music.  The explosive dynamics on Blue Nile - A Walk Across the Rooftops were really a surprise, while the Police - Synchronicity kept the rhythm and pace of the music together in a bouncy and engaging way.


The Scorecard:
Bass: Normally a weakness of tube amps, and even more so for single-ended, the Multi-Valve was a real surprise here.  The lowest notes were deep, well-damped, and had excellent control without the slight tubbiness I normally associate with tube amplifiers.  This is a testament to the James output transformer and the feedback loop controlling the woofer.  Not only was there depth, but detail, whether it was the smack of a tom-tom, or the playfulness of a skilled bass player.

Midrange: Clear, defined, and transparent are the first words that come to mind.  The music is served in an even-handed fashion without tube bloat or an overly analytical presentation.  The quality here is quite dependent on the output tube used, ranging on the scale from amazing (Tungsol 6550s and Philips EL34s) to a more middling sound (Mullard EL34s or SED 6L6GCs).  But at no time, except for the 6AR6s, was I actively disappointed by the music coming out of the speakers.

Treble: This again was dependent on the output tube selected for use, with varying levels of quality.  I preferred the Philips EL34s and the Gold Lion KT77s here, while some listeners, depending on the speakers used, may prefer the warmth of the Mullard XF2 or the qualities of the Tungsol 6550s.  At its best, the Multi-Valve amplifier treble is perfectly integrated into the midrange, not calling attention to itself, but not lacking in detail or extension.

Soundstaging: Whoah!  Images are way beyond the edges of the speaker, making my listening space sound larger than it is.  There is also an incredible amount of depth.  Vocals are also projected forward in a nice fashion, keeping separate from the rest of the music.  This clarity comes from the lack of sonic mud, allowing the listener to "see" deep into the musical performance.

Intangibles: Considering the limited power that single-ended can deliver, one of the biggest revelations was the handling of macrodynamics.  Even at lively listening levels the amplifier never failed to deliver the wattage when needed.  This, along with the various microdetails and instrument shadings, gave a unique presentation that makes so many other tube and solid-state amplifiers sound cloudy or unfocused.  The Multi-Valve isn't stubbornly analytical either, bleaching out warmth or lacking humanity.  Instead the presentation is incredibly balanced.  An amplifier like this would be a great tool for mastering or component evaluation.


Conclusion:
There really is something special about single-ended designs, whether they are triode, ultralinear, pentode, or even solid-state.  It's the Class A power that really matters in the end, along with the uncomplicated driver circuits and simplified power-supply requirements.  A pentode, at least with regulated screens and negative feedback, gives a different presentation than, for example, the classic WE91 300B design.  Of course listening preferences, speaker selection, and source components will greatly effect the best amplifier to use in a given system, but with mine, the Multi-Valve is perhaps the best I've ever heard.  Really.  It's also great fun to sample different output tubes and the unexpected differences between them.  Highly recommended.

Parts list and Front Panel Express layout available upon request.


Review System:

VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Amperex 12AU7
Cardas Quadlink 5C 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s & 5AR4s, GEC CV4085s, and GE 6SN7GTAs.
Cardas Hexlink speaker cable
UREI 813A monitor speakers
VTI BL503 equipment rack

Wednesday, September 18, 2013

Refurbishing a vintage Sony TA-3120A solid-state amplifier



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The original Sony TA-3120 is quite the ancient (solid-state-wise) piece of gear.  As far as I can tell, the original TA-3120 amplifier was released in 1966, the start of the decline of vacuum tube technology.   It was this model, along with many others, that was also the beginning of the end for American stereo manufacturers.  Thanks to truly portable radios, the Japanese had a leg up on making solid-state gear that didn't blow up and could provide countless hours of trouble-free operation.

(right click to see larger image - or check out the service manual)
Note: this is the 3120 schematic, the 3120A appears to be slightly different.

The TA-3120 and the latter TA-3120A features very simple circuitry, looking quite valve-like in operation.  A quick look at the schematic reveals a very simple single voltage power supply, a single transistor gain / and single transistor phase-splitter, two pairs of output transistors per channel, and a large capacitor coupling the transistors to the speaker.  My own interest in these types of amplifiers are purely historical.  Though I believe a good tube or a modern circuit will lay waste to these early units, I also have an interest on hearing just how good these things could potentially sound.  Those vintage electrolytic capacitors, especially back then, weren't particularly well-made, not compared to the tightly wound models of today.

These stand-alone "one third" amplifiers seemed to have been rarely used with a preamplifier - instead they were supposed to be mated with integrateds, powering the back channel in early Quad / primitive surround sound systems.  Making a decent - for the time - 50 watts per channel this amplifier will have enough moxy to drive most speakers, provided the they don't dip below 4-ohms impedance.  The capacitor coupling will also save woofers if the output transistors decided to go south.  I also like adjustable gain knobs in back, perfect for matching up with any number of different preamplifiers.  With that in mind, along with the handsome chrome shoebox looks and potted power transformer, I decided to buy one for a paltry $129 and see how it sounded.

  

Initial listening results through the UREI 813A speakers were unfortunately short-lived.  However, before the problem came to light, I heard an amplifier that sounded pretty good but a tad "confused" with not very good control over imaging and soundstage placement.  There was a "blur" to the sound, along with a recessed midrange and a slightly tizzy treble.  Bass response was half-decent though definitely not approaching the uber-depth and control of my old Threshold S/500 or even my Eico HF-60 tube amplifiers.  But still, I would rate these higher than stock Dynaco ST-80/120s or even many vintage receivers I've heard.  I could tell the fine fellows at Sony had put some serious thought into these amplifiers but were hampered by the technology of the time.


A few minutes of listening and the sound suddenly cut off.  And then mysteriously it came back.  Only to be cut off again.  At first I thought some speaker protection relay - as seen in the TA-3120 schematic - was clicking off and on.  However, an examination of the 3120A innards showed no such circuit.  A quick check of the multimeter showed that the power supply was undulating from 62 to 82Vs roughly every two seconds.  As the voltage dropped, so would the sound.  This pointed to a potential capacitor problem - a device that stores and releases voltage.  To the Digikey site I went - it was time to replace every capacitor on the circuit board.  Like the original amplifier, I went with Elna (mostly Silmic) capacitors where possible.  I also discovered that the TA-1320A is quite different than the original 3120, with different values and some there not at all.  So if you need to do this job, record the capacitors needed from the components on the circuit board, not the schematic.


Yikes!  This was a nightmare.  Even though Sony had thoughtfully made it easy to pop off the three circuit boards in question, I still opted to keep the multiple leads intact.  This left me a few inches between the back of the PCB and the heatsink.  The solder traces are also extremely fragile and appear to be made of very thin copper - use caution!  When I was done, I had a nice pile of used capacitors and a much more modern looking board.

 

When I finally finished, I hooked up my Pioneer test speakers and took the output directly from the SACD player.   I turned the amplifier on ... and hurrah!... there was music!  I let it play and tested this power supply voltage.  This time it was a rock steady 86 volts, higher than the initial value.  Since I hadn't replaced the main bucket capacitor which I thought was the source of the original problem (and the most expensive fix) I was happy to hear undistorted sound.  The Pioneer speakers, however, aren't the highest in fidelity, but still good enough for some initial thoughts and component break-in time. 

Hmm... good bass response and a bouncy engaging rhythm.  A very pleasant background sound as I help my fellow marines hammer through the defense of Iwo Jima - courtesy of the virtual world of Rising Storm, a Red Orchestra 2 upgrade pack.  However, the old saw "all amplifiers sound the same" really does hold true, but only if the speakers in question can't resolve the differences.  It was time for a true sonic torture test, the venerable UREI 813A monitors with their compression horn tweeters, a speaker that has broken many an amplifier.

Hooking up the Sony amplifier was easy as pie - the back connectors work great with the mid-sized spades of the Cardas Hexlink speaker wire.  Large spades and banana plugs please do not apply.

The first cut was my original U.S. pressing of Tom Waits - Closing Time.  This recording is a tad dark and it showed.  The upper midrange / lower treble grit I normally associate with solid-state gear was pretty suppressed - you had to really listen for it to hear it.  Only a few non-tubed amplifiers truly get rid of it - at least according to my experience.  The next recording was the 180g re-issue of Ray Charles - Genius + Sould = Jazz.  I was taken aback by the sheer musicality of the sound.  I began to feel a tad suspicious, wondering if I was hearing one of the better amplifiers of my life.  Seriously.  The dynamic swings worked well and the spaciousness of the recording was evident; this sort of depth is something I normally associate with tube amps.  Hmmm....

Next up was a first pressing of Donald Fagan - The Nightfly.  Ah, now I could hear the limitations of this early digital recording.  The treble was noticeably splashy and forward.  The very deepest bass was not exactly missing, but not as low as I remember with other, more powerful amplifiers.  The separation of the vocals were not as defined as other amplifiers caused by a slight blurring and loss of detail.

Now it was time for something really dynamic - The Classic Records re-issue of The Who's - Tommy and my original pressing of Frank Sinatra - Sinatra At the Sands.  With these two recordings, everything was there and the music was still emotional as ever, but the lowest bass registers were just slightly underdamped and lacking - perhaps an effect of the music going through such a large electrolytic output capacitor.  The very top could get hard and uncontrolled when listening too loudly, the sign of an amplifier running out of steam - obviously 50Ws can only do so much.

Conclusions?  This is a very nice amplifier, especially with a bevy of new Elna capacitor replacements.  Perhaps it is the simple circuitry or the effects of the (fairly) non-linear output capacitor, but the Sony TA-3120A lacks much of the grit and harshness I associated with solid-state gear.  Sure I've heard better - notably a large number of tube amplifiers, but if I didn't know any better, I could really live with this piece of vintage amplifier.  What it lacks is the ultimate finesse of the best gear I've heard - detail retrieval, bass control, and soundstage depth.  However, it does - much like the B&K ST-140 but not quite as warm - convey the music in an enjoyable way.  Of course much of this may come from my VPI table and Quicksilver preamplifier; the flaws of the Sony diminished by the strength of the other audio gear.  Nonetheless, recommended for vintage junkies who want to try something different.

Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Amperex 12AU7s
Cardas Quadlink 5C 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s & 5AR4s, GEC CV4085s, and GE 6SN7GTAs.
Cardas Hexlink speaker cable
UREI 813A monitor speakers
VTI BL503 equipment rack

Tuesday, September 10, 2013

New Project: Universal Single-Ended Pentode Amplifier



I've recently built two budget orientated single-ended amplifiers, one using the WWII-era 1625, and the other using the 6CB5A connected as triode.  Both were built to a price point - Edcor output transformers and parts sourced from Mouser.  The sonic results for these unusual designs were quite gratifying, considering the sub-$700 price range.

Sonically, I actually preferred the sound of the 1625 amplifier which was used as a pentode with screen regulation.  It had a pleasant forward sound compared to your average triode, and also seemed to develop much more power than expected, along with greater speaker control with the use of (yikes!) negative feedback.  This project made me rethink an older amplifier I built using the EL156 output tube connected in Ultralinear.  I began to wonder how a true pentode assault on the "state of the art" would sound.

With that in mind, I came up with the following concepts to guide me through the design process:
  • Ability to use octal socket output tubes: 6550, EL34, 6L6GC, KT66, etc
  • Fixed Bias - allowing the maximum range of bias 
  • Plug-in Plate cap: for the weird tubes
  • Pentode operation - possibly with a triode switch
  • Tube rectification using damper diodes
  • Screen regulation using gas tube shunt regulation
Perhaps "state of the art" was the wrong term to use since I won't be spending hundreds of dollars on Teflon coupling caps, but I will be using higher-level James output transformers, Rel-Cap polysterene couplers, and some really nice Nichicon electrolytics.  And I have a pair of vintage TungSol 6550s that are just crying out to be used!  Stay tuned for the schematic, build pictures, and listening results.


Thursday, July 25, 2013

Review: Monoprice MHP-839 headphones

(image from Google)

Having never spent more than a $79 on a pair, I'm a admitted headphone cheapskate.  For work, I'm a longtime user of the budget Sennheiser HD-201, while for home use, the Grado SR60s get the nod.  At heart I will remain a speaker guy since the visceral gut impact of something like the UREI 813As just can't be matched even by the finest headphones.  But for listening to MP3s at my desk or while doing late night mixdowns of my amateur synth music, it's hard to beat the sonic solitude of a pair of headphones.

When I finally decided to give up the Sennheiser HD-201s, a good audiophile friend recommended the Monoprice MHP-839s.  He's a longtime Sennheiser HD-600 user, but commented that the Monoprice headphones were quite enjoyable with a nice overall sound for the price.  I ordered my pair from Amazon - hey, free shipping! - and got them a few days later.

After a few hours of break-in, I found the Monoprice headphones to be quite decent.  The lowest bass goes quite deep with more impact and slam than the old HD-201s.  They also have a richer midrange, making the Sennheisers sound a bit nasal and hollow.  Perhaps the Monoprices are a tad congested - for example, sounding like a doped paper woofer than something like Kevlar.  Their biggest failing is in the treble.  My middle-aged ears don't quite hear the higher frequencies like they used to, but even I could hear a steep roll-off here.  This isn't a big deal for MP3 sources or anything that was recorded a little on the hot side - like many Synth or Dance mixes, but could be a deal breaker for the serious audiophile.  With their open back design, I prefer the Grado SR60s - they have a clarity that is hard to beat for the price - but such a design wouldn't work for my workplace.

As far as design, the Monoprice headphones aren't quite as comfortable as the Sennheisers.  I notice my ears getting hotter quicker.  I have a fairly large noggin though, so perhaps I'm stretching the band pretty hard.  Compared to the HD-201s, the background noise of a busy office is muted more with the Monoprices.  This is good if you require noise suppression like I do - programming takes concentration.

Construction quality is good - these headphones are built with heavy-duty plastic.  The two different lengths of supplied cords are a nice touch.

Friday, May 3, 2013

Review: VPI Aries 1 turntable


Introduction:
I've been having turntable envy for years.  While I soldiered on with my old VPI HW19 Mark III, my good friend had the much better Mark IV version of the same table.  This included a much thicker platter, plinth, and the well-regarded SME309 tonearm.  These tables are fairly rare, only popping up on Audiogon or Ebay every once in awhile.  I thought of upgrading my own table with a better tonearm and slowly piece together the parts to bring it up to Mark IV status.  However, the parts for these old models are getting harder to find, and frankly the dollar amount made me skeptical of that direction.

Obviously VPI - and other manufacturers - are still making turntables, but most of them lacked an option that I thought was of utmost importance: an active suspension.  The original VPI HW19 turntables were suspended designs, using heavy duty springs in the corners to isolate the plinth, tonearm, and platter from the surrounding environment.  This is hardly a new idea - it has been done with countless turntables like the classic AR, Thorens, and Linn.  On the other hand, I've always associated solid plinth (or non-suspended) turntables with the dreck that came out in the 1970s and 1980s - notably the cheaper Japanese turntables that sprouted up everywhere and gave some of the bad vinyl experience that made consumers flee to the digital world.

So where does the Aries 1 fit into all of this?  Though it is non-suspended, it was also VPI's first foray into this type of design.  It was also supposed to be a cheaper alternative to the TNT, their top of the line model.  So basically the Aries sports the TNT's platter but instead of a spring suspension, it uses a solid (and very thick) plinth.  The tonearm is also an upgrade over the normal Scout of Scoutmaster, using the JMW10.5 instead.  For some reason, not many Aries seem to be sold.  The sit in a sort of middle of the road position in the VPI lineup - more expensive than their entry-level models, but still expensive enough that the alternatives: the HRX, The Classics, or the TNTs are almost direct competitors.  That means you don't see too many Aries around, and the 1 seems to be even rarer.

Based on the reviews, Arthur Salvatore's recommendation, and the quality of the platter and bearings, the Aries 1 has always been on my list of possible upgrades.  Though it lacked a true suspension, I thought that perhaps with enough mass loading, even having the "limitations" of a solid plinth could be overcome.  When a conversation with the owner of local record/stereo store brought up the Aries 1, I knew this was one table I had to try and snag.  He was willing to sell it for a lower price than I was seeing on Audiogon, and it would also mean no shipping.  That means a lot when buying something so fragile.

It only took one glance at the beautiful piano black plinth, the super thick 25lb TNT platter, and the well-made JMW tonearm to know that I would be willing to put a sizable dent into my credit card.  So off I went, heading home with a lovely turntable and a bite of debt.

The Design
As mentioned before, the Aries 1 table sports a heavy-duty platter composed of aluminum and acrylic, weighing in at a heft 25pds.  Supposedly - and I have no direct experience with this - this earliest version is superior to the later lighter frosted acrylics platters.  Beneath this is the thick solid plinth made of MDF and painted with a glossy black.  Like the Scout and Scoutmaster, the motor is not bolted to the plinth. Instead it sits inside a carve out with no direct connection to the turntable except for the belt.  The motor chassis itself is very, very heavy and does not move or rock back and forth when turned on.  The tonearm on this particular version is the JMW 10.5i which has Nordost wiring.  It's a unipivot design which essentially has the entire arm resting on a single minute point.  When moving the tonearm over the records, this can lead to some unsettling rocking side-to-side motion.  However after prolonged use, one realizes how sturdy the whole contraption feels.


Initial Impressions:
Since I only had a Denon DL-110 on hand, that was the first cartridge I plugged in.  With some additional headshell weight - an additional metal tab provided with the cartridge - I soon had the tonearm dialed in.  The supplied VPI jig certainly helped, along with my digital pressure gauge.  More details for setup here.  One thing I really liked was the tonearm connection "junction" box that allows interconnects to be plugged directly into the table.  This is certainly better, at least if you enjoy swapping cables around, than dealing with one set of wire that could possibly be too short.

I threw on a copy of Neil Young - Live at Massey Hall (Pallas) which is a high quality recording.  I was struck by the sheer quietness of the Aries turntable.  The normal background rumble and wash that I unconsciously filtered out with my other tables was suddenly gone.  The effect reminds me, oddly enough, of the CD!  However, the Aries is not lacking in detail, nor are subtle musical cues missing.  Instead the separation of motor, the heavy plinth and platter, along with the tonearm has given this turntable a foundation that allows the music to spring from total blackness.  Simply amazing.

Not only is the background incredibly quiet, but the dynamic and bass control also reminds me of the better parts of digital.  For example, listening to The Police - Synchronicity (Japanese) and there was terrific low frequency control and detail that gave a bouncy excitement to the music.  The dynamic sweeps, from softest to loudest, seem almost infinite in scale.  This is not your father's turntable.

Upgrading the Cartridge:
The Denon DL-110 phono cartridge is no slouch and is certainly one helluva a bargain at $139.  Nonetheless, I felt the urge to upgrade.  A better match for the tonearm was the Dynavector 10X5, a cartridge that I had run before with much success.  Thanks to a friend, I was able to procure one with low hours at a price lower than new.  Once again installation was a breeze.

The Dynavector 10X5 brought further refinement to the sound: more detail, deeper bass, a controlled treble, and a large sense of scale.  The sonic attributes already mentioned: black background and dynamic scale were only improved even more so.  After listening to several records and doing some dialing in with cable swaps, speaker positioning, and tonearm adjustments, I came up with following impressions:

Sonic Attributes:
Bass: This is one of the major strong points of this turntable.  It can reach Stygian depths, the likes that are normally the province of the digitial medium.  Along with this extraordinary depth comes control and slam.  This makes rhythmic music gel together in a foot-tapping way, but also adds to the foundation of the performance.  This level of bass performance is simply wonderful. 

Midrange :Like the bass, the keyword here is control.  The lack of muddiness and the washed out effect that lower turntables generate, leads to clarity.  Minute details are more apparent.  The end result is a very refined sound, but not one that is overtly so.  That is to say the turntable serves the music embedded in the vinyl, not the other way around.  This allows the character of the recording to come through with delicacy, aggression, or whatever was intended by the artist.  This bloom and body is something that the digital medium has a hard time with, and lesser turntables can only catch a glimpse of.

Treble: Refined is the first word that comes to mind.  Like the midrange, the lack of fuzziness brings plenty of detail to the table.  A poor recording will sound harsh, while a good recording will bring out the delicate reverb of the hall or the sweeping shimmer of the cymbal.  There is no glossed over warmth here, or masking effects from roll-off.

Other: If I could fault the Aries in any way, it would be the slight mechanical reproduction of the music.  You see the lack of muddiness leads to an extremely open sound that honestly reminds me of digital in many ways.  Now don't get me wrong, this is no Magnavox CD player, but an extremely musical machine that is also ruthlessly revealing.  This lack of uber-analog warmth my turn off some listeners used to a richer euphonic sound.  Personally I prefer gear that speaks to what the recording has to offer, not to give a pleasant coloration.

Conclusion:
The VPI Aries 1 has been a major upgrade.  Not only has this turntable blown away my expectations of solid versus suspended plinths, it has also brought my entire stereo up another notch in fidelity.  It's quite common to get carried away with a new piece of gear, but lengthy listening has proved that the Aries is no flash in the pan.  In the wide world of turntables, I'm sure *better sonics could be found, but expect to pay for it.  Highly recommended.

* I see that the VPI Aries 3 has an asking price of $6000USD.  I'm not sure if this would be a good bargain, so if you are interested in this particular model, be sure to shop used.  An Aries that has been well cared for will be a better deal than many new turntables in the same price range.

Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Raytheon black-plate 5814
Cardas Quadlink 5C .5M interconnects
B&W Bass Equalizer
Cardas Quadlink 5C 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s, EF86s, 5AR4s, and GE 6SN7GTAs.
Cardas Hexlink speaker cable
B&W Matrix 805 mini-monitors
VTI UF29 stands
VTI BL503 equipment rack

Friday, April 26, 2013

Review: B&W Matrix 805 loudspeakers

 Introduction
Bowers and Wilkins have long been audiophile darlings.  I'm no historical expert, but from my many years of reading the audio specialty magazines, it is the venerable 801 studio monitor that cemented their reputation.  Unlike many other speaker makers, they also produce their own drivers, and have an engineering staff on board to build excellent crossovers and cabinets.  This attention to quality is hardly extraordinary in the world of audiophiles, but like their British competitor KEF, it speaks of a long term love of the black arts of speaker design.

My own personal experience with B&W is very, very short.  The only pair I've personally heard was back in the 80s, when my best friend had a pair of stand mounted units of an unknown model.  I don't specifically remember much about the sound other than the speakers could take all the power that the Denon receiver could dish out.  This was, of course, before my audiophile days, when playing clean and loud was all that mattered to my teenage ears.

Time for a New Speaker?
Moving to a new house with a smaller listening space, and a Denon DL-103R cartridge that got damaged during the move, tempered my audiophile equipment craving.  Instead I pulled back on my expenditures, scaling back the size and quality of my system by going with a pair of KEF iQ30 speakers that I already owned, and buying a new Denon DL-110 cartridge.  I even stuck in some Chinese EL34 tubes for my Eico HF60 monoblocks, wanting to save my vintage Mullards for the day when I had a larger listening room.

However, fate being what it is, those plans of hanging back were thwarted by the purchase of a VPI Aries 1.  This was not a turntable purchase that I was planning to make, but it was such a hard deal to pass up - being local and priced lower than what I was seeing on Audiogon - that I took the plunge.  The resulting sound, even through the budget KEF monitors, was a major eye-opener.  I'll be reviewing this turntable in a separate post, but needless to say the overall sound, even with a budget priced Denon DL-110, became much more dynamic, involving, and was quite the step up in reproduction.  After hearing the Aries, I knew that to get the full effect I had to upgrade the rest of my stereo system.  I also knew that with my smaller listening space that approaching the bass and dynamics of the UREI would be near impossible, but perhaps I could be sated with a mini-monitor of high enough quality.

My initial thought was to go with KEF - specifically the KEF LS50, but the low efficiency of 85dB made me wonder if 60Ws of tube power would be enough.  The lower-end models of KEF had their own issues.  For example I wondered if the current Q300 model would really be a major upgrade versus the iQ30s currently in the system.  Browsing through Audiogon for monitors under one thousand dollars, I came across the B&W Matrix 805s, the baby brother of the famed 801s.  My interest piqued, I read the Stereophile review and this post by Ken Rockwell.  Both are excellent starting points if you wish to have a deeper technical description of these speakers.  Needless to say, I was thoroughly interest in this speaker now.  Though the efficiency is only a rated 87dB, it still seemed worth taking the risk.  I purchased the 805s and soon had them in my hands.

Initial Impressions
Opening the box and unwrapping the yards of bubble wrap, I was greeted with a very nicely built pair of mini-monitors.  The enclosure made of rosewood (veneer?) is very lovely.  Binding posts on the rear are recessed and gold.  The woofer is a 6.5" kevlar unit while the removable bullet tweeter on top is a metal dome that is time-aligned by a fourth-order crossover.  An extra feature is the optional outboard electronic crossover/filer the cuts bass off below 10Hz but firms up the response between 10Hz and 50Hz.  This could be useful to reduce turntable subsonics and improve the low-end for rock or symphony music.

Installation was on top of my UTI 29" tall stands, bi-wired with budget Kimber 8PR/4PR.  Distance between the speakers was some 7' from each other and perhaps 2' from the sidewalls and 3' from the rear wall.  Obviously not a cavernous listening area, eh?

Using the Denon DL-110 cartridge, along with Hitachi 5AR4s and Shuguang EL34s installed in the Eico HF60s.  The first record up on the Aries 1 turntable was Neil Young's "Live at Massey Hall".  This recording is fantastic - however with only one singer and guitar (or piano) it is by no means a complex or very dynamic album.  Nonetheless, it is a good album for picking out overall sound quality.  The treble sounded very clean and polite.  The midrange was clear with plenty of detail and space.  The bass, which isn't very deep on this album, had a slightly wooden character.

The next two albums: a German pressing of Pink Floyd's "Animals" and a Japanese pressing of Steely Dan's "Greatest Hits" showed the natural limitations of all small speakers.  As expected, ultimate dynamic range and the lower bass of the B&W 805s were limited by the small woofer size.  Yes, I'm being quite unfair comparing such a minute speaker to the massive UREI 813As, but I'm just reporting what I heard.  When the bass got really deep, the 805s didn't choke, but instead began to slowly compress, leading to the already mentioned wooden character to the bass.  However, throughout the dynamic swings, the sound still remained balanced and focused without getting gritty or uncontrolled like the KEF iQ30s.

Getting Deeper:
Now it was time to upgrade the rest of my system.  First it was a new cartridge: the Dynavector 10X5.  This is a good, dynamic high output moving-coil cartridge that works quite well with the Aries 1 turntable.  After that, it was time to bring out the best tubes I had for my Eico HF-60s.  Out went the Hitachi and Shuguangs, and in went my vintage Mullard tubes.  I also replaced the GEC CV4085s (EF86) with the very earliest and rare "long plate" versions that Mullard made.

These changes were proof positive that rolling in the right tubes can have a major impact on the sound.  Not only did the midrange become more relaxed, but the higher frequencies were even smoother than before.  The Dynavector 10X5 has always been a dynamic cartridge and partnered well with the B&W 805s.  Sure, the UREI 813As still hold sway in the explosive bass department, but for such a small speaker, the overall frequency response was much improved.

You Got to Equalize! 
B&W also included a small bass equalizer with the 805s.  Since I didn't have another pair of Cardas interconnects on hand, I opted to use some budget Canare wire to make the connection between the Quicksilver preamplifier and bass equalizer.  From the output of this little unit, Cardas Cross wire was used.

The change was immediately apparent - this small speaker now growled like a much larger speaker.  Again, it was nothing like a big speaker with multiple drivers, but it sure helped with rock 'n' roll music.  The wooden character of the bass was gone and instead became really firm and punchy.  However there was a bit of detail loss, but for the types of music I listen to, I definitely preferred the improved bass response.  Now I will have to go ahead and buy a short run of Cardas interconnects.  However purists or listeners of lighter fare may prefer the speakers without the additional wiring and active equalization.  Try it both ways.

Speaker Cable Upgrade:
The Kimber 8PR/4PR is great budget wire, but I was curious to hear how my vintage Cardas Hexlink speaker cable would fare.  So back in went the binding post jumpers on the 805s, and on went the Cardas.  The change was quite immediate - the slightly bright, polite sound became much more relaxed.  The top-end treble also smoothed out, turning the monitor into one warm, full-bodied speaker.  Wow.   I would never expect such a major character change from a few feet of cable.

Details R Us
Bass Response:  Hey, this is a small speaker with a relatively tiny woofer.  Expecting subterranean bass suitable for hard rock or organ music is just plain wishful thinking.  If you like that kind of music, you either need a larger speaker or an additional subwoofer.  However, with the B&W bass equalizer installed, lower frequencies are served well enough that I don't miss my big studio monitors (too much).  The sound became really punchy with good detail.  It wasn't all boom either, but instead the bass became very tight and controlled.  Obviously some thinking went into the speaker crossover design and the additional needs of the equalizer.  Again, very dependent on system and musical tastes.

Midrange: Compared to the UREI 813As, which are ruthlessly neutral as befitting a real studio monitor, the 805s have a slightly recessed sound when using the Kimber wire.  This was tremendously reduced by the Cardas cable.  When the music gets really busy or the dynamics really start swinging, it's almost as if the speaker is slightly "holding back" as the big peaks swell up.  Once again, perhaps this is just the effect of a small speaker being asked to do the work of a larger one.

Detail was exemplary - fingers on strings, studio effects, and overdubs were just that more obvious than many other (more budget) speakers I've heard.  The level of available information was much higher than my old Magnepan 1.6QRs, but not quite in the Quad ESL-63 league.

Treble:  The 805 tweeter ranks up there with some of the better I've heard.  It's clean but not totally antiseptic.  It's also very detailed  Sure, it doesn't quite strike in the electrostatic speaker or the plasma tweeter level, but it's no slouch either.  Admittedly there is a slight bump in the highest of frequencies, so some system matching is paramount here.  For example, the wrong solid-state amplification or an aggressive moving-coil or DAC could play havoc with the system balance.  Be also sure to play with speaker wire, as my Kimber vs. Cardas experiment proved.

Other: Even at loud listening levels, the 805s never fall apart.  That is to say the speakers never sound ragged or uncontrolled.  Soundstaging placement, width and depth are also very good, letting instruments and voices sit naturally within the space of the recording.  There was some minor shrinkage - as to be expected - of image size compared to larger speakers.

Conclusion:
Speakers in the less than one-thousand dollar range are a hard nut to crack.  My advice in this range is to buy the best used model you can afford.  The B&W Matrix 805 is one such model.  I'm sure there are many others, but few in this price range can match the engineering, quality, and performance of these top level speakers.  I expect the 805s to have a long shelf-life in my current system.  Highly recommended.

Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Quadlink 5C 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Raytheon black-plate 5814
Cardas Cross 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s, EF86s, 5AR4s, and GE 6SN7GTAs.
Kimber 8PR/4PR 2M bi-wire cable or Cardas Hexlink
VTI UF29 stands
VTI BL503 equipment rack

Thursday, April 11, 2013

Building a single-ended 6CB5A amplifier


Introduction:
After the success and sale of my single-ended 1625 amplifier, for my next amplifier build I decided to return to the venerable triode.  However, I wanted a bit more power than your average single-ended 2A3 amplifier, but still didn't want to use the pricey 300B.  With that in mind, I looked at several push-pull designs using the 6B4G or 2A3.  Once again I ran into expensive tubes, even for Russian or Chinese versions, and pricey interstage iron.  However, after reading several threads on diyaudio.com, I came across Thomas Mayer's blog describing the use of the 6CB5A - a TV vertical deflector tube - in single-ended mode to make 7Ws.  He touted it as a budget alternative to the 300B, and at ~$5 to $6 a pop on Ebay, it certainly would cut down on the output tube cost.


Circuit:
Once I had the signal schematic in hand, I went and designed my own power supply circuit around a Edcor power transformer.  Note that the 6CB5A uses a mighty 2.5As of current at 6.3V.  This required an additional filament transformer for the 6N7 driver tubes, and, in order to reduce costs, I stuck with a 5V rectifier tube since the filament tap was available instead of the recommended TV damper diode which would require an additional transformer..


Parts:
Once again, this is a budget build, so Mouser and Allied Electronics were used heavily.  This means electrolytics used in series to get a high enough voltage rating, Cornell-Dublier metallized polypropolene coupling capacitors, plastic speaker binding posts, and plenty of KOA resistors.  Output transformers are 3.5K/6-ohm units from Edcor.  The power transformer was also sourced from them.  For the top plate I used Front Panel Express.  Wood chassis is from Valab, an Asian Ebay seller.


Construction:
This was an exercise in point-to-point wiring, which can be frustrating if one is not experienced.  A single star ground is used near the RCA input jacks.  Wiring is all plated solid-core.  Due to the simplified power supply and lack of regulation, this unit was much easier to finish than the 1625 amplifier, my last project.


Listening:
After a quick voltage and current check, I hooked this amplifier up to a pair of Pioneer BS-21 speaker that I use for test purposes.  At 84dB efficiency, these aren't exactly a great match for single-ended amplifiers, but at least I can tell if music is being made.  The sound, via my VPI table and Quicksilver preamplifier, was very smooth without any noticeable hum or other noise.  With my medium-output moving coil cartridge, I had to turn the volume control way up to get any decent playback level.  Of course such a low gain amplifier will prove to be useful for much more efficient speakers than the test Pioneers units.

After everything checked out, it was time to listen to the 6CB5A amplifier with the KEF iQ30s.  Once again my big UREI 813As, which would be a much better match, are in storage so I had to make due with what is on hand.

This amplifier is smooth, coherent and almost touches the better 300B amplifiers I have built.  The soundstaging in uncluttered with a deep and immersive soundfield - all traits of a triode amplifier.  The bass was also surprisingly well-controlled, lacking that fat underdamped sound that plagues some tube amplifiers.  Treble extension was smooth with a nice shimmer and swirl to high hats.  Detail was also very good, providing plenty of definition - eg, recordings sounded different and weren't congealed into a "it all sounds the same" blob.

Switching to the less efficient B&W 805s and I noticed the amplifier would run out of steam on big peaks.  Obviously not a good match, but at lower listening levels it was quite the pleasurable listening experience.

Conclusion:
Single-ended amplifiers - even using triodes - require careful speaker matching.  Many speakers are too inefficient and have wild impedance curves that require more power and low output impedances. However, the 6CB5A coupled to the Edcor iron did a decent job driving any of the speakers I have on hand.  Those into rock or heavy orchestra would benefit with more power or horn speakers, so keep that in mind if you're interested in building something like these amplifiers.

Wednesday, April 3, 2013

Dividebytube's Guide to Building an Audiophile System



I've been into this hobby for a number of years and have gone down several dead ends.  This little article is a sort of "lessons learned" piece, which may be of some benefit to a beginner - or even an experienced - audiophile.

Consider the Source:
Like Linn, I believe having a good signal source is the most important part of any good stereo system.  Some others will tell you to spend the majority of the budget on speakers, or even the amplifier.  However, I've found a cheap CD player or turntable will just lead to heartache, making the listener chase their tail trying to find the best speaker or amplifier to match with the inferior sound quality.  Is the speaker too bright or is it the cruddy op-amp in the digital-to-analog converter?  Is the amplifier muddy or does the turntable poorly constructed, picking up vibration?  A fairly neutral source provides the foundation for good system building.

Amplifier Envy:
This idea is closely related to the first concept of source quality - don't go crazy with finding "the right" amplifier until you have nailed down your front end.  Yes, just the right amplifier does make a big difference, especially tubes versus solid-state or Class A versus Class AB, but don't worry about this aspect as much until you have sorted out the source and the speakers.  There are plenty of budget models out there that will do the job until the time is right for an upgrade.

Boom and Sizzle:
Speakers are like luggage - easy to buy and almost impossible to sell.  Before buying any speaker, consider your listening room, environment, and music likes.  For example, a small space will require a small speaker - there is no reason to excite room nodes and get a muddy sound with a monster speaker crammed inside of a tiny space.  If you have little children - a Quad Electrostat or a mini-monitor on a slender stand - may not be the best route.  And small speakers may not reproduce bass all that well, which won't work for head-banging levels, unless a subwoofer is used.

Picking an Amplifier:
I like tube amps, especially single-ended and/or low-powered ones.  Good sounding amplifiers of a higher wattage are few in number, but they do exist.  The Eico HF-60 and (rebuilt correctly) Dynaco Mark III monoblocks come to mind.  However one has to be smart enough to realize that tube amplifiers may not always be the best match for the speaker, especially if low-efficiency, wild impedance curves, or a large listening space is being used.  In this case, perhaps a bigger tube amp or a good solid-state unit is in order.  For example, matching a 20W 6BQ5 amplifier to a pair of Magnepans will lead to nothing but frustration, unless incredibly low playback levels are your thing.

The Good, The Bad, and the Feedback:
Zero Negative Feedback and single-ended was quite the rage for awhile.  However, these types of amplifiers require efficient speakers with higher impedance curves - think Altec-Lansing horns, Klipsch, or (modern) Zu speakers.  Pairing a single-ended 2A3 amplifier to a 4-ohm nominal speaker can result in some strange effects: muddy, underdamped bass or perhaps a rolled-off treble.  Some listeners may like this effect, but it isn't fidelity since the "romantic" tubey sound can dominate the music to the point where the differences between recordings becomes almost negligible.  That is to say, if every record or CD sounds the same, then you're listening to a pleasant distortion machine, not a high-fidelity amplifier.  In this case feedback - if judiciously applied - can actually help, providing speaker damping and extending frequency response.

Short Circuit:
Another strange audiophile fancy is the love for boutique parts.  Now don't get me wrong, I've personally heard differences between coupling capacitors, resistors, and wire.  But I also know that the circuit itself is the most important part, not the parts supporting it.  For example, a poorly design SRPP tube linestage isn't going to be greatly improved by slapping in a Teflon capacitor.  The circuit itself needs to be corrected, or an alternative and improved preamplifier needs to be purchased.

Flash in the Pan:
The high-end audio scene is filled with hyped products and broken dreams.  I could name company after company that have failed since the 1980s, and some of them even produced well-reviewed winners that should have seen these start ups to the road to success.  However, the audiophile market is a niche one and it's apparently quite easy to fail.  Unless you are handy with a soldering iron, my advice when purchasing equipment is to buy from established brands that have been around for awhile.  This will lead to easier service, possible product updates, and better resale value.  Some of the classic brands: Audio Research, Conrad-Johnson, Mark Levinson, KEF, Quad, etc have a long track record and the quality of their gear, plus the resale value shows this.

Vintage Madness:
I love old tube gear and vintage speakers.   However, in the world of amplifiers, only a few of the old designs really stand the test of time.  These were usually the expensive pieces back then  - Marantz, Fishers, the top-level Eicos, Fishers, Dynacos, Grommes, Fairchilds, etc.  On the other hand, the more budget integrated and console amplifiers suffer from poorer circuits, cheaper parts, and output iron with less bandwidth and smaller cores.  The same holds true with speakers - only some have really held up to the test of time, while the majority of the vintage units sound rolled-off and not very detailed.  Sure, these old-timey pieces can sound enjoyable, but they ain't hi-fi.

Separated at Birth:
If you're a simple kind of audiophile who wants the minimal moving parts, then by all means go the integrated or receiver route.  Just keep in mind that this path will minimize - unless in/out RCA jacks are included - your upgrade possibilities.  Personally I prefer separates - preamplifier and amplifiers - which allows different combinations of gear to be tried.  Difficult speakers to drive?  A tube preamplifier and a hefty solid-state amplifier might just be the perfect combination.

Budget Talks:
Even if you are silly rich, every stereo system is built around a budget.  Things to consider: how much are you willing to pay and how will it match with the rest of your system?  I could, with enough bad decisions, put together a fantastically expensive system of Stereophile Class A components that would make any listener run out of the room screaming,  For example, couple a low powered singled-ended amplifier with an inefficient speaker with a low 1-ohm impedance curve.  Though painful, it's best to start with a good front-end, and then buy and sell up the chain, keeping in mind that a manufacturer's lowest priced product is not always the best place to start.  For example it will be better to save to buy a Rega P3 than the entry-level P1.

David and Goliath:
There are giant-killers out there - budget gear that punches above its low price and gives a great listening experience.  KEF and Wharfedale speakers easily come to mind, along with some of the cheaper Chinese tube amplifiers.  However, no matter what you tell yourself, they still are budget pieces that can be surpassed with something more expensive.  It's just a matter of how much you are willing to spend and if you ears really demand that much perfection.  I think it's important not to lie to yourself and accept the limitation of your system, which brings me to my final point.

Times are A-Changing:
When buying gear and bring in a new component into the system, it's all too easy to get swept away thinking that the latest change is always for the better.  It's also far too easy to think an expensive unit will always surpass a cheaper piece.  It would also be wrong to think that newer is always better than older.  Again, system matching and careful listening is required here.  It's also good to have a few audiophile friends over who don't have an emotional investment in your stereo.  If they have experienced ears - and are of an honest nature - they can also tell you what faults they are hearing, instead of just concentrating on the best parts of upgrade.

As always, comments and suggestions are welcome.

Monday, March 25, 2013

Review: Denon DL-110 high-output moving coil

(picture taken from Google Images)

My previous phono cartridge was a Denon DL-103R, the famed 'upgraded' version of the DL-103.  Mine had been modified with an aluminum body.  Partnered with Cinemag step-up transformers, the DL-103R was a great performer, offering plenty of hi-fi goodies - soundstaging, detail, etc - at a budget price.  It really is an excellent low output moving-coil alternative to the more expensive units out there.

Sadly, the cantilever of my DL-103R was accidentally broken when I moved to my new house - don't ask!  Since this new place is just temporary and has the misfortune of a smaller listening space where I cannot use the UREI 813A speakers, I instead opted to buy the budget DL-110.  Regarding type and specifications, the Denon DL-110 is a high output (1.6mV) moving coil cartridge that can work well into a standard moving magnet phono input.  At 4.8g of weight, it's also very light and with some tonearms may require the use of the included metal plate.

Using the VPI HW19 Mark III table with a Rega RB300 arm, I was immediately taken with this cartridge.  Though it lacks some of the finer points of the modified DL-103R, it still in no slouch.  No immediate shortcoming come to mind, though the midrange is perhaps slightly forward.  Bass detail is also good and treble extension was spot on with minimal aggression or roll-off.  Detail retrieval - hall ambience, trailing edges - aren't exactly on par with the best I've heard, but once again, any sins were of omission.  So all in all, a very good cartridge for the $139 asking price.

I recently purchased a new turntable: a VPI Aries I with a JMW 10.5" tonearm.  Since I only had the Denon DL-110 on hand, I was forced to use this cartridge which had a cost some 20X less than the turntable.  Due to the light weight of the cartridge body, I as forced to add the included metal plate under the headshell.  This was a tricky operation that required much fiddling and curse words.

Even with the upgraded turntable and arm - and much to my surprise - the DL-110 did not fall on its face.  For example, Neil Young's "Live at Massey Hall" never sounded so real.  Soundstaging was deep and wide and the music - much like the real, live thing - came at you instead of hanging out behind the plane of the speakers.  There was a nice shimmer to the slightly forward midrange, while bass was low but still tuneful, giving great response with the small KEF speakers.  Treble was very extended with more detail than the old HW19 table.  I'm sure I would find more faults with the UREI speakers installed, but at least with this system, the sound was much better than anticipated.  Highly recommended for the budget conscious audiophile.!

System
VPI HW19 Mark III with Rega RB300 or VPI Aries with JMW tonearm - both with SDS Power Supply
Denon DL-110
Cardas Quadlink 5C 1M interconnects
Quicksilver preamplifier with Gold Lion 12AX7 re-issues, RCA 12FQ7s, Raytheon black-plate 5814
Cardas Cross 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s, GE 6SN7GTAs, Genalex CV4085s
Kimber 8PR/4PR 2M bi-wire cable
bi-wired KEF iQ30 with VTI UF29 stands
VTI BL503 equipment rack

Sunday, March 24, 2013

New turntable: VPI Aries I


This was an unexpected purchase since recent events have cut back on my audio acquisitions.  But this was one deal that I couldn't pass up.  Featuring a thick MDF plinth, the heavy-duty metal platter from a TNT table, and a JMW 10.5 tonearm, the Aries is one heck of a piece of engineering.

I've always been impressed with the sound of my old HW19 Mark III turntable and though the Aries would only be a minor step up in quality.  But even with the only cartridge I currently have - the Denon DL-110, I heard a major improvement.  With the Aries I the background is quieter and blacker with less of a washy sound.  Bass goes lower and with more impact, while detail and treble quality has also improved.  I obviously need to upgrade the cartridge, so this isn't a real review, but more of a revelation.  I've always distrusted solid plinth turntables, intellectualizing the superiority of suspended designs.  But I guess with enough mass loading, a great tonearm, and a heavy platter, the more "primitive" solid plinth designs can compete.

More later when I've had time to process the changes and have a better cartridge installed.

Monday, February 25, 2013

Rebuilding a pair of Heathkit W-2 tube amplifiers

 The Heathkit W-2M amplifier is a fairly rare beast compared to the more later versions of the Williamson line of amplifiers.  It is also perhaps one of the earliest incarnations of a commercial ultralinear circuit.  The earlier predecessor, the W-1, used 807s connected as triodes, with pretty much the same power supply and driver circuitry.  Of note, it's would be an easy project to convert the W-2 to match the W-1, since the layout and even the output transformers are so similar.

Anyway, for my W-2 rebuild I decided to stick with a retro-modern ethos: keep the same circuit but improve the parts and biasing method.  Since I consider myself a bit of an audio historian, I prefer to hear the amplifier as the designer intended.  If someone wants to tackle an improved Williamson design, I would strongly suggest the Chimera Labs modification which will also reduce distortion, provide cleaner power, and improve square wave performance. 

(right click and open to see more detail)

Power Supply Chassis: The stock power supply is rather anemic with barely enough capacitance to reproduce transients and extended output levels.  In my case, I replaced all of the electrolytics, also increasing the values except for the first bucket since it is attached to the 5V4 rectifier.  I also added bypass resistors to normalize the voltage between the two series capacitors.  Parts required per unit: (2) 22uF/350V capacitors, (2) 150uF/450V capacitors, (4) 470k/2W resistors, capacitor mounting hardware, and nuts & bolts.

(right click and open to see more detail)

Signal Chassis: Once again, new electrolytics, also increasing the values to improve power supply stability.  Potentially leaky paper coupling capacitors were replaced by new film units.  The input capacitor was removed and replaced by a small value (1K) carbon composition grid stopper resistor.  Aged resistors should also be checked to see if they are within specification.  This is especially important for the ones requiring matched pairs.  Parts required per unit: (2) .047uF/400V capacitors, (2) .22uF/600V capacitors, (2) 1K carbon composition resistors, (1) 47uF/450V capacitor with clamp and nuts & bolts, and (1) 22uF / 450V capacitor with two lug terminal strip for mounting.

 (right click and open to see more detail)

Bias Supply: The 1/4" phono test jacks were replaced by easier to use banana jacks and 10 ohm resistors which now allow the output tubes to be balanced by using a multimeter: set the meter to the lowest voltage range and adjust the 100-ohm potentiometer until a reading of zero is found.  This biasing method is pretty much straight from the Heathkit W-5 schematic and is much easier than trying to juggle current meters with the clunky phono jacks.  Parts required per unit: (2) 22uF / 150V capacitor, (2) 10 ohm, .5W resistors, (2) banana female jacks with washers and nut, and one terminal strip.

Miscellaneous: The stock RCA jack can easily be replaced with a modern gold-plated unit.  On the other hand, the single speaker screw terminal strip is a slightly more difficult proposition.  At this time I don't have an easy solution that doesn't require a drill press and new hardware.  For now I suggest using speaker wire with small "vintage" spades, or bare solid-core wire.


Listening results: The stock pair of Heathkit W-2s, even with ancient electrolytic capacitors, were still quite pleasant.  They sounded a little muddled and lacking in power, but still possessing a musical charm that many modern units have a hard time matching.  The excellent Peerless output iron certainly helps.  However, this simple upgrade really helped, making the bass firmer and the dynamics better; all while keeping the golden midrange and easy going treble detail.  With new parts, the W-2s really excel at musicality and now rate among my favorite vintage amplifiers.  At least in my listening situation, I would still give the nod to the Eico HF-60s, but that's due to the higher power and the overall sound of the EL34, which is a tube I prefer over the 6L6GC family.  But for a different listener and a different setup with more efficient speakers, it really would be a matter of personal preference.

Tubes: With the rated 4A filament supply, it is possible for the power transformer to handle an output tube with a little more heft than the 6L6GC.  Since I'm not one to trust vintage iron too far, I probably wouldn't go beyond a KT66 type.  I would be curious to see how a set of Gold Lion re-issue KT66s would stack up against the vintage Tungsol 5881s.  Another option for the cheapskate would be to rewire the output sockets to use the 6AR6 which is still cheap and plentiful.

With two 6SN7s handling gain and phase-splitting duties, there is a vast world of tube-rolling opportunities here.  For now, I'm sticking with GE 6SN7GTAs since they are easy to get and sound great for the dollar. 

The 5V4 rectifier can be replaced with the 5AR4 which will slightly bump up the voltage and offer some of that classic Mullard sound.  However, with the high price of good vintage versions, one may want to stick with the more common 5V4 with all the various manufacturers and versions.

Conclusion: Bringing an old tube amplifier back to life and ready for another twenty (or more) years of service is always a feeling of accomplishment.  The Heathkits aren't the easiest to rebuild, not with some of the strange capacitor can sizes and small interior chassis depth, but the time and work was worth the effort.  These are wonderful amplifiers with that vintage smoothness but still modern enough for electronic music and pop.  Highly recommended.

Tuesday, February 12, 2013

New Project: a SE 6CB5A amplifier

After the completion of my 1625 "Command" amplifier, I began to cast my eye around for another project.  This time I wanted to yet again tackle a triode amplifier, perhaps doing a push-pull 2A3/6B4G type.  However, the pesky cheapskate that lives inside my head just couldn't spend that sort of coin on a set of output tubes.  While searching around, I read a thread on diyaudio that lead me to this blog post on Vinylsavor.  Check it out for the signal schematic.

The 6CB5A is a 1950s television sweep tube that wasn't designed specifically for audio, but the curve traces in triode mode are quite good.  This cheap tube can also produce 6-8Ws in single-ended, which is pretty close to the mojo of a 300B.  I also liked the idea of using the 6N7 driver, thought I opted to not implement the expensive interstage transformer, and instead went with RC-coupling.  Hey, this is a budget build after all.

Output and power iron will be from Edcor - I really liked the quality of sound I got from them in the 1625 amplifier.  Chokes will be from Triad and the rest of the parts will be standard bog stuff you can get from Mouser, Allied, and Digikey.  I've also opted for some current meters to monitor the health of the output tubes.


Since a single 6CB5A takes a mighty 2.5A @ 6.3V to light up, I had to purchase a separate filament transformer to power the 6N7 tubes.  Other than that, this is a pretty standard power supply with a fake dual-mono separation for the two channels.

Output iron has been ordered.  Everything but the top plate metalwork has already arrived, so I will provide another post when all the parts have come in and everything has been wired together.  I'm quite curious to hear what this amplifier sounds like since the build/design approach is much different than the 1625 amplifier.  The 6CB5A amplifier will have no negative feedback, a pure triode amplification chain, and minimal parts.  In my experience this should lead to a big sound with a slightly underdamped bass.  Stay tuned to find out!

New Project: Heathkit W4-AM rebuild


I didn't even get a chance to buy another Heathkit W-2, when I saw this golden beauty on Ebay.  A few bids later and I won.  Now the Heathkit W4-AM isn't exactly their best product.  There have been several complaints about the quality of the output transformer, stability issues, and the "lower rent" build quality.  Personally I think it's a lovely little amplifier and worth the time for a good restore.

The first thing to do is to replace the power supply and coupling capacitors.  After that, I plan on doing the bricktop mod to increase stability and improve the quality of the square waves.  And of course I have to score another one so I can listen to stereo.  But even with one amplifier running, I like what I'm hearing out of a completely stock unit.  I also dig the use of all octal tubes and wonder how some Gold Lion KT66 reissues would sound in there - the 4A filament supply should be able to handle the extra load.