Saturday, December 29, 2012

Review: Sansui TU-777 tuner


I'll admit that I'm not a tuner kind of guy.  The source material coming from the radio stations is usually grossly compressed and lacking any real fidelity.  The classical stations usually offer the best sound, but that kind of music isn't normally my cup of tea.  Having said that, why exactly did I buy a tuner?  Well I do any number of hobbies that often require my undivided attention.  Getting up to change the record or CD can break my concentration.  Having a radio for the background takes care of this problem and also exposes me to some different music other than my MP3 collection.

So why did I pick this tuner in particular?  It all started when I bought a Sansui integrated to fix up.  I was searching on Ebay for its radio mate when I saw this particualar model: the TU-777.  I was taken by the round tuning dial which reminded me of something from the era of classic 1930s radios.

The Sansui TU-777 is a solid-state tuner that saw its introduction to the market way back in 1968.  There are no preset buttons here!  But the dial action and signal strength meter both still work, giving a pleasant green glow to boot.  Sound quality is surprising good, much more warm and natural than I expected for something with silicon bits and aged capacitors.  It also pulls in stations reasonably well, though obviously not with the same strength as more exotic pieces.  But really, what do you want for $75?

So highly recommended - just on looks alone - if you need a simple tuner.

Monday, December 3, 2012

New project: Heathkit W-2 tube amplifier rebuild


Things are never quiet here at the 6th Street Bridge.  Having just finished up the 1625 amplifier, I decided yet another project was worth pursuing.  This time it's yet another rebuild of a vintage piece of gear - the Heathkit W-2.  This was a fairly popular "20W" mono amplifier made in the early to mid-1950s.  It uses the classic Williamson circuit with 6SN7 driver tubes, 5881 output tubes, and Peerless output iron - running in Ultralinear.  Another special thing to note is the separate chassis for power supply and the signal which is a great way to reduce hum.

The W-2  I received was in pretty good condition.  Popping the hood and the resistors and capacitors look to be in mint condition.  But sadly, the amplifier didn't work.  Not a single hum, burp, or anything out of the test speaker.  A quick diagnoses with the multimeter and it appears that the original builder had neglected to ground the two chassis together via the umbilical cord!  A short length of wire, two solder joints, and music was coming out the speakers.  It makes me wonder if I was the first to ever hear this particular amplifier.  Very weird to say the least.

Anyway, the sound - with almost 60 year old passive parts - was rather lifeless: undynamic with some treble roll-off..  Here's hoping that some coupling and power supply capacitor upgrades will bring this old amp up a couple of notches.  Of course I also need to score another unit so I can listen to stereo.

Friday, November 30, 2012

Project: The Command 1625 tube amplifier


Introduction:
In the world of single-ended amplifiers, the venerable triode still gets preference.  It's easy to see why since the 300B, 2A3, 845, and 211 - among many others - has a certain catchet and a sonic signature that is honestly very hard to beat.  The triode is quite the linear device with the downside of needing a bunch of voltage and current to make relatively low power.

The other option when running single-ended, minus the odd solid-state design, is to use a pentode/beam-tetrode in ultralinear or native operation.  This not only gives plenty more power, but these tubes also have the benefit of being inexpensive to buy.  Based on my experience with various SE amplifiers, most of the magic of single-ended is the circuit simplicity - no phase-splitter - and the Class A output stage.  Now this design I'm about to introduce was not meant to be an assault on the very best amplifiers, but instead offer a budget alternative to the sometimes stale and now very mundane 300B amplifier.  It's also an attempt to replicate 1930/1940s technology' but with modern components.  Much of the 'sonic footprint' of those pre-war years was not from inferior amplification, but the bandwidth limited source material. 

Of course running in pentode mode requires some negative feedback - a new fangled concept back then - in order to reduce the output impedance to something that modern speaker can use.  An alternative would be to experiment with Schade feedback - taking voltage from the plate of the output tube and tying it to the plate of the input tube. 

Tubes!
The first decision was tube choice.  If I wanted to be just a cheapskate, there are plenty of TV tubes that could be used.  Instead I went with a vintage classic that is still widely available - the 1625 output and 12J7 driver tube.  (Note that the 807 and 6J7 can be used - just don't use the voltage doubler for the filament supply.)  Expect to pay $5-$10 per tube, which is a bargain considering the quality of these vintage beam tetrodes.  Also note that the 1625 has a low screen voltage maximum, so running ultralinear isn't an option unless one can live with reduced voltage and the resulting lower power output.

The UX7 base top-plate cap 1625 is part of the famed 807/6L6GC family and was used in WW2 to provide radio communications - the AN/ARC-5 Command transmitter - for the majority of the planes in the United States Army and Navy.  This tube was made to military specifications with wonderful assembly and a high quality control - when it came to radio pilots lives were on the line. Since there was a war on, scads of them were made and every example I've seen is an impressive piece of engineering.  In tribute, I have given this project the name 'The Command 1625'.

The grid-cap 12J7 pentode is the 12V filament version of the 6J7 tube which is the octal version of RCA's earlier 6C6 tube, which in turn was their answer to Western Electric's famed 310A.  These tubes take the signal voltage and bring it through the cap on top of the tube - a nice way to keep the fragile signal away from noisy power supplies.  The 6J7 eventually begat the 6SJ7 which eventually became the smaller EF40/6AU6/EF86 types.  The 12J7 was selected for the fact that NOS versions are still cheap and plentiful in metal or glass versions.


(right click to open and see larger version)

A quick look at the signal schematic shows nothing too exciting, though using a pentode on the front end is considered a heresy these days of current sourced triodes and LED biasing schemes.  My idea was to keep this design as simple as possible - in the spirit of the vintage tubes selected - with minimal parts count and matching required.  Eagle-eyed reader will note that this same type of front end was used on my EL156 amplifier.  It's a good sounding front end so it was easy decision to use it again.

The feedback resistor for a 4-ohm output transformer is 6.8K.  For an 8-ohm secondary, increase the value to 8.2K.

(right click to open and see larger version)

For the power supply I stuck with tube rectification which has less switching noise than solid-state and better visual aesthetics.  The 5Z3 - a precursor to the 5U4G - was selected on looks and the decent prices, plus the ability to easily handle the current requirements for two output tubes.  Plenty of other options are available here.  Two Triad chokes and a smattering of generic capacitors provide the raw filtering for the output tube plate.  Of interest is the regulation for the screens of the 1625 and the input stage.  This stiff front end gives more control and separates it from the wranglings of the output stage.  For easy implementation, shunt regulation is accomplished with simple VR tubes: the OD3 and OC3 are put in series for 255 volts.  The small bypass cap here is just to clean up noise - going for a larger value will cause instability with these types of regulators.

The voltage doubler circuit is used to take the 6.3VAC filament tap and boost it up to ~12VDC required for the 1625 and 12J7 tubes.  Note, do not ground the center-tap.  If one wishes to use 807s, 6L6GCs, 5881s, or KT66s along with a a 6J7/6SJ7/EF86 input tube, the voltage doubler can be skipped.  In this case, do ground or lift the center tap of the 6.3VCT winding.


Parts:
Some of the passive-parts decisions were based on what I already had in stock.  For example, the PEC volume control, Wima coupling caps, and power supply electrolytics were chosen because I just happened to have them in my stash.  Builders can select their own goodies, provided they meet the electrical requirements of the circuit.  Other than that, I went with Kiwame and carbon-composition resistors, Nichicon cathode bypass capacitors, and a few Solens.

For the the output transformers I went with the Edcor CXSE model.  Alternatives are James, One Electron, or even Hammond.   For those on a tight budget, there are cheaper alternatives, but these will limit bass and treble response, not to mention that the core will be taxed more heavily.  I've found that overkill output transformers lead to a more relaxed, transparent sound.

Top aluminum panel is from the steadfast Front Panel Express.  Size was selected since I already had a leftover wooden chassis from an older project.  Layout was done to minimize power and signal circuitry interaction, while also giving a vintage "juke box" aesthetic.


Potential modifications:
Different Output tubes: With socket changes and 6.3VAC from the transformer instead of the voltage-doubler filament circuit, the 807 or any of the 6L6GC family can be used - 5881, KT66, 350B, etc.

Different input tubes: With wiring changes: the 12SJ7.  With filament and/or socket and wiring changes: 6C6, WE310A, 6J7, EF86, EF80. 6AU6, EF37, etc

Different rectifiers: 5U4/G/GB is the Octal version of the 5Z3.

Listening Results:
Turning on a new, freshly built amp is always an exciting moment.  With the test speakers - Pioneer SB-21s - place on the ground, I was immediately taken with the fast quality of this amplifier.  After checking over the power supply voltage and bias readings, I moved on to my main system consisting of Spica TC-50 speakers, a Quicksilver full-function preamplifier, and a VPI HW19 Mark III turntable with a Denon DL-110 cartridge.  This is a smaller, more budget orientated system than the setup at my old digs, so I'm still feeling my around the various changes.

First impressions - revealed an amplifier with a nice, neutral midrange.  This is not a romantic sounding unit but I would never mistake it for solid-state either.  Bass quality was very good: controlled and with no tubbiness.  This is hardly a surprise due to the heft of the Edcor output transformers.  The already mentioned speed was evident in the treble too - giving a slightly lean presentation which may be more a character of the Spica TC-50s than anything else.  Soundstaging, also strong point of these speakers, was wide and deep.  Texture and inner-detail was also top-notch.  With more dynamic music, the amplifier had no problem delivering the power while keeping everything in line.  This amplifier sounds much more powerful than its expected 10Ws, indicating good clipping characteristics common with Class A output stages.

Overall, I would still give the overall nod to the EICO HF-60s, but those monoblocks usually cost three or four times as much, and also sport much more exotic output iron plus increased power output.  Having said that - and it's always difficult to fairly judge your own creations - the Command 1625 amplifier offers great sonics for such a low price point.  It is also a great reminder that pentode outputs can compete in the world of hi-fi.

Parts list and Front Panel Express file are available upon request.  Shoot me an email.


Sunday, November 25, 2012

Acrosound 20 amplifier update


 The job of updating the Acrosound 20 monoblock amplifier became much easier once I saw a PCB for sale on Ebay.  It's a modern iteration of the same circuit, but with all new resistors, capacitors, and tube sockets.  Replacement was an easy job and with all the leads soldered into position, the amplifier fired right up on the first try.  Now that's always good news.

Some new power supply capacitors are still needed, but I'll wait until I have another matching amplifier before I make that move.

Listening in mono through a fairly efficient test speaker, it's a pretty good sound amplifier.  The Acro has some of that general "Class A" sonic footprint - an ease and naturalness to the music that makes tubes worthwhile.  It does run quite hot, and appears to be exceeding the maximum plate dissipation of the 6BQ5/EL84, but hey, this is a cheap little tube, so no worries there.  Buy 'em cheap and burn 'em up!


Review: Spica TC-50 speakers

A new house has forced me into a smaller listening room.  Since the full-range sound of the UREI 813A speakers would overwhelm this new space, I decided for an interim, ultimately deciding on a pair of mini-monitors placed on stands.

The Spica TC-50 was a popular budget mini-monitor speaker from the 1980s.  Featuring a sloped 45 degree front, a 6.5" woofer and a small tweeter, it is renowned for it's imaging capability.  Part of this performance is from the time-aligned drivers (from the sloped front) and the special crossover with matched drivers.  Of course such now vintage units suffer from aging components and drivers that are long out of production.


I bought my pair via Ebay for $250 and purchased the 29" VTI speaker stands via an online seller.

Going from a massive full-range speaker - sporting a time-aligned 604 driver combined with a 15" woofer - to a small mini-monitor takes some time getting used to.  Of course the majority of this change is the considerable lack of dynamics and bass extension with the smaller speaker.  It's simple physics - a 6.5" woofer just can't move the same amount of air as two 15" drivers working together.  In comparison, this lack of "slam" and macrodynamics makes the Spica sound rather thin.  For example, on Pink Floyd - Dark Side of the Moon, the sense of urgency as the music shifts into overdrive is essentially lost.  Simpler recordings, like The Immortal Otis Redding fare much better.

However, there is one area that both the UREI and Spica meet - it's the driver consistency - that sound of being cut from the same cloth.  Much of that has to do with the time-alignment since the output of the drivers meet the ear at the same time.  It's a hard effect to describe, but you know it when you hear it.  This is part of the reason that I enjoy KEF Q series speakers.

Anyway, at reasonable levels treble extension is fairly non-irritating though lacking in the best shimmer and detail.  The Spica does sound slightly tilted in this range, though part of that could be the comparison to my previous speakers.


The midrange is the strongest point - though not quite in electrostat territory, it's also no slouch in this department.  I tend to think "Poor man Quad ESL-63" performance.  This leads to good soundstage width and depth, though my old Magnepan 1.6QRs and even the UREIs, with their massive box, had a more realistic scale.  Vocal presence is quite good, though not scaling the heights of the best I've heard.  However overall coloration is still quite low - low enough to be called 'audiophile'.  A good example of the soundstaging depth and relative neutrality can be heard on Willie Nelson - Stardust where the location of the instruments and the vocalist are easily determined.

Bass, as to be expected, is the weakest point.  A decent subwoofer here would improve the sound, freeing the woofer from doing the heavy work.  Stock, it's sort of there, not going particularly deep.  I've heard more extension from the little, but thoroughly modern, KEF iQ30, which coincidentally also sports a 6.5" driver.

So what to think of the Spica TC-50?  It's a good little budget design that may have been a real champ in earlier days.  If you come across a pair for a good price and they haven't been modified, then go ahead and take a chance.  Having said that, a few more dollars will get you a KEF (or other) monitor speaker that will have a warranty, new capacitors, and drivers that can be replaced if you get a little out of control with the volume levels.

System
VPI HW19 Mark III with SDS Power Supply
Rega RB300 with Cardas wiring
Denon DL-110
Quicksilver preamplifier with Mullard short-plate12AX7s, RCA 12FQ7s, Raytheon black-plate 5814
Cardas Cross 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s, GE 6SN7GTBs, Genalex CV4085s
Cardas Hexlink 2M speaker cables
Spica TC-50 with VTI UF29 stands
VTI BL503 equipment rack

Tuesday, October 9, 2012

A new project: a 1625 single-ended amplifier

(picture from Google Images)

I've resisted the siren call of DIY audio for far too long.  Since my busy mind is always in need of some new project, I've decided to once again tackle a SE amplifier.  For this undertaking, I'll go for a budget build, using easy to get tubes with a vintage flavor.  With a total price of under $600, Tte 1625 immediately sprung to mind - this is the 12V filament version of the famed 807, the precursor to the 6L6GC.  Instead of Ultralinear or Triode, I've also decided to try out true Pentode operation.

I'm normally a triode or ultra-linear guy, but way back in my college days, I was walking along the sidewalk in the nasty neighborhood I was living in at the time.  Ahead I saw a Magnavox stereo console out on the curb.  A peek at the back and I saw tubes.  With a little determination out came a little 6BQ5 amplifier with a pair of tiny open-frame output transformers.  A SE amplifier!  I brought this little unit back home, installed some RCA jacks, and soon had the amplifier up and running.  The sound, for only 5Ws of power, was amazing.  Sure, the low bass wasn't there, but there was a rightness to the music - especially the critical midrange.  Not bad for a hunk of roadside trash.  I ended up selling the Maganvox unit off to a friend where it was dubbed the "5W wonder". Yes, at the time I got better results with 2A3s and 300Bs in single-ended mode, but they had the benefit of better iron and passive components.  After all these years, I'm still curious to see how a pure pentode amplifier with good parts will sound.

Of course it will have my usual tricks and favorites: tube rectification with the vintage 5Z3, screen regulation using VR tubes, a pentode input tube - the 12J7GT, and DC on the filmanents.  So far I'm leaning towards Edcor for the output transformer with Hammond and Triad power and choke iron.  Other parts will be KOA resistors, Wima coupling caps, Nichicon electrolytics, and whatever else I can scare up from my depleted junk drawer.

The initial schematic is already done, but may not survive once I get the first prototype up and running.  So stay tuned for further updates when  I will make the parts list available, along with the Front Panel Express metal layout, and final schematic.  I will also try to include a step-by-step construction guide, but I usually get a little carried away when building a new project!

Update: Amplifier built - schematic and results.

Friday, October 5, 2012

New Room, New Stereo Changes

 
Due to some future job changes, I've sold my current house and have moved into some temporary rental digs.  It's still a house, but a little smaller than before.  I have a listening room of sorts, but due to the smaller room, the UREI speakers are being put into storage.  Instead I have a pair of vintage Spica TC-50s coming in the mail.  Though these will lack the punch, bass, and pure "wow" factor of the big UREIs, this little monitor is still time-aligned and known for its imaging capabilities.  Review coming soon.

The fear of moving a stereo from one location to the other is the chance of something being broken.  I made the mistake of keeping the Denon DL-103R cartridge attached to the tonearm.  A slight accident, even though the tonearm and removable base was moved separately, caused the cantilever to snap.  It was due for a replacement anyways, but it still hurt.  Since I've gone to smaller digs and less revealing speakers, I've opted to try the Denon DL-110 high-output moving-coil cartridge.  Review coming soon.

And since the overall system is being compromised, I've also decided not to burn up my vintage Mullard XF2 EL34 tubes and will be running something a little more modern.  I have a two quads of Shuguang EL34s which sound half-decent with the EICO HF-60s.  These, and a pair of Hitachi 5AR4s, will be put into service until the listening room situation improves.

On another note, moving the UREI speakers up a flight of stairs required three relatively strong guys.  Each speaker had to be strapped to a dolly and then wrestled up step by step.  Having a low trailer was also useful since tipping them up on a high 4X4 pickup truck would damage many backs.

Tuesday, September 4, 2012

New Project: Acrosound Stereo 20 Monoblock


Stereo 20 monoblock?  Say what now?  Well, back in the early days of stereo, many audio nuts were still using mono systems or saving up their dollars to buy another amplifier.  A single monoblock was often cheaper than a stereo amplifier, giving a budget route to building up a true two-channel system.

 
In this case, the Acrosound 20 is exactly one-half of the (slightly) more popular 20/20 amplifier.  There was even a 20A model which has no power transformer but instead gets its B+ and filament voltages from the 20 Monoblock octal socket.  Very strange indeed.

 
I bought this little unit on Ebay.  It's a pretty funky, but pretty in that 1950s vintage audio way - a nice hammertone paint job with some bling gold transformers.  The circuity, except for the input caps, is DC coupled using a 12AX7 and a pair of 6BQ5 transformers.  The PCB is mounted on top, ala Dynaco style, but a small cage can be used to stop prying fingers from being electrocuted.  Output taps are 4-8-16-32, which should work with any crazy combination of speakers, provided just 18Ws of power is needed.

Of course I will have to be patient to find another monoblock - or even the more obscure 20A - but this should be a nice little project to tide my audio nervosa over for a few weeks.  No, I'm not expecting it to compete with the EICO HF-60s, but a pair of Acrosound 20 amplifiers would be a great basis for a second system.

Update: New PCB board installed.

Thursday, July 12, 2012

Review: Eico HF-60 tube monoblocks


Introduction
EICO, unlike McIntosh, Marantz, or Fisher, isn't quite spoken with the reverent tones with discussing the best of the vintage amplifiers, but to do so would be a mistake.  From their budget units, up to the the flagship model, the HF-60, they represented a serious competitor to Heath and Dynaco, offering good value for the hobbyists of yore.  When I had the rare and unexpected chance to buy a pair, I went for it, knowing I would be hearing with one of the best EL34s amplifiers around.


The Amplifiers
So what is an EICO HF-60?  It's a monoblock amplifier - requiring two for stereo - featuring 5AR4 tube rectification, the classic Mullard 5-20 circuit with an EF86 and 6SN7 driving EL34 output tubes in Ultralinear, fixed bias, and the legendary Acrosound TO-330 output transformer.  There's nothing tricky going on here circuit-wise: current sinks, current sources, regulators, dc filaments, etc are non-existent, but component quality is still quite high with wirewound resistors, good tube sockets, and a really nice hunk of iron.  Biasing is through two pots: one to balance between output tubes while the other is raw bias.  These came as very basic kits with no circuit boards: the end-user was expected to be experienced enough to do point-to-point wiring.

Another thing to note is the high plate voltage and bias, making the HF-60 run steep Class A.  500VDC on the plates with 65mA means the EL34 output tubes are running 32.5Ws (plate + screen) of dissipation, right on the bleeding edge of their maximum rating.  If the lights are off, a faint red glow can be seen on the plates(!) which, according to the manual, is considered normal operation!  Back in the day, this was no big deal since you could pop down to the local store to pick up your new set of Mullard EL34s, but now with the high price of quality old-stock tubes, a user of this amplifier may want to dial back a few milliamps.


Not Quite Stock
Before I go and describe the sound of these amplifiers, I would like to mention that mine aren't exactly stock.  Of course these days it's hard to find a vintage tube amplifier that sports its original power supply capacitors, but my set of EICO HF-60s came with some additional modifications that will effect the sound.  First off was the addition of a small choke in the power supply.  The original just used 40uF of electrolytic to clean up the voltage.  Instead, I have a 25uF electrolytic bucket, followed by a 1.5H choke, and then a large 40uF Suzuki polypropolene capacitor.  This change gives a clean and fast power supply.  The second modification is to the EF86 input tube which now uses a battery to supply the bias.  This was done by the local "tube guru" and is purported to clean up the treble and whatnot.  Original coupling caps have also been replaced with MIT RTXs and some Jantzen Z-Superiors.

Tubes used for this review: Genalex CV4085, GE 6SN7GTBs, Mullard XF2 EL34s, and Hitachi 5AR4s.


First Impression
Expectations were high when I dropped the needle on Side 2 of Supertramp's Crime of the Century.  I've often been disappointed by audio purchases since the hype doesn't often live up to the reality.  In this case I had nothing to fear - within seconds I recognized that the EICO HF-60s are something special.  They really gripped the UREI 813A speakers hard, delivering power in an effortless way, all while casting a big, deep and detailed soundstage.  It thoroughly demolished the budget wunderkind Yaqin MC-10T, and my memories of other tube amplifiers - the Dynaco 70, Dynaco Mark IV, Dynaco Mark III, Harman Kardon Citation V, Heath UA-1, various Scott, Heath, and EICO integrateds, and anything else that I missed over the years of this crazy hobby.  The EICO also beat out my now departed Threshold S/500 or any other solid-state amplifier I've owned (which hasn't been many).


Listening Notes
Okay, enough gushing already, eh?  In order to give some further insight into these amplifiers, I invited a fellow longtime audiophile friend over to listen, hoping a second set of ears would keep my effusive praise somewhat in check.  After spending a chunk of cash it's easy to get carried away with new gear, missing the warts and blemishes of music reproduction.  We listened to a number of records and this is what we heard:

Steely Dan - Aja:  Recorded by Roger Nichols, Aja's technical prowess - both musically and sonically - is laid out perfectly with the UREI speakers.  The bouncy dynamics are engaging and fun, with plenty of little details to keep the brain locked into the music.  At no time do the amplifiers run out of power - delivering the power effortlessly. 

Grateful Dead - Terrapin Station:  Side 2 of this album is a sorta short rock opera with bits of Renaissance-inspired flourishes and backup vocals.  Yeah, it's a little cheesy at times, but still well-recorded with big dynamic shifts that sound diminished with lesser speakers and amplifiers.  Needless to say, the EICOs passed with flying colors, keeping everything locked into place without ever sounding strained. 

Faces - Long Player (German pressing):  Not exactly an audiophile recording, the Faces good-time boozy musical party record sounds better than I ever heard it.  Every instrument is audible, standing by itself in the soundstage without getting lost in the thick mix.  

Supertramp - Crime of the Century (British pressing): before I got the UREI speakers, I always considered Supertramp to be lightweight rock 'n' roll music.  But with the right system, the darkness of the music becomes more apparent.  Once again the dynamics and bass impact was amazing, as was the midrange and treble detail.  Soundstaging was deeeeeep, making my listening space sound like a larger than the confines of the walls.

Fleetwood Mac - s/t: Back when I was a kid, I pretty much loathed this 1975 album whenever my parents would play it.  But changing tastes and Stevie Nick's wonderful voice on Rhiannon changed my mind.  On this system, the high production values were evident, along with various multi-tracks used to create this sonic gem.

 
Sonic Scorecard
Bass: For the longest time, the king of bass reproduction was my Threshold amplifier.  250WPC with a huge amount of available current and the high damping factor helped to give some of the most fluid and detailed bass response I had ever heard.  A known limiting factor of tube amplifiers has always been - at least in my experience - the slightly sloggy and underdamped bass.  But somehow through the Acrosound TO-330 output transformer, those normal limitations are no more.  Low frequencies are extremely accurate, controlled, and easily equal that of the massive solid-state Threshold.  Amazing for a tube amplifier.

Midrange: They actually reminds me of an DIY amplifier I built a few years ago - a SE 300B design with a hefty SV83 pentode driver.  The same kind of speed and snappiness, along with a natural reproduction of vocals, guitars, and everything else that dominates the most important part of the frequency range.  No fine sand or loss of detail, but just a natural but uncolored presentation.

Treble: At my age, my hearing of highest frequencies isn't what is used to be, but still there was no sign of harshness or glassiness.  I may niggle here and there and say that I've heard better - the above mentioned SE 300B design comes to mind or my SE EL156 amplifiers - but this is very fine hairsplitting indeed.  Cymbals have a nice shimmer with natural decay while synthesizers snap and howl like the real thing.

Soundstaging: Deep, wide, and layered with everything sitting properly in it's place.  At no point did the sound ever collapse or shorten like I've heard with several other amplifiers with undersized power supplies and output transformers.

Detail: I'm no hyper-detail freak, but the EICO HF-60s certainly didn't fog over the sound with a "tubey" mush or give fake information by cranking the upper-mids on up.  Also different recordings sounded, well, different instead of congealing into the same tonality.  I've heard plenty of tube amplifiers that suffer from "too much character", making every record sound as if it was recorded in the same studio.

I'll also note that I did some brief listening on the Magnepan 1.6/QR speakers and got great results, but the maximum volume was limited.  Those speakers love to suck current and even 60Ws of tube power wasn't enough unless you enjoy baroque/folk/light rock music at moderate levels.


Conclusion
Okay, I hate to enthuse too much about just an amplifier since getting here has been a long journey.  That's to say that an amplifier is only part of the chain of electronic reproduction.  It took several other dead-ends and paths to finally come to this point.  First of all, it helps to have a solid front end.  Though not the best in the world, the VPI HW19 is still a solid performer, as is the Rega arm coupled to the Denon DL-103R and Cinemag transformers.  The Quicksilver is really a nice bit of kit, and none of what I'm hearing would be possible without the amazing extension, speed, and explosive dynamics of the UREI 813A speaker.  This same pair of monoblocks, especially stock, may not be quite so amazing with a lesser combination of gear.  Back in the past, I used to be amp crazy, thinking "just the right amplifier" would catapult my system from mediocre to greatness.  I've since learned that a solid front-end along with a good pair of speakers should be your first step before embarking on a path of expensive amplification upgrades.

Even though the EICO HF-60s are just a part of an overall, what I did hear from these amplifiers was a revelation.  The most amazing part was the way they delivered power.  I've owned some heavy-hitter gear in the past, but it's almost like the HF-60s "know" beforehand what wattage to deliver to the speakers.  This sense of ease in reproduction just makes you forget about the amplifiers and instead just revel in the music experience.  Yes, I've owned amplifiers that can deliver much more power, but they could never do with the finesse of this electronic antique.  Much of this has to do with the Class A biasing, but also the Acrosound TO-330 output transformers.  There is definitely something special about these hunks of iron.  It's too bad that their design blueprint has been lost in the mists of time, though I'm sure some of the best offerings from Tamura, Magnequest, Tango, etc could match their performance.

It's been a long journey but I'm happy to say that I've finally found a pair of "keep for life" amplifiers.  Until I hear something better at his price point - which may be possible - I will instead turn my attention to improving my turntable, stock up on my system's tube needs, and keep buying records.


Main System:
VPI HW19 Mark III with SDS Power Supply
aluminum rebodied Denon DL-103R
Rega RB300 with Cardas wiring
Cinemag CMQEE-3440A in custom aluminum box
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate12AX7s, RCA 12FQ7s, and a Raytheon black-plate 5814
Cardas Quadlink 5C 1M interconnects
EICO HF-60 monoblocks with Mullard XF2 EL34s, GE 6SN7GTBs, Genalex CV4085s
Cardas Hexlink 2M speaker cables
UREI 813A speakers
VTI BL503 equipment rack

Friday, July 6, 2012

Review: Koss Pro DJ100 headphones


I do plenty of headphone listening at work.  It's a necessary evil when trying to program in a noisy open office environment.  Sure, I could spend some big dollars on a really nice headphone rig, but due to the amount of foot traffic have instead opted to go the budget route.  Since my old Sennheiser HD-201s have started to sometimes drop the left channel (wire) and the ear cups are deteriorating, I thought it best to buy something new.  After trolling through the Amazon website and reading multiple reviews online, I decided on the Koss Pro DJ100.  At under $50 a pair, I wasn't expecting much, but was hoping for some upgrade over the lower priced Sennheisers.

Opening the package revealed a well-made headphone that looks rather retro-futuristic in an old-timey operator sort of way..  Comfort is fairly good, though perhaps a little tighter than my old Sennheisers.  The coiled speaker cord is quite thick and reminds me of something from the 1970s.  More on this later since it turned out to be a sore spot in real life.

Audio quality: listening to several sources - PC, iPad, iPhone, and my home studio gear - revealed a headphone that lacks the deepest bass or highest treble, but has a fairly relaxed midrange.  Yes, it doesn't have the most detailed or deepest soundstage, but the forward midrange character is great for rock 'n' pop.  I'm reminded of the Grado SR60i, but in comparison the Koss headphones are lacking a little in the finesse department.  Sure, the music is there and all, but the notes are a little muddled and slapped together with the other instruments.  I certainly wouldn't use these for mixdown work since picking out the different tracks is a little more difficult compared to the Grado.  But the overall clarity does seem higher than the Sennheiser HD-201 headphones with a cleaner, less muddy sound.

My biggest complaint, however, is the damn coiled speaker wire.  Since I do the majority of my listening at my desk, I do plenty of typing.  Somehow I cannot find a comfortable place to put the wire and the constant intrusion into my arm or side is highly annoying.  The speaker wire for the Sennheiser is small, light, and long which gives plenty of places to tuck under the keyboard and monitor stand.  But the shorter, thicker and coiled wire of the Pro DJ100s is currently pressed against my elbow.  No matter how I position my desktop PC or my arms, I just can't find a comfortable, not intrusive position.  So for now, I will return to listening to the Sennheiser HD-201s and will probably end up purchasing another pair of them.

Thursday, June 14, 2012

Review: Quicksilver full function preamplifier


Introduction
Quicksilver has been around for quite some time, but their products are often overlooked for the more flashy Conrad-Johnson, Audio Research, or whatnot.  However, much like VTL, Quicksilver instead concentrates on simple but solid tube circuitry, robust old-school construction, and moderate - at least for audiophile gear - prices.  The full function preamplifier in question is the earliest incarnation of the product having first hit the street in 1988.  Price back then was a princely $1995, making it roughly in the same price range as the famed Audio Research SP-8 or the slightly later Conrad-Johnson PV11.

I bought mine from a seller on Audiogon.  Shipping was prompt and I received a very heavy duty preamplifier that doesn't quite have the same ooze of quality that ARC or McIntosh has, but certainly is no slouch in fit 'n' finish.  Cracking open the top plate grills, you will see that the power supply and signal path are separated by a thick steel wall.  Very nice.  Component quality is also good though hardly esoteric.


Circuit and Controls
A quick look over the tube complement and circuitry:  Some of this is based on guesswork since no schematic could be found.  The power supply uses a large power transformer, a pair of 6X4s which are still widely available NOS, a small choke and a number of large Mallory capacitors to provide the DC smoothing, along with some regulation for what I assume are the tube filaments.  The line stage uses one 12AX7, one 12AU7, and one 12FQ7.  Since the reported output impedance is so low, I'm assuming the 12FQ7 is being used as a cathode-follower with some negative feedback wrapped around the entire circuit.  The last bit is the phono stage which only uses a single 12AX7 and a 12FQ7 with some sort of green LED biasing.  Coupling capacitor quality is in the meh range, but hardly out of place for the era.  The big 2uF capacitors on the output stage are some REL Polyesters (ughh).  The smaller signal caps are branded Quicksilver though also look to be REL made.

Front controls are fairly standard though a little dated: No remote here!  Lighted power, AC rear receptacle switch, and a mute button make up the left hand of the faceplate.  The right side has a tape monitor switches, a reduced (20dB) gain switch, a selector switch, and a stereo/mono/etc switch.  Volume control is dual mono with one stepped Blue Alps per channel.  These actually work better than expected - with the numbered volume steps it's very easy to match levels between channels.

Rear panel is the usual assortment of nice gold-plated RCA jacks and a grounding post for the phono stage.  Power cord is captive.  Fuse Holder holds a 1A unit.  AC receptacles are a nice throwback to the days when the user would power up his amp and sources with one flick of the on button.


The Sound
Okay, enough introductions - how does it sound?  Well, since this is an older unit, the stock tubes are long gone.  For the purposes of this review I used some really nice NOS tubes from my stash, so results will vary to a certain degree depending on what is plugged into the sockets.  In my case I used early 1960s short plate Mullard 12AX7s, a late 1940s black-plate RCA 12AU7, and 1960s-era side-getter RCA 12FQ7s.  Rectifier tubes were Tungsol 6X4s.  Some generic tube damping rings came with the unit, so I kept those in place.

It's been my experience that ultra-regulated, current-sourced, current-sinked, and whatnot circuits are very detailed, but also suffer from sounding slightly unnatural.  Note that tube regulators are usually better than solid-state, while shunt suffers from less sterile sound than series.  My own DIY experiments with a simple linestage showed that pulling regulation out of the circuit actually improved overall musicality and enjoyment.  Sure, some of the last bits of inner-detail are missing, but the music usually sounds more relaxed with a looser power supply.  This type of sound was very evident with the Quicksilver preamplifier which just uses chokes and caps to provide a clean source of DC.

Compared to my old Threshold FET-10/HL linestage and Audio Sector Phono Stage, the Quicksilver (with Cinemag step-up transformers) has a relaxed presentation that draws you into the deep soundstage.  It's almost like unclenching your teeth after a roller-coaster ride, or taking a good solid gulp of your favorite adult beverage: the muscles relax and you sit back with enjoyment, washed away by the sonic swirl of the music.  A good stereo should be a psychedelic experience - an unregulated and legal high - that lets you forget the troubles of the world.  With the Quicksilver preamplifier, I feel as if my entire audio experience has been improved.


Listening Notes:
I used my turntable exclusively for this review, but the linstage by itself is no slouch either.  The Audio Sector phono stage combined with the Quicksilver was a pleasant surprise, but the Cinemag and native phono section got the nod in sound quality.

The Who - Tommy (W. German Polydor):  The Quicksilver has very excellent detail and speed, keeping up with Keith Moon's manic drumming without breaking a sweat.  Small individual instruments - like a small bell - maintained their place in the soundstage while still being audible in the wash of thundering bass and guitars.  Depth was deeeeep, making my room seem bigger than reality.

The Beatles - Rubber Soul (Japanese Parlophone): This particular cut of this famed album has been described as bright and bass heavy compared to the original British pressings, but to my ears it sounds like it was eq'd flat.  With the Quicksilver, treble is extended and detailed with out any forwardness or grit.  There is lots of nice detail with John's wonderful voice cutting through the primitive stereo mix.  It's harder to get closer to the Beatles than this.

Tom Waits - Closing Time (80s Asylum): Perhaps I'm a sentimental slob, but I love this album.  However, the Quicksilver revealed the limitations of this later pressing.  Some detail, compared to some better versions, was missing, as if the music was hiding behind a thin gauze.  Tom Waits voice, however, was still wonderful, leading to some near tears while listening to the bittersweet song Martha.

Record after record revealed a preamplifier - and stereo system - that was very analog sounding.  Perhaps somewhat lacking in some of the hyperdetailed / transparency of more modern pieces, the Quicksilver was still no slouch.  When it came to musical enjoyment, I give it an extremely high ranking since it never sounds bleached out or unnatural, even with less-than-perfect recorded music.  If you want a preamplifier that speaks to the mind instead of the heart, you may want to look elsewhere.  I've gone down that road with my foray into solid-state gear, but I'll take naturalness over artificial effects any day of the week.


Overall:
Soundstaging:  Deep and Wide, imaging goes beyond the boundaries of the speakers and even the walls of my listening room.

Treble: Airy and extended, but also pure and detailed.  Compared to the darker Threshold/Audio Sector, it seems there is even more overall treble, but yet it never is harsh or unfaithful to the record.  A strange effect and not at all what I expected from tubes and a step-up transformer.

Midrange: Glorious, but not overly slow or "tubey" in the classic sense.  The Quicksilver certainly doesn't sound like a soggy Dynaco PAS.

Bass: The 12FQ7 output tubes can swing some current while delivering a low output impedance.  This translated into control.  I certainly didn't miss the solid-state drive of my last preamplifier combination.

Speed: (or PRAT) Good tube gear isn't supposed to be sloggy 'n' slow.  The Quicksilver preamplifier and Yaqin amplifier combination certainly doesn't sound like an aged tube integrated or a Dynaco 70 in need of a rebuild.  Instead, the music transients started and stopped on a dime with no overhang.  With the UREI loudspeakers, this led to a very dynamic, exciting, but yet unfatiguing sound.

Detail: As mentioned above, the Quicksilver is no king at wringing out the very last drop of detail from the music.  No, it isn't flat or uninvolving, but the very last bits of information are perhaps less apparent than some other units I've heard.  Some of this may be due to the large Polyster output capacitors.  An upgrade is due for some of the parts - notably some new polypropolene capacitors - so it will be interesting to see what effect this has on the sound.  But really, I'm not complaining because I'll take all of the positive attributes over hearing the squeaky chair of the violinist in the third row.of the orchestra pit.


Conclusion
For a going used price of $850-$1000, the Quicksilver full function preamplifier is highly recommended.  It's extremely well-made and is very natural sounding.  Errors - and I mean minor - are ones of omission with a high scale of musicality.  The simple circuitry will minimize future troubles since there are less "moving parts" once you get rid of the solid-state and regulation support circuitry often found in modern tube preamplifiers.  I expect to increase the audio grade of this unit with some coupling and electrolytic capacitor replacement, so stay tuned!


Main System:
VPI HW19 Mark III with SDS Power Supply
aluminum rebodied Denon DL-103R
Rega RB300 with Cardas wiring
Cinemag CMQEE-3440A in custom aluminum box
Cardas Cross 1M interconnects
Quicksilver preamplifier with (real) Mullard 12AX7s, RCA 12FQ7s, and a RCA 12AU7
Cardas Quadlink 5C 1M interconnects
Yaqin MC-10T amplifier with black-plate RCA 12AT7s and (real) Mullard XF2 EL34s
Cardas Hexlink 2M speaker cables
UREI 813A speakers
VTI BL503 equipment rack

Monday, June 4, 2012

Using the Cinemag CMQEE-3440A step-up transformer


Ah, the moving-coil phono cartridge is famous for it's speed, detail, and audiophile street-cred.  Ranging from the lowly Denon line, up to multi-kilobuck units, the low output moving-coil (LOMC) requires more gain than your average phono stage delivers.  Since I recently bought a Quicksilver full-function preamplifier (review forthcoming), I needed a way to boost the lowly voltage of my Denon DL-103R before hitting the tubed phono section.  I could continue to use my Audio Sector Phono Stage into a line input, but if you're going to run a tube preamp, what's the point of letting the phono section lay fallow?

Enter the Cinemag 3440A step-up transformers.  Cinemag, once a division of the famed Altec-Lansing, has been making this inexpensive step-up transformer for some time.  Word is, coupled to the Denon Cartridge, this step-up makes beautiful music.  Since I already had an aluminum chassis, RCA jacks, switch, and ground post from a previous DIY project, this was an easy decision to make.

Here's a list of what you would need:
Solder
four RCA jacks
DPDT switch (optional)
ground post
wire cutter/stripper that can handle 26awg wire
a few nuts/bolts to hold down the transformers to the chassis
some sort of chassis, metal or plastic will work
a drill press
two Cinemag CMQEE-3440A transformers

Since I didn't want to wait the few weeks for Cinemag, I ordered at a slightly higher price from an Ebay seller.  A few days later and I received a small package with two dinky transformers, two L brackets and two screws.  With both transformers, I screwed on the L brackets, using the longest piece against the bottom of the transformer.  The other end of the bracket was fastened to the chassis into some holes that I drilled with my press.

I put in new RCA jacks and a binding post.  I was lucky enough to already have a DIY phono project that already had holes for these.  If you're not steady with a drill, Front Panel Express or some other company can do the work with a professional fit and finish.

Now comes the wiring.  I used Cinemag's wiring diagram:

Input: Brown and Yellow wire RCA input lug
To Position 1 of switch: Red and Green Wire
To Position 2 of switch: Orange and Blue Wire
From Switch, solder a single wire to the RCA ground lug

Output: Purple wire to RCA input lug
Black, White, and Great wire to RCA ground lug

Note: The switch is optional if you know you are going to just use one of the taps.  With the the Denon DL-103R, the 37.5 ohm input seems to work the best.  At least in my system.  But having the switch does allow one to try both settings.

Another Note:  This wire is thin and fragile.  I use a GB-branded wire stripper from Home Depot.  When stripping off the insulation, make sure not to pull hard on the wire.  I use a needle-nose pliers to hold a section of wire downstream, giving some support.  I would hate to yank a wire off from inside the transformer.


Okay, here comes the moment of truth:  So how does the Cinemag/Quicksilver combination stack up against the Audio Sector Phono Stage?  Well, I will save the nitty gritty for my review of the tubed Quicksliver, but for now I will say that I was pleasantly surprised by the Cinemag.  My presumption was that running the small output of the Denon DL-103R through several lengths of wire would give less detail and dynamics.  But the real world shows great performance: deep bass, good 'slam', extended treble and, as the transformer broke in, plenty of detail.

I may give the nod to the Audio Sector Phono Stage for hi-fi pyrotechnics - attributes like detail and speed.  But the Cinemag/Quicksilver has a more relaxed presentation that makes it easier to enjoy music.  Stay tuned!

Friday, June 1, 2012

Revisiting the UREI 813A loudspeakers


In my previous review of the UREI loudspeaker, I claimed:
Weaknesses? Maybe because of the large baffle area, these are not soundstaging champions. Most mixes never go beyond the sides of the speakers. Another downside is that the sound never truly opens up until these are playing very loud. This makes them unsuitable for apartment and condo dwellers. Because of this, they don't quite work with baroque music either. They are also a touch dry and unrelenting - a bad recording is well, a bad recording and they will certainly show you the weaknesses of your favorite not-so-well-mixed music.
After some extended listening with a new front end and different amplification chain, I'll take most of those words back.  With an EL34 based amplifier and my improved analog front end, I am now getting excellent left-to-right imaging that goes beyond the boundaries of the speakers.  Depth has also improved.  The EL34 coupled to the Altec 604 driver has also resulted in a smoother, more coherent sound than either the Threshold S/500 or my old Dynaco Mark IIIs using SED 6550c.  Now hearing inner-detail doesn't require the volume level to be cranked to the max which makes me happier.

Lessons learned?  The front end is the most important part of your system; concentrate on that part before casting blame downstream.  Also the UREIs are in fact very neutral speakers only revealing the flaws of your signal chain.  That is to say that modern production tubes just can't hold a candle to the old stuff, especially in the treble department.

Main System:
VPI HW19 Mark III with SDS Power Supply
Rega RB300 with Cardas wiring
aluminum rebodied Denon DL-103R
Audio Sector Phono Stage with OPA627s
Cardas Cross interconnects
Quicksilver preamplifier with (real) Mullard 12AX7s, RCA 12FQ7s, and a black-plate Raytheon 5814
Cardas Quadlink 5C interconnects
Yaqin MC-10T amplifier with black-plate RCA 12AT7s and (real) Mullard XF2 EL34s
Cardas Hexlink speaker cables
UREI 813A speakers

Tuesday, May 8, 2012

A time to rebuild my main system


Boredom?  I don't know, but I've decided to rebuild my main stereo system.  The Magnepans and Threshold gear are on their way out.  I'm currently running a stripped-down version of several bits and pieces.  The end result has been pretty good, but I'm looking to make some serious upgrades in the future.

Current Main System:
VPI HW19 Mark III with SDS Power Supply
Rega RB300 with Cardas wiring
aluminum rebodied Denon DL-103R
Audio Sector Phono Stage with OPA627s
Cardas Cross interconnects
Yaqin MC-10T amplifier with black-plate RCA 12AT7s and (real) Mullard XF2 EL34s
Cardas Hexlink speaker cables
UREI 813A speakers

This simplification has given excellent sonic results.  I'm not sure if it is the Cardas cabling, the Mullards, or the improved front end, but the UREIs have vastly improved over my past memory of them.  Soundstaging, left to right, is excellent, and now goes beyond the boundaries of the cabinets.  The treble is much smoother and playback levels now don't have to be cranked to sound good.  The sheer dynamics of the UREI speakers makes everything else I've heard sound rather weak and anemic.  Sure, planars have better depth and perhaps some better inner detail, but they don't have lifelike impact and bass extension of such a massive full-range speaker.

 
The Yaqin integrated amplifier - especially with the upgraded tubes - is still a jaw-dropping great deal.  I had way more money invested in my rebuilt Dynaco Mark IIIs, but the Yaqin surpasses that design with an easy musicality that is enjoyable with all sorts of music.  Maybe I prefer the EL34 sound over that of the harder-edged SED 6550c?

Anyways, I'm not 100% sure of what direction to take.  I'm thinking a front end upgrade - the turntable, arm, and cartridge - may provide the best results.  But I'm eying several tube preamplifiers and amplifiers, especially some of the higher wattage units.  The Threshold S/500 has given me a taste of big power, and such serious amplification gives added weight and an sense of ease to the music.  But still, the siren call of a low-powered triode amplifier is very strong.  There is also a possibility that I will go a different speaker route - Martin-Logan.  Sure, I'll miss out on some of the dynamics of the UREI, but electrostats have such definition and speed that they make every other type of driver seem slow and muffled.

Stay tuned!  There will be plenty of reviews forthcoming as I begin to explore some new gear.

Thursday, March 29, 2012

A Visit with the Grado SR-60i headphones


Okay, I'll first have to admit that I'm not a headphone kinda guy.  I use them grudgingly - mostly with MP3s at work and for mastering & mix-down, but I've never liked the experience of having such poor transducers so close to my head.  Sure, headphones don't have room interactions and some of the ills of speakers, but I've never heard a pair - even electrostatic models - that sound as good as a great speaker.  For example, with my Magnepans, voices have more realism, instruments have body and impact, which all sound closer to the real event.  With headphones, it's a shrunken version of life.  And with speakers, I can almost fall into the illusion of music, but with headphones, I always know I'm missing something.

So now that I've complained enough, where do the Grado SR-60i fit into all of this?  Well, in my little PC-based studio, I use Sennheiser HD570 headphones and a set of budget Pioneer BS-21 loudspeakers to do my monitoring and recording.  The headphones are great for those times when I don't want to bother my family or when adding the finishing touches on a recording.  I've had the 570s for quite a number of years and never really cottoned to the sound - they were always a little bass-heavy, muddy, and lacking in clarity and top-end sparkle.  So it was no great heartache when they finally broke with the right channel no longer making any noise.  This is probably just a cord issue, but I decided to buy something else with the budget open-back Grado's finally making the cut.

At $79 from Amazon, this is hardly an expensive pair of headphones.  And upon arrival, I can see why.  The mostly plastic construction feels cheap, but at least the signal wiring is quite thick.  They also don't look particularly sturdy, so we shall see how they hold up in the long run.  Comfort is okay, even with my big noggin' but I don't wear them all day.  Here I would probably give the nod to the Sennheisers which are quite easy to wear for long stretches of time.

At a 32-ohm impedance, an amplifier with some moxy will be required.  For example, some tube-only designs may not have the ability to drive these well.  But I've found the stock Focusrite Saffire 6 USB headphone amplifier and even my ancient Asus Netbook had no issue.  Listening to sources of various quality, I've found that the sound is quite 'clear' - I hate that word - compared to the muddiness of the Sennheisers.  Bass response isn't as low, but I'm no fan on the 'thump-a-thump' Stygian depths that some other listeners crave.  Where the Grado really shines is the even-handed midrange and sweet 'n' easy treble.  Music just has a more natural sound with a low listening fatigue factor.  If it wasn't for the open back design, I would gladly switch these out with my lowly work Sennheiser HD-201s - which are only used for their known cheapness, closed transducers, and comfort factor.

Highly recommended, but audition before you buy since headphones are highly personal items in both comfort and sonics.

Monday, March 19, 2012

Review: Pioneer SP-BS21-LR Bookshelf speaker



Speakers at any price point are always a matter of trade-offs, and the lesser the budget, the more compromises the designer has to make.  Designed by Andrew Jones of TAD fame, the Pioneer SP-BS21-LR is a compact rear-ported mini-monitor utilizing a 1" soft dome tweeter and a small 4" woofer.  According to online resources, Jones tried to maximize the sonic results with a custom cabinet, a multi-component crossover design, and OEM drivers.  Efficiency is an extremely low 84dB, meaning some good solid-state amplification may be the best thing around when driving these speakers.  Prices for the pair range from $49 or more, depending on the vendor.  This is hardly the dollar amount that audiophile wonders are made out of, but more on this later.

Small stands or placement on a large bookshelf would be suggested.  I use mine sitting on a table in a small recording studio, suitable for playback while playing synth, or for monitoring mix-downs.  I basically wanted something cheap, fairly neutral - or at least with a coloration that was easy to hear around - and enough toughness to handle a sudden sonic overload.  The SB21s delivered this at a price point that made my wallet breathe a sigh of relief.  Using the Dun Mei LM3886 amplifier, sonics for mix-downs was surprisingly good, sounding much like my Sennheiser 570 headpones.  The treble was smooth, the midrange fairly good, and the bass had a nice growl.  I was curious enough to give these a listen with some more serious amplification.

I pulled out a B&K ST-140 down from the shelf.  Preamp duty was done by my retired Audio Research SP-7.  Signal source was a Sony SCD-CE595 SACD player.  Wiring was Belden interconnects and Canare speaker wire.  Hardly a upscale system, but better than your average receiver.

First up was a SACD - David Bowie's Scary Monsters - a classic 1980 gem that was the last burst of Bowie's creativity before his plummet to more pedestrian pop.  Through the Pioneer Speakers, the sound was quite dynamic with good (for the speaker size) bass definition.  It is also clean and with an easy,  non-aggressive treble.  Soundstaging depth is fairly flat, but left-to-right sound placement was quite good.  Sure, the sonic results weren't close to my Magnepans or even my lowly KEF speakers, but any problems were sins of omission.  Some detail was missing and the more dynamic parts of the music were slightly congested, with a bit of wooden chestiness.  There was also some minor 'blurriness' to the images, but I've heard much worse at higher price points.  A few more discs later, and my thoughts were extremely positive about this speaker.  Sonically it reminded me of some older Dynaudio kit speakers I once owned in college, or even of some older Wharfedale Diamond Vs.

When I finally came upstairs, I mentioned to my wife that I was listening to the Pioneer speakers.  She looked surprised, commenting that she could feel the bass coming through the floor.  She thought I had been listening to the Magnepans!   Not bad at all for just a 4" woofer. 

So highly recommended - but within their limitations.  A perfect dorm or teenage speaker, it will also work well for a second system.  I would also recommend some amplification that can deliver some current, since the low-efficiency will eat up power.

Thursday, March 15, 2012

Review: Dun Mei hybrid chip amplifier

(pic from Ebay)

The Chinese audio scene is certainly interesting, with quite a number of products flooding the Ebay market.  I was initially skeptical of this gear, but the experience I had with the Yaqin MS-22B piqued my interest further, leading me to buy a Yaqin MC-10T.  So far, I've found the metalwork to be quiet good, and only find fault with some of the 'interesting' design decisions and parts quality - which I often suspect of being counterfeit.

I think the Sino tube gear market could really take off, but only if they started designing gear that was not only sensibly priced, but much more palatable to the worldwide market.  They seem to have a real love for integrated amplifiers, including ones with onboard DACs, but often lacking phono stages.  I would really prefer to see basic power amps, linestages, full-function preamps including phono circuitry, and tubed DACs - all using standard tubes.  Some of the products strike close to this ideal, but many of them are strange beasts, which could possibly turn off some Western buyers.

(pic from Ebay)

Okay then, so what exactly is the Dun Mei?  It's essentially a basic amplifier with a pair of RCAs for input, a cheap volume pot, and a 6N11/6DJ8/6922 cathode follower (aka tube buffer) driving a LM3886 chip amplifier.  Capable of 50WPC into 8-ohms, and only 68WPC into 4-ohm, this little unit won't exactly win any horsepower wars.  But in the real world there is always room for such minimal wattage - second or cottage systems, dorm rooms, and running larger desktop stereos.

Build quality is so-so.  The front panel is certainly nice looking, including a hefty volume knob and LED power light.  But the metalwork, and especially the back panel, is a little er, underwhelming.  It looks like a generic case that has been used across many different lines - capable of being a preamp, DAC, or amp.  The speaker jacks through the back lettering doesn't exactly inspire confidence either.  The interior work is a little better with some half-decent wiring layout, a blue PCB with various parts, a toroidal power transformer, and even an AC filter.  However, I wasn't too keen on the generic clear speaker wire, the use of hot glue, or the RCA jacks that were installed incorrectly, with red being left and white being right.

I admit bought this unit on a whim - a chance to check out yet another budget piece from China, and as an opportunity to hear a LM3886 chip amplifier.  The results were surprising.

(pic from Ebay)

Initial listening was done on my second system, replacing my now defunct Audio Research D-52B.  First impressions showed an amplifier with relatively light bass weight, a fairly decent midrange, and a bit of a glarey top-end.  Not great, but again, not bad.  But wait, dear listeners, the stock Chinese 6N11 tube is easily replaceable with a better 6DJ8, 6922, or 6N23P.  Since I have a few of these in my stash, I first plucked out a Russian 6N23P - a budget favorite.  The sound definitely took a turn for the better - a little warmer, but the top-end still had a tizziness that was a little annoying.  Next up was an inexpensive Matsushita 6DJ8 - basically a Japanese copy of a Mullard tube.  The rest of my listening notes was through this tube.

(pic from Ebay)

As stated before, this amplifier lacks the ultimate bass extension - perhaps I'm asking too much out of only 50Ws of power, but even the Audio Research D-52B had more weight and punch.  But the midrange is clear, erring on the leaner side of the spectrum.  This is, of course, somewhat dependent on tube selection, but so far, I wouldn't call this amp "tubey" sounding.  The top-end, though lacking the shimmer and airiness of the best I've heard, is fairly good, though perhaps a touch sterile.  I also wouldn't call this amplifier hyper-detailed.  It also doesn't envelope you with a huge 3-D soundstage or have massive depth, but it isn't flat like a pancake either.  Again, I haven't bought a vintage Amperex 6DJ8 to use here since I don't think many buyers of this budget amplifier will be using expensive NOS tubes with the Dun Mei, but perhaps a different tube would yield better results.

Okay, I'm nitpicking, comparing a very inexpensive power amplifier to some heavy-hitters, but that's life in the audiophile world.  What this amplifier does excel at is being a quiet, fairly neutral reproducer of music.  It would be great starter amp for any beginner audiophile, or anyone who needs more than basic T-amp power in a small(ish) package.  My Dun Mei ended up in my home studio, driving a pair of budget Pioneer BS-21 speakers.  The volume control is perfect for dialing in sound levels while playing, track playback, or mastering.  The sound here is neutral enough for me to hear the effects of adding reverb or effects to the final sound.

Second System:
Preamplifier: Audio Research SP-7
Amplifier: Audio Research D-52B
Analog: Dual CS-5000 turntable - Audio-Technica AT95E cartridge
Digital: Pioneer DVD-V7400
Speakers: KEF iQ30
Speaker Cable: Kimber 8PR/4PR bi-wire
Interconnects: Cardas Crosslink

Saturday, March 10, 2012

A Visit with the Audio Analogue Puccini SE


Sadly, in my second system, the Audio Research D-52B started having issues.  The right channel started distorting - leading me to believe there is some electrolytic capacitor issue or problem with the discrete op-amp module.  Since this amplifier is built so compactly, getting into the guts requires a lot of difficult disassembling.  With that in mind, the ARC amplifier and SP-7 preamplifier have been relegated to the shelf.  Searching for a replacement, I came across the Italian-made Audio Analogue Puccini SE.

How did I choose this particular integrated amplifier?  Well, a few years ago, I was taking a small vacation with my wife, staying at a very fine downtown hotel in Ann Arbor.  After visiting the local records stores, I agreed to go to a yarn shop with her.  While she went over the goods, I had nothing to do but stare off into space.  Some background classical music was playing and I noticed the fidelity out of the little wall-mounted Polk speakers was quite good.  In the corner, I saw a nicely constructed silver-faced integrated amplifier.  Some closer inspection revealed the manufacturer - Audio Analogue.  Somehow that experience stuck with me and was filed away.

I bought my Puccini through Saturday Audio Exchange, which is, coincidentally, the place in 1989 that I bought my first ever preamp - a SAE Mark XXX.  Shipping was very prompt and I soon had the double-boxed amplifier in my hands.  Opening the box revealed an extremely well-built amplifier with a thick face plate and a nice heft.  With only two front controls, this is about as simple as you can get - a selector switch that includes a phono input (!), and a volume control that also puts the amplifier into standby mode when turned all the way down.  It's nice to see something so well made, especially made in Italy - which adds an additional cachet.

 
Setup was silly easy with two sets of speaker jacks per channel and a row of RCA jacks.  Turning the amplifier on and there was zero - and I mean zero - hum or noise.  Even the phono stage is dead quiet.  Initial impressions while listening to a Japanese pressing of  Haircut 100 - Pelican West revealed an extremely smooth sound.  The treble doesn't sound aggressive or forced, reminding me of some much more expensive amplifiers.  Bass output and dynamics seem a shade lighter than some other units I've heard - for example, the B&K ST-140 and ARC D-52 have more weight with the KEF iQ30 speakers.


A quick perusal of the schematic - not that I'm all that good with solid-state stuff - reveals an 5534 op-amp bootstrapped to the power supply, driving a quad of Darlington output transistors.  Power supply is dual-mono, with a toroidal power transformer for each channel. 


The phono-stage uses a 5532, with the linestage duties done by a TLE2072CP.  Not that I have anything against op-amps, since my beloved Audio Sector Phono Stage uses OPA627s, but I really was surprised by the quality of audio they managed to squeeze out of these devices.  I guess this shows the importance of layout, power supply, and circuit design, instead of just the amplifying devices themselves.

Letting this integrated warm up and I was quite pleased with the results.  As mentioned before, this unit has a real smooth musical sound. Though lacking in ultimate dynamics, the Puccini never disappoints in the finesse department.  This is a music lovers amplifier, made for a wide variety of recordings and it speaks to the heart, not the analytical head.  Soundstaging is good with a wide and fairly deep presentation, but that last bit of ultimate detail is missing.  Still, at this price point, I have no complaints.  Very recommended - especially for those who just like to spin records or CDs with maximum enjoyment, not worrying about audiophile nervosa.

Just one additional note: Some reviewers have compared this amplifier to tubes.  Beyond the smoothness, I don't quite hear it.  The Puccini is just very good solid-state, but lacks some of the dimensionality and life-like attributes I hear with some of the better tube units.

Second System:
Integrated: Audio Analogue Puccini SE
Analog: Dual CS-5000 turntable - Audio-Technica AT95E cartridge
Digital: Pioneer DVD-V7400
Speakers: KEF iQ30 on VTI UF stands
Speaker Cable: Kimber 8PR/4PR bi-wire
Interconnects: generic

Monday, February 6, 2012

Tube Rolling with the 12AT7


Since the Yaqin MC-10T uses 12AT7, I've taken to a bit of tube-rolling.  Since this is a relatively budget amplifier, I didn't want to go whole-hog and buy something hideously expensive like Brimars or Mullards.  Instead, I went the American route.  These are still priced reasonably (for now - so stock up!)  My findings so far:

The "flat plate" RCA blackplates - looks like a miniature 12AX7 plate; not folded over wing-style like all the rest, but instead two flat pieces welded together.  Very organic and even-handed with a big soundstage.  Fantastic!

Blackplate Tung-Sol 12AT7 - Although Tungsol isn't noted for their small signal tubes, they got this one right.  Much like the RCA, this has loads of detail but remains cohesive throughout the range of music.  It's a close contest here between this and the RCA.

Regular RCA black or grey "folded wing plate"-- very good and very common.  Much better than any modern production version, and if you're on a budget, the obvious choice.
 
Tung-Sol grey plate - 1950/1960s production.  Quite common.  Though lacking the sheer musicality of the best, it is still a much better tube than the stock Shuguangs.
 
Other alternatives to try out: G.E. (shudder), early Sylvanias, and CBS.  Many other brands will have been made by other manufacturers - for example, Westinghouse was normally sourced from RCA stock.