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VTA ST-70 Review (Stereo Tube Amplifier)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 123 64.7%
  • 2. Not terrible (postman panther)

    Votes: 45 23.7%
  • 3. Fine (happy panther)

    Votes: 16 8.4%
  • 4. Great (golfing panther)

    Votes: 6 3.2%

  • Total voters
    190

rebbiputzmaker

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In the same way that a doctor expresses his opinion of my overall health based on a bunch of objective measurements and tests, I have no problem with a knowledgeable, experienced electrical engineer expressing his opinions based on what he finds after an examination of a box of electronics. That doesn't mean that my doctor can't be wrong, nor does it mean our host is infallible, but it does mean he starts with a level of credibility that few reviewers have, and to say he should just be a measurement bot is a bit silly.

I do understand that a lot of people don't like it when their special gear is made out to be less special than they believe it should be.
You don’t get it. :) That amp happens to be relatively crappy but that does not mean that all tube equipment is and if applied properly can be fine. Possibly not the best idea to discuss medicine in this context because you would want your doctor to have extensive knowledge and experience, not just post 1970 and maybe not have skipped Grey’s Anatomy.
 

SIY

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You don’t get it. :) That amp happens to be relatively crappy but that does not mean that all tube equipment is and if applied properly can be fine. Possibly not the best idea to discuss medicine in this context because you would want your doctor to have extensive knowledge and experience, not just post 1970 and maybe not have skipped Grey’s Anatomy.
I missed the post where BDWoody said that all tube amps are crappy.
 

BDWoody

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That amp happens to be relatively crappy but that does not mean that all tube equipment is and if applied properly can be fine.

Where does he say otherwise?

What I saw was the same crap amp that you did, called out with pretty rough measurements.

Other than the unique look of the unit, I am the wrong guy to ask about the appeal of these tube amps.

Is that a condemnation of all tube amps?

What am I not getting, other than some people like it, and feel the need to disparage the review/reviewer when his measurements and conclusions paint it in a negative light...which they do. It didn't even get a headless panther, in casual recognition of its non-standard place in the amp world.
 

FrantzM

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I missed the post where BDWoody said that all tube amps are crappy.
Same here.
...
...
But anyone who would have said that, would not be too far from the truth :p ...
And this is me dodging the bullets :
51b8dcc8afd03195ccd9a548273e5963.jpg

:D
 

captainbeefheart

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Hello to everyone, I really enjoy Amir's reviews and appreciate everything he does for the community.

My concerns are that why people make such blanket statements about active devices, certainly most of us should know by now that with enough open loop gain we can achieve fantastic numbers regardless of type of active components. The problem with tube amps is the output transformer typically limits us to <30db of negative feedback which if you take enough care to make the open loop circuit linear enough should be plenty to get very low distortion.

I have looked but I haven't seen one well designed tube amp reviewed here, I think that needs to change in order to show good performance can be had with tubes. For example the original Mullard circuit can get 20 watts output with .05% THD. This is original circuit with zero help from many decades of experience. For example do you see many transistor amps that use resistive loads? No, they use high AC impedance loads like current sources, so load tubes with appropriate high impedance loads and you'll notice a substantial decrease in distortion. Part of the issue I believe is many of the tube companies don't want to spend the time to work out the compensation networks, I test so many tube maps with awful ringing that can be fixed with some simple control theory application.

So how is it here we are in 2022 and tube amp manufacturers are still just copying resistor loaded circuits from the 40's and 50's? I have been lately researching the David Berning circuit for his bridged output impedance converter which removes the worst part about the tube circuit, the output transformer. We still use TWT in space communications so tubes are still top dog in many applications. I'd love to give Amir some amps I have made as they perform FAR better than the majority on the market because I don't copy old designs and I'm just a nobody with a desire to use tubes for no apparent reason other than I like them. I am not saying tubes are better or worse, everything has it's pros/cons but I admit I just use tubes because I find them funner to build with and nothing else. I find it odd a nobody like me with little effort can get much better specs than these amps selling for thousands of dollars where I on average spend $500 for my builds. Must be a pretty huge markup with some of these awful amps on the market giving tubes a bad name.

I eagerly await Amir to get a decent tube amp to measure to put the whole "tubes make distortion" myth to rest, to me it's more tube makers are afraid of feedback for some reason and that's the downfall not the fact they use tubes.
 

captainbeefheart

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To Amir,
I really enjoy your tests but would really like to see some additional tests added. One would be testing with reactive loads to see what's really going on, I have seen far too many amplifiers with marginal phase margin and when loaded with a little capacitance break into ringing and overshoot. So maybe some square wave tests added to amplifiers testing would be great to see a "bigger picture", I feel fatigue is often related to ringing and overshoot with treble frequencies.

One more suggestion, I use null tests a lot in my day job and they can produce very fast answers to the ultimate question "is one thing not like the other things". A quick null test should show any differences between two things very clearly.


That's all, keep up the great work I love this place!!
 

ta240

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...
I admit that for me, as a hobbyist, it doesn't really matter. For ASR, however, the idea (as I understand it) is to decide the best engineering given what is out there, and given what one has to work with. But there has to be some grounding. Some overriding perspective to it.
....
I think it is more about trying to prove 'the other side' wrong in the ongoing debate rather than locating the best engineered audio examples and highlighting them; otherwise, as you point out they would just ignore some types of equipment. There is no possibility that anyone on here thought this amp would outperform, technically, the modern amps tested.

It is more of a "You should not like your steak medium, you should like it rare and here is why!" type argument. Or often it is "How dare you say your medium steak is tastier than my rare one!!!!".....
Second, measurements need to evolve to measure some of the immersive qualities. I don’t know how this needs to be done but it does. Audio science should work towards utility that is both technically good and practically good. For an example, right now the Aiyima A07 is unbelievable value, and blows the VTA70 out of the water on theses test. However, as an owner of both they are no where in the same league, and I can’t imagine anyone picking the Aiyima over the VTA, blind.....
But that would require the double blind testing that is yelled at anyone that ever says they liked the sound of a product that doesn't measure well; yet is never done to see if the fans of precision really can hear a difference themselves of the better measuring product.
 

ta240

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We are not in "perhaps" business. Tubes create distortion. That distortion is frequently inaudible to typical audiophile who is not trained to hear them. So what they observe is made up based on improper listening tests and believing in audiophile myths. As I observed in my video review, all I hear is distortion and degradation here as I turned up the volume. There is no "greater sense of realism/presence."

I guess I missed the double blind test.

No other person on here would ever get away with saying they heard something that a salesperson told them would be there in a sighted test. They would be mocked and chased away.
 

SIY

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Hello to everyone, I really enjoy Amir's reviews and appreciate everything he does for the community.

My concerns are that why people make such blanket statements about active devices, certainly most of us should know by now that with enough open loop gain we can achieve fantastic numbers regardless of type of active components. The problem with tube amps is the output transformer typically limits us to <30db of negative feedback which if you take enough care to make the open loop circuit linear enough should be plenty to get very low distortion.

I have looked but I haven't seen one well designed tube amp reviewed here, I think that needs to change in order to show good performance can be had with tubes. For example the original Mullard circuit can get 20 watts output with .05% THD. This is original circuit with zero help from many decades of experience. For example do you see many transistor amps that use resistive loads? No, they use high AC impedance loads like current sources, so load tubes with appropriate high impedance loads and you'll notice a substantial decrease in distortion. Part of the issue I believe is many of the tube companies don't want to spend the time to work out the compensation networks, I test so many tube maps with awful ringing that can be fixed with some simple control theory application.

So how is it here we are in 2022 and tube amp manufacturers are still just copying resistor loaded circuits from the 40's and 50's? I have been lately researching the David Berning circuit for his bridged output impedance converter which removes the worst part about the tube circuit, the output transformer. We still use TWT in space communications so tubes are still top dog in many applications. I'd love to give Amir some amps I have made as they perform FAR better than the majority on the market because I don't copy old designs and I'm just a nobody with a desire to use tubes for no apparent reason other than I like them. I am not saying tubes are better or worse, everything has it's pros/cons but I admit I just use tubes because I find them funner to build with and nothing else. I find it odd a nobody like me with little effort can get much better specs than these amps selling for thousands of dollars where I on average spend $500 for my builds. Must be a pretty huge markup with some of these awful amps on the market giving tubes a bad name.

I eagerly await Amir to get a decent tube amp to measure to put the whole "tubes make distortion" myth to rest, to me it's more tube makers are afraid of feedback for some reason and that's the downfall not the fact they use tubes.
Howdy, Cap’n! Berning has long been one of the few guys doing actually new and creative things with tube amps. The results have been a mixed bag, but they do several things very well. Tim deParavicini also did some really nice work. Past that… well… there’s some good diy efforts but commercial contemporary tube amps are depressing reworks of 70 year old designs, and done less well.
 

captainbeefheart

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Howdy, Cap’n! Berning has long been one of the few guys doing actually new and creative things with tube amps. The results have been a mixed bag, but they do several things very well. Tim deParavicini also did some really nice work. Past that… well… there’s some good diy efforts but commercial contemporary tube amps are depressing reworks of 70 year old designs, and done less well.
Hello SIY, I agree the Berning circuit isn't the silver bullet but I find it refreshing that someone took relatively old technology by today's standards and got rid of the output transformer. I do find your statement about commercial tube amps being for the most part a regression rather than a progression spot on. I half think it's intentional, they know they need their amps to stand out against the crowds so what better way to get it then output transformer saturation for large 2H distortion at low frequencies, hello free bass information and also the high output impedance gives the boomy one note bass at resonance. Think the Crimson 275 debacle, people reviewed it as having thundering bass etc.. Some members in my other audio groups also noted how "full" the bass was. The defacto "tube amp" has become a smoke and mirror effects box to add to the analog information embedded into the original content creating new information content (distortion) misconstrued by the untrained ear as an improvement. I guess who are we to judge if someone prefers inaccuracy? If it sounds "good" to you and you enjoy it then that is the point to why we listen to music anyway right? At the very least call a spade a spade and say "Hello my name is Captainbeefheart and I like distortion". We aren't reading an MRI or mapping the stars so I find even if the market wants regressed circuits then it says something about us as a species.

I'm still working out how people think they can trust their senses. Perception is a construct by our own invention and we never passively process the physical world around us so how can we ever trust our own judgement when swapping cables without doing a blind test but somehow this is highly argued also along with capacitors, tubes vs transistors, etc.... Ahh the fun of audio forums and the same old conversations going round and round in circles.
 

SIY

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I'm still working out how people think they can trust their senses. Perception is a construct by our own invention and we never passively process the physical world around us so how can we ever trust our own judgement when swapping cables without doing a blind test but somehow this is highly argued also along with capacitors, tubes vs transistors, etc.... Ahh the fun of audio forums and the same old conversations going round and round in circles.
I love the irony of "trust your ears!" being used as a mantra for "You have to peek."
 

rebbiputzmaker

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Hello to everyone, I really enjoy Amir's reviews and appreciate everything he does for the community.

My concerns are that why people make such blanket statements about active devices, certainly most of us should know by now that with enough open loop gain we can achieve fantastic numbers regardless of type of active components. The problem with tube amps is the output transformer typically limits us to <30db of negative feedback which if you take enough care to make the open loop circuit linear enough should be plenty to get very low distortion.

I have looked but I haven't seen one well designed tube amp reviewed here, I think that needs to change in order to show good performance can be had with tubes. For example the original Mullard circuit can get 20 watts output with .05% THD. This is original circuit with zero help from many decades of experience. For example do you see many transistor amps that use resistive loads? No, they use high AC impedance loads like current sources, so load tubes with appropriate high impedance loads and you'll notice a substantial decrease in distortion. Part of the issue I believe is many of the tube companies don't want to spend the time to work out the compensation networks, I test so many tube maps with awful ringing that can be fixed with some simple control theory application.

So how is it here we are in 2022 and tube amp manufacturers are still just copying resistor loaded circuits from the 40's and 50's? I have been lately researching the David Berning circuit for his bridged output impedance converter which removes the worst part about the tube circuit, the output transformer. We still use TWT in space communications so tubes are still top dog in many applications. I'd love to give Amir some amps I have made as they perform FAR better than the majority on the market because I don't copy old designs and I'm just a nobody with a desire to use tubes for no apparent reason other than I like them. I am not saying tubes are better or worse, everything has it's pros/cons but I admit I just use tubes because I find them funner to build with and nothing else. I find it odd a nobody like me with little effort can get much better specs than these amps selling for thousands of dollars where I on average spend $500 for my builds. Must be a pretty huge markup with some of these awful amps on the market giving tubes a bad name.

I eagerly await Amir to get a decent tube amp to measure to put the whole "tubes make distortion" myth to rest, to me it's more tube makers are afraid of feedback for some reason and that's the downfall not the fact they use tubes.
Good luck you’re gonna need it.

Remember tubes cause distortion.

I told this to my WE 437s and they have not been the same since. :confused:
 

captainbeefheart

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I told this to my WE 437s and they have not been the same since.

Tubedepot is asking $1295.00 for one of them these dayso_O

I sell off any tube that has a ridiculous market value because I cannot justify the use in an application where a $5 tube will do the same thing.

I'd wager a bet that the 4P1L in triode mode is more linear than a WE 437a. I have over 50 "Winged C" Military surplus cream of the crop versions I paid $2 each for:D
 

JP

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vkhong

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I'd love to give Amir some amps I have made as they perform FAR better than the majority on the market because I don't copy old designs and I'm just a nobody with a desire to use tubes for no apparent reason other than I like them.

@captainbeefheart Can you share more information about the amplifiers you build? If there is sufficient interest from the members, I think @amirm could be persuaded to test your amplifier.
 

rebbiputzmaker

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Oh man. I sold a little more than a dozen of those a decade ago for far less.
I sold mine also when they were less. I’d be surprised really if many people are paying that much money. The Russian alternative 6c45pi is also very good.
 

rebbiputzmaker

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Tubedepot is asking $1295.00 for one of them these dayso_O

I sell off any tube that has a ridiculous market value because I cannot justify the use in an application where a $5 tube will do the same thing.

I'd wager a bet that the 4P1L in triode mode is more linear than a WE 437a. I have over 50 "Winged C" Military surplus cream of the crop versions I paid $2 each for:D
Tubes can be a beautiful thing but many would rather stick to the party line.
 

Vortex

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Talking about the Dynaco and tube amp optics... wouldn't you own one of these ? :)
I think if there's something like tube amplifier porn, this is it.
 

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Jim Taylor

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Talking about the Dynaco and tube amp optics... wouldn't you own one of these ?

As you say, the optics (appearance) reign. The performance under load, however, isn't so good:

THe Jadis Orchestra Black, as measured by Stereophile:
320JadisOBfig01.jpg

The Jadis Orchestra Reference:
1215Jorchfig1.jpg

And the Jadis I-35, with slightly better specs under load:
114JI35fig01.jpg

... but I.M. measurement that's .... (ahem!) .... not very good:
114JI35fig11.jpg

Remember: looks aren't everything. :) Jim
 
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