Short Review: Lepai LP-2020TI amplifier

I'm in the midst of building a small home studio for recording synth and guitar.  My plan for monitoring was to use a pair of KEF Q350 speakers with a small amplifier.  With my past love of the Charlize and other Class T amplifiers, and a low budget, I decided to give the Lepai LP-2020TI, available from Parts Express, a try.  For $25 it is hard to go wrong.  If I didn't like it, no big hit to the pocket book.

This thing is tiny - like the size of two packs of cards.  It is also extremely light; helped by the 12V outboard power supply.  Build quality is just okay.  I'm not a big fan of the spring clip speaker wire connectors or the tone controls; which can thankfully be bypassed.  The light-up volume control is gimmicky too but no real major complaints given the silly low price.

In my garage system - replacing the venerable Adcom 545 - I was surprised how good CDs from the old Pioneer DVD player sounded.  There was a toe-tappin' excitement to the music with plenty of kick.  The Wharfedale Denton speakers are a good match with this amplifier, making more volume than I expected.  There was a nice speed to the sound too.  Over all I would give the slight nod of the Lepai over the Adcom, but we are talking a garage system so let's not get too carried away!

I originally wasn't thinking of plonking this little amp into my main system, but given the amount of free time I have due to being furloughed, I decided to give it a try.  Initial impressions were rather eye opening.  This is one very nice sounding amplifier.  But a few minutes of listening, even with my Dual CS5000 and Schiit Mani phono, I could hear a loss of detail and blurring compared to the Aleph J.  Bass of the Lepai was also a little rolled off and there was some solid-state grit and forwardness on top.  But to be fair, the Aleph cost in the neighborhood of $900 to build; a far cry from the dinner-for-one price of the Lepai.

Conclusions?  It's a good amp for cottages, garages small apartments, dorms, or where critical listening is not of upmost importance.  I could easily imagine a system with a Rega RP1, Schiit Mani, the Lepai, and your favorite budget mini-monitors.  Such a stereo would best a lot of ones that I've heard (or even owned!). 

Garage System:
Pioneer DV-V7400 DVD/CD Player
Schiit SYS passive linestage
Adcom 545
Wharfedale Denton 80th Anniversary
Belden 9497 speaker cable
generic interconnects

Main System (second turntable)
Dual CS5000
Schiit Mani
Classe Five preamplifier
DIY First Watt Aleph J amplifier
KEF R500 speakers
Cardas Twinlink speaker cables
Cardas Neutral Reference and Iridium interconnects

Review: Classe Five preamplifier

 
Introduction:
Given my heavy valve past going with an upscale solid-state preamplifier was a difficult choice.  Though certainly not a heart-wrenching one as I do have more recent experiences with Threshold, Adcom, and even some homebrew gear.  And since I was considering going all separates, different preamps for both phono and line, my choice to buy a full-function Classe 5 may also be a puzzling one.

Classe, however, is one of those companies that have been on my radar ever since I was a twenty-something reading Absolute Sound and Stereophile.  Back then Classe was considered very "tube-like" and warm, completely opposite to the common complaint of much solid-state gear: harsh or strident, especially in the treble region.  Such descriptions, like the warm sound of early Mac SS gear, piqued my interest.  But since I was a poor college student, living on a diet of vintage tube amps, Mac 'n' Cheese, and $2.99 records, anything in the price range of a Classe DR-5 or DR-6 preamplifier was unthinkable. So instead I soldiered on with DIY gear, plenty of Dynaco PAS preamps, and an Eico HF-85.

Well doesn't time fly?  Perusing through the Audiogon ads, I saw a recently listed Classe Five preamplifier.  It had a phono stage, switchable from MM or MC cartridges, and even a remote control.  Their isn't much information out there on the Five but some search engine sleuthing and I found it is essentially an upgraded 1990s version of the original DR-5.  It also features balanced (XLR) or single-ended (RCA) outputs; a single set of balanced inputs too if I ever needed them.  The XLR outputs will come in very handy for my planned bridged ACA amplifiers that are being built sometime very soon.

With the price being right, I put an offer in and it was accepted.  Given the proximity of the seller, I received the preamplifier the next day.  Unpacking the Classe Five and I found myself with a very heavy duty unit that was nearly flawless.  The switches, which have a wonderful tactile feel, worked perfectly, as did the remote control and the various knobs.  The wireless remote has buttons that causes little motors on the volume and balance to physically turn the knobs.  Very neat (I'm still an adolescent at heart!).  This is also great for adjusting the gain to get that perfect playback level from the comfort of my favorite listening chair.

Initial Impressions:
It is always exciting to listen to something new - but the Five wasn't exactly earth shattering.  The sound was dark, a bit muffled, and seemingly missing some bite on the top end.  Bass, however, was controlled and the overall sound was smooth.  With only an hour or so of time, I went to bed, leaving my new preamplifier in standby mode since there is no power off button.

The next day, after work, I heard an improvement in sound.  The smoothness was still there but everything sounded a lot more cohesive.  I fought the urge to do any serious listening, waiting for a quiet Sunday afternoon where I could experience the Classe Five without any familial distractions.



In my doddering middle-age I've become a bit of a Chet Baker fanatic, even exploring his musical output beyond his 1950s heyday.  Nonetheless I still have an appreciation for his signature album, Chet.  It's a brooding masterpiece that has the fingerprints of Bill Evans all over it.  Listening to this album - 1980s Riverside pressing - reveals a lot more detail than I was hearing through the Adcom GFP-555.  The Classe Five does a better job of revealing the light cymbal work, which sounds deeper in the soundstage but with the attack and decay being more apparent as is the metallic nature.  Too many systems turn cymbals into a hard SHHHH noise, instead of the shimmering, complex sound it should be.

Instrument - piano, the brass instruments, and drum - have a more natural body than my old preamplifier.  The overall sound is very smooth but doesn't inhibit the more aggressive tones of the music.  It is a different type of smoothness than I ever heard; not imbued with a golden hue like a vintage tube preamplifier but more as if the sonics were cut from a single, grain-less cloth. 

Willie Nelson has a rich and immediately familiar voice.  On Stardust, the vocals come across as completely natural with just a hint of studio reverb added.  The instruments remain firmly behind the singer, reproducing the very intimate nature of this album.  Tonality is some of the best I heard, exceeding my expectations given the budget nature of the speakers and my turntable and cartridge. Cohesiveness is another word that came to mind, and one that kept popping up as made notes.  No single instrument seemed crowded out while another took the center of attention.



For something more dynamic, I turned to one of the greatest live blues albums ever recorded: Drinkin' TNT 'n' Smokin' Dynamite which has an all star backing band behind Buddy Guy and Junior Wells.  The Classe Five captured the audience background noises allowing me to place them in location and distance from the stage.  The dynamic shifts, given the limitations of the Wharfedale Denton speakers, were impressive; never sounding bloated or blurred.  An example of this is the stuttering starts and stops of the lead guitar, along with the deep bass foundation.  Each instrument had its own space but jelled together as one whole, making for a very toe-tappin' experience.


After that good time, I needed a melancholic change of pace.  Richard and Linda Thompson deliver this in spades with their album Shoot Out the Lights.  Linda's voice is sublime here, all barely hidden pain while the barbed wire guitar of Richard grinds away as if stripping the heart out of his troubled marriage.  His backing vocals sit separate from hers, as if he is giving his ghostly agreement.  This album, needless to say, a heart-wrenching series of songs.  The Classe Five does an excellent job of baring these emotions.





I listened to several other albums of varying quality - like The Fixx, Wardruna, The Police, and even some old 1930s-era Billie Holiday.  Poor recordings sounded like, well, poor recordings.  And mediocre ones weren't given any extra magic either.  The Classe Five appears to be rather neutral, low in coloration, and even-handed.  This one is a keeper.


Takeaways:

The Classe Five has the best treble I have ever heard from a solid-state preamplifier.  At first I thought it was rolled-off; lacking in air and excitement.  However further listen revealed that it is actually a lack of glare and edginess that is often common in lesser solid-state gear.  If a recording is bright, you will hear that.  If it is dull, or poorly recorded, that will be revealed.  There is no heavy coloration going on here.

Along with this natural treble comes the feeling, from top to bottom, that all frequency points are sonically similar; that is to say no part of the sound, be it treble or bass, sticks outs or draws attention to itself.  As I mentioned above, everything is cut from the same sonic cloth.  It's something I never quite heard to this degree with any preamplifier that I've ever owned and took some time to understand this new experience.  A similar situation occurred when I first heard the VPI Aries 1, only then did I hear the warble and background rush of lesser turntables.

Bass control is excellent - tight and dynamic without any bloat or smear.  This is essential for providing the foundation of the song.

Detail is very good; though some listeners may prefer a more hyper detailed presentation.  Perhaps this is the limitation of my front-end or the nature of the Wharfedale speakers.  Some future upgrades will see how well this holds true.

The quality of the Classe Five makes me question, to some degree, my allegiance to valves.  At least with valve gear you can roll in different tubes to find the best match with your system.  But, if you're tired of buying high priced NOS valves or even new stock, then give the Classe Five a try. You may be surprised.


System:
Adcom GFA-545 amplifier
Dual CS5000 turntable with Ortofon OM20 phono cartridge
Pioneer DVD-V7400 DVD player
Kimber 8PR/4PR bi-wire speaker cables
various budget interconnect cables

Short Take: the Adcom 545

(picture from Google Images)

My old McIntosh MC2100 is in desperate need of a rebuild.  This poor amplifier, after all, is knocking on forty or more years of usage, which means capacitors, resistors, and other bits are due for replacement.  This age has shown up as "vintage" warmth, but also a rolled-off top, plummy bass, and some signal degradation.  To put it bluntly, this amp sounds old and tired.

With that in mind I decided to replace the Mac with a partner to the Adcom GFP-555, the venerable GFA-545.  Of course the 545 is no youngster either, but it is inexpensive and can also be stacked on top of the preamplifier.  Given my tight listening space this was the biggest reason to go this route.

The Adcom GFP-545 is a conservatively rated 2-channel power amplifier making 100WPC.  5-way binding posts, RCA inputs, captive power cord, etc.  Very basic and no frills with only the mentioned connections, an on-off switch and indicators if either channel is clipping.  Designed by Nelson Pass, it sits between two other models, the 60WPC GFA-535 and the 200WPC GFA-545.

In the 80s and even up to the 90s, Adcom amplifiers were mainstays in many, many systems,  My father still has an original 555 running in his downstairs home theater system, so that speaks of some good reliability.  But, like my McIntosh 2100, they are getting to the point where some maintenance is due.

How does it sound?  At least in my budget system, very good.  With the fresh power supply and direct coupling, the Adcom had much better and tighter bass than the McIntosh.  It does lack some of the warmth, but the clarity and detail is higher along with a less grainy presentation.  Top end is extended, perhaps a little etchy compared to the best tube amps, but nothing that will drive the listener out of the room.  So a good basic power amp that can be used in a variety of systems.

Ultimate fidelity?  In a word: no.  But my current system is a whole bunch of compromise, and with the soft presentation of the Shure M97xe / Dual CS5000 combination and the nature of the Adcom GFP-555 preamplifier, it somehow all works, even blunting the forward character of the B&W 805s,

So for now the Adcom 545 delivers music and does it in a way that I find inoffensive.  But with tube amps coming soon it's time in my system is short.

Review: McIntosh MC2100 power amplifier

It was vintage McIntosh tube gear that launched my interest in high-end audio which is a bit funny since - and I'll be sure to get some flack for this - these older preamplifiers and amps aren't necessarily the greatest in the world.  But I will give them credit for making a piece of gear that is certainly memorable; the lit glass fronts and layouts are visually striking while the sound coming out of the speakers is warm and robust.

As I already mentioned in the previous post, I've sold off my previous system, retaining only the UREI 813A loudspeakers - for now.  Part of this was due to the location of the system - the dark basement isn't exactly my favorite place to hang out - and the realization that I was spending thousands of dollars on something that was only being used a few hours a month.  So with that in mind, I decided to simplify; concentrating on the musical aspects of reproduction instead of the ultimate fidelity.  Since the B&W 805 speakers like power I thought it best to replace the Nakimichi receiver in my upstairs system with something with a little more drive.

I remembered how much I liked my departed McIntosh MC-250.  I also noticed that prices are rising on these vintage amplifiers.  But my luck held out and I managed to find the 250's big brother, the heavy-duty MC2100 for only six hundred dollars.  It has twice the power and the same utilitarian (some might say industrial) look of its smaller sibling.  When funds permit, I may go for a matching McIntosh preamplifier - though of a later vintage - and tuner, but for now I've gone the budget route with a first-generation Adcom GFP-555.

The McIntosh MC2100 is rated - very conservatively - at 105WPC and features autoformers on the output.  It can, at least according to various sources, easily exceed that value.  And after hooking it up to my B&W Matrix 805 speakers, the first thing that I noticed was more bass oomph and dynamic drive.  The little 5" woofer of 805s don't exactly move a lot of air, so this was a pleasant surprise over the Nak receiver.  Perhaps it is the nature of having an autoformer on the transistor output stage, but this bass had a slight (and I mean very, very small) loosey-goosey nature.  It wasn't sloppy, but was just a touch less tight and less sterile than the Japanese receiver.  In my book that's a good thing.

With these early SS pieced of McIntosh there have been many comparisons to tubes.  The midrange, with well-recorded pieces like Steve Forbert's Jackrabbit Slim, or Gary Numan's Splinter had a warm character, but lacked that ultimate finesse and clarity that the best tube amplifiers have.  Instead I'm vaguely reminded of the venerable B&K ST-140, which has a (non-linear?) dc-blocking electrolytic capacitor on the input stage.  It adds some "FM Radio" character that is pleasant and conducive to long-term listening but should not be mistaken for uber-fidelity.  Of course that's not what I'm striving for here so there are no disappointments in this area, but just something to be noted for any readers looking for the "ultimate" amplifier.

It is the upper-mids and treble where most solid-state amps fall on their face.  I would give the McIntosh MC2100 a high passing grade here.  It suffers from the sins of omission, clouding some detail and rolling off the treble.  Again we are talking about musicality over the ultimate extension and pin-point imaging.  A rough analog: perhaps the MC2100 is closer to a good moving magnet instead of a hyper-detailed moving-coil cartridge.  As a side note: when I had a MC250 around, I noticed some grain in the texture, but, at least with this current setup, I'm not hearing that same kind of effect

Imaging and depth are good but not superlative.  Of course some of this is the fault of my speaker setup, the limitations of the Dual CS5000 turntable and Nagaoka MP-110, and perhaps the use of an Adcom preamplifier, which isn't exactly the best in the world.  Future upgrades will give a clearer picture of the limitations of this amplifier.

At least to my ears, the McIntosh MC2100 is a fine solid-state piece of gear if - and this is an important point - one is not reaching for the ultimate fidelity, but instead prefers emotion.  It is here where this amplifier shines, being a sort of "poor man's tube amp."   No, it doesn't sound like a Dynaco 70 or even come close to my departed Eico HF-60s, but it does capture the essence of the musical performance and minimizes the worst aspects of a budget system.  So in that regard, the McIntosh MC2100 is a clear winner.

System:

Dual CS5000 turntable with Nagaoka MP-110

Pioneer DVD-V7400

Adcom GFP-555

B&W Matrix 805s on stands

Wire: Various brands

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

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.

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.

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 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.

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