Review: Sovtek 12AX7WA

 I have a love and hate relationship with Russian tubes.  Some of them - like the ECC99 - rival some of the best vintage American and European tubes, while others, like much of the Electro-Harmonix line sounds like solid-state in a bottle.  Yes these tubes can be transparent but they are often lacking in detail or suffer from an aggressive treble and upper midrange.

The early Russian tubes, that first were available in the 1990s to the Western World, were godsend to the tube-o-phile community.  They were cheap and rugged.  An example of this is the 5881WXT which could take the current hungry bias of the Harmon-Kardon Citation V.  Even a RCA blackplate of the era would start to glow on the seams.  But not these Russian mil-spec tubes.

It's been my belief - shared by some friends too - that Russian tubes have good metallurgy but not the best cathode chemistry.  Yes they are rugged, but many of them have the already mentioned issues with the higher frequencies.

As for the Sovtek 12AX7WA, it has a pair of very small coated plates and what I would call a primitive looking spacer that should be made out of mica.  The pins ends are sharp but overall construction looks quite good.  I plugged it into my Frankenstein EICO ST70, which provides the initial gain before the 6SN7 phase-splitter.

The Sound:  Initially I was surprised how much I like the Sovtek.  The sound was very transparent and, at first listen, very modern sounding.  I was reminded of a really good JFET preamplifier or MOSFET amplifier - big, dynamic and smooth.  But, like the aforementioned solid-state gear, lacking in inner detail.  The soundstage was also smeared a bit, removing the space around individual instruments and the big front-to-back sound of a vintage Mullard.  Dynamics in the upper part of the spectrum became a little rough/forced sounding with the Sovtek.

What I'm really finding - at least so far - is that modern tubes often has a good tonal presentation but lack in inner detail and making a big soundstage.  I'm curious to the reason why this is true.  Is this linearity or an artificial presentation brought on by - an unknown variable?  We shall have to continue and have some vintage comparisons.  More later!

Review: Psvane 12AX7

 

The Psvane T-12AX7, apparently the base version, is a Chinese design that looks much like a vintage one with gray ribbed plates, quality construction, and steel pins.  The triple-layed mica also looks good.  Bulb size, like so many other new tubes, is slightly larger than my collection of old stock, a mm or two difference in height and circumference..

Break-in was approximately fifty hours as the driver tube in my Frankenstein Eico ST70.  This is basically the classic Mullard 5-20 circuit.  It's been my general experience that the driver tube - before the phase splitter - has a high impact on the overall amplifier sound, more so than the phase-splitter or even the output tubes.

Listening was initially done while reading a book.  There were several times where I had to look up from the pages to truly appreciate what I was hearing.  Like the TJ FullMusic, the Psvane has a great almost vintage tone.  I was hearing little details - an example is Lonnie Liston Smith's Vision of a New World - that I thought weren't apparent to my standard vintage Mullard.  I was beginning to feel some really high hopes for this Psvane.

However some further, more detailed listening, some of it shared with an old audiophile friend with an extensive knowledge of 12AX7s both new and old, began to show some weaknesses.  Though the sound was never muffled, the Psvane, like the TJ, also lacked inner detail and bloom around the instruments.  But wait a minute, you say, where did that extra detail you mentioned go?  It is a strange effect of the Psvane: suppression of reverberation both artificial or natural, pushed some information forward.

Keep in mind this is still the best new production 12AX7 I've heard and I could see use for it in gear or speakers that aren't the most transparent.  The bass was excellent, there was a distinct lack of glare unlike some lesser "solid-state in a bottle" new production tubes.  The midrange was also even as was the treble.  It was just the lack of detail that stopped the Pvane running with the best of the vintage 12AX7s.

Disclaimers: No tube is 100% perfect for all gear.  The only way to be sure how a tube will sound in _your_ system is to hear it.  Also a tube in a phono stage, for example, may have different audio characteristics than say line, input, or phase-splitter use.

 Negative feedback - several dB in this circuit - also reduces the sonic signature of the tube.  An example of this came apparent to me when I built a triode-connected EF86 linestage.  The tube selection - GEC CV4085 and the Mullard "long mesh" were the best - played a big role in the sound quality.  However the EF86 in my Eico HF60 monoblocks were less important, most likely due to the loop negative feedback or perhaps the total number of tubes in play with a more complicated circuit.

 It should also be noted that I am not biased towards vintage tubes.  I really do want a new tube that can compete with the old.

So take this review as a general guideline, not as hard fact.

Review: TJ FullMusic 12AX7

 

 

The TJ Full Music 12AX7 is a box plate Chinese design that looks much like a vintage Mullard M8137 and completely unlike any other current new 12AX7 offering.  The gold pins are a nice touch, and it looks like actual mica (?) was used instead of the whatever the heck is used for the Shuguang small tubes.  Bulb size is slightly larger than my collection of old stock, a few mm difference in height and circumference..

Break-in was approximately fifty hours as the driver tube in my Frankenstein Eico ST70.  This is basically the classic Mullard 5-20 circuit.  It's been my experience that the driver tube - before the phase splitter - has a high impact on the overall amplifier sound, more so than the phase-splitter or even the output tubes.   

Tonally the TJ 12AX7 was one of the better new production tubes I've heard so far.  I was initially hard-pressed to hear any difference between it and a quality old tube like a 1950s Mullard.  Bass definition and instrumental shading of the TJ was particularly good, but, even as the hours piled on, I detected a slight muffled sound.  There was a lack - especially compared to the Mullard - of inner detail or instrumental/vocal bloom.  That is to say the TJ had a flatter and smaller presentation.  I'm reminded of an inexpensive cartridge or CD player; the magic "glow" or shimmer, whatever one prefers to call it, was pulled back on the soundstage.

The old Mullard, in comparison, sounded bigger and had better bloom.  The music was more "filled in" with depth and soundstage width.

Do the TJs need more break-in?  I really didn't hear large differences between hour zero and fifty so I remain skeptical.  Nonetheless I did like the TJ tonally, especially compared to some other new production valves I have heard, but I was ultimately disappointed.  I do want new tubes that can perform in the realm of the best of the old.  At least with this tube I'm not hearing it!

Disclaimers: No tube is 100% perfect for all gear.  The only way to be sure how a tube will sound in _your_ system is to hear it.  Also a tube in a phono stage, for example, may have different audio characteristics than say line, input, or phase-splitter use.

 Negative feedback - several dB in this circuit - also reduces the sonic signature of the tube.  An example of this came apparent to me when I built a triode-connected EF86 linestage.  The tube selection - GEC CV4085 and the Mullard "long mesh" were the best - played a big role in the sound quality.  However the EF86 in my Eico HF60 monoblocks were less important, most likely due to the loop negative feedback or perhaps the total number of tubes in play with a more complicated circuit.

So take this review as a general guideline, not as hard fact.

Tube Review: Genalex - Gold Lion B759 / 12AX7A

(Image from Google)

I'll admit right off the bat that I've never been a huge fan of small signal Russian tubes.  Overall they seem to have a "solid-state in a bottle" effect and certainly don't come close to some of the better NOS offerings from Mullard, Amperex, RCA, and company.  I would even prefer to spend my money on GE, Ei, Raytheons, or CBS tubes.

The other night I was given a chance to borrow a pair of re-issue Genalex B759 / 12AX7A tubes.  The boxes are certainly a nice copy of the original, as is the logo imprinted on the glass.  However, if you compare the "re-issue" to the original, they are in fact nothing alike.  Of course the machinery that made the original British tube is long gone.  It's a small point, but I never liked the use of the term "re-issue" which means, at least to me, that the product actually has some connection to the past.

Instead, the Genalex B759 looks like a Sovtek 12AX7LPS - the plate, mica, and layout are the same.  Perhaps there is some magic going on with the screens and cathode chemistry, but that's difficult to tell without breaking them and taking a look inside while doing a chemical analysis.  So one theory - these could be just highly selected and matched "super" Sovtek tubes.  Perhaps a softer vacuum could come into play.

Okay, enough intellectual yammering.  How does the tube sound?

My Quicksilver full-function uses a 12AX7 as the first tube in the phono section.  The linestage also has one.  I pulled out my 1960s short-plate Mullards and replaced them with the Genalex B759.  I had a fellow audiophile over to listen.  As we talk tubes and single-ended amps, we let the whole system warm up for a while before listening.  Hmm... this actually sounds better than I expected.  Yes, the Genalex tubes do sound different than the Mullards, but within the confines of this system, the B759s are completely acceptable.

The first word that comes to mind is fast - perhaps due to a bit of additional upper-midrange/lower-treble excitement.  This extra bit of zing makes music fun and engaging, all without sounding overly bright or with the type of "solid-state" grain I normally associate with many small signal Russian tubes.  Overall depth seemed a tad flatter than the Mullards, but the effect lessened the longer the preamplifier was on.  Coherency from the lowest to the highest octave was even handed, except for the already noted touch of forwardness.  "I could live with these" was one comment I made as Fleetwood Mac was spinning away.

So yes, the Genalex B759 / 12AX7A does deliver the goods, though I fear a more revealing speaker - like the UREI 813As - would show more limitations.  I suspect this tube may not be a good match for forward systems - especially ones using horn loudspeakers.  However, they would be a great match for some darker sounding gear like the Dynaco PAS or Eico HF-85 preamplifiers.  With the ever rising cost and increasing scarcity of decent NOS tubes, it is good to know that there are real alternatives out there.

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.