VTA ST-70 Review (Stereo Tube Amplifier)

[pseudoid]

The vote is membership reflection of the data as presented, plus anything else they would consider (e.g. cost).

Like a collective FWIW... it also allows us engagement. Thank you @amirm!

 

[anmpr1]

Why couldn't you pick the Vette or the Porsche for your comparison...

Well... only because the Golf is more or less an evolved Beetle.

On the other hand, I'm sure we can find someone piloting an air-cooled rear engine Beetle who imagines that he's not so far removed from a '93 911. But, then again, there is always someone claiming to be related to the Romanov's, yet once they do the blood test it never pans out. And in spite of the stretch, for sure an authentic Beetle is closer in DNA to a 911, than a fake Anastasia is to the deposed royal family.

Funny thing about Dyna... everyone and their brother wanted a piece of the action. Bill Johnson of ARC sold ST-70 mods. Before that, Gene Coggins ran an operation called Paoli Hi Fi Consultants, whose Dyna (Mk III--see below) mod was Gordon Holt's beez kneez, for a while, and in the early 'you never knew when you were going to get it' days of Stereophile. We can't forget Frank van Alstine, at Jensen's Stereo Shop, who was modding Dynaco gear even before David Hafler met Ed Laurent!

I recall reading (or maybe I just made it up) about someone asking Dave Hafler his opinion of the mods. His was something to the effect that he didn't care, because a sell was a sell, and once modded he didn't have to worry about warranty problems!

 

[B&WTube]

Step 1: Confirm via ears-only tests that these aspects actually audibly exist. Then measurement becomes straightforward.

I can’t imagine anyone who experienced a lot of good gear, of all flavors, disputes this- it’s just not stuff we don’t know how to measure.
For example depth of soundstage are obviously very real, but no one knows how to measure it.
Perhaps the tubes have a pleasing second order harmonics that people like and creates a greater sense of realism/presence. Perhaps there are tiny higher order harmonics in the Aiyima that make it slightly harsh on some notes. I really don’t know the answer- but it is clear that it is a thing.
The cliches in subjective listening are cliches for the same reason as every other cliche- there’s an element of truth to them. I would just like someone smarter than I am to work out what it is, and then we can measure it.
So I am very much for measurements, because I am for more measurements. This particular amp is an incredible value in the tube world, and it is loved over far better measuring gear- It would be good to understand why.

 

[SIY]

I can’t imagine anyone who experienced a lot of good gear, of all flavors, disputes this- it’s just not stuff we don’t know how to measure.
For example depth of soundstage are obviously very real, but no one knows how to measure it.
Perhaps the tubes have a pleasing second order harmonics that people like and creates a greater sense of realism/presence. Perhaps there are tiny higher order harmonics in the Aiyima that make it slightly harsh on some notes. I really don’t know the answer- but it is clear that it is a thing.
The cliches in subjective listening are cliches for the same reason as every other cliche- there’s an element of truth to them. I would just like someone smarter than I am to work out what it is, and then we can measure it.
So I am very much for measurements, because I am for more measurements. This particular amp is an incredible value in the tube world, and it is loved over far better measuring gear- It would be good to understand why.

Evidence is far better than handwaving.

 

[amirm]

For example depth of soundstage are obviously very real, but no one knows how to measure it.

We can't measure what is not real. The only way an amp can change the spatial effects is if it has non-flat response in the 1 to 3 kHz region which would be horrible design (but can happen due to high impedance). Outside of that, imaging effects are made up by people in evaluation of audio systems so there is nothing to measure. Look to the content for where these effects are created and to some extent, your speaker and positioning of them in the room.

 

[amirm]

Perhaps the tubes have a pleasing second order harmonics that people like and creates a greater sense of realism/presence.

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."

 

[pseudoid]

That distortion is frequently inaudible to typical audiophile who is not trained to hear them.

Having been married to a McIntosh MC275 for 25 years must make me unqualified for both being an audiophile or a golden-ear.
bum!

 

[MidnightCarouselRider]

I have 2 amps. An Aiyima A07 and a Bob Latino ST120. They both sound great. It blows my mind the A07 was 70 bucks. But...I can listen to the ST120 louder and for longer periods. How do you measure that?

 

[amirm]

I have 2 amps. An Aiyima A07 and a Bob Latino ST120. They both sound great. It blows my mind the A07 was 70 bucks. But...I can listen to the ST120 louder and for longer periods. How do you measure that?

We would measure the frequency response coming out of the speaker to see if the tube amp is changing it.

That aside, the notion of "fatigue" often has little correlation to real performance of audio gear. If I listen to the same track 100 times on my system, I get fatigued. Does this mean something is wrong with the system?

 

[B&WTube]

We can't measure what is not real. The only way an amp can change the spatial effects is if it has non-flat response in the 1 to 3 kHz region which would be horrible design (but can happen due to high impedance). Outside of that, imaging effects are made up by people in evaluation of audio systems so there is nothing to measure. Look to the content for where these effects are created and to some extent, your speaker and positioning of them in the room.

Doesn't seem much like science if an effect is widely observed by thousands of people, but you say it isn't real because you can't tie and aspect of measurement to it. That's like saying the science has all been figured out, but as you probably know- it has not...and audio is one of the hardest sciences out there between all the components.

You are providing a tremendous service with this site. However, the subjective language/phenomena that you abhor, is exactly what you should be trying to bridge the gap to. Subjective reviews are all over the place, because there is no science to anchor to and there is money in reviewing with the best adjectives for the sound. I know you have to be getting sick of fighting all of the subjective folks, so why not work on the bridging the gaps? Why not tie measurable attributes to the cliché's of deep, wide, soundstage, decay, etc? Maybe it is as simple as a guide that bridges measuring aspects to certain common sound descriptors. I talked Erin H (Erin's audio corner), and he walked through aspects of his speaker measurements that produce certain aspects of the sound.

I know this sounds combative, but it is truly in the interest of moving audio forward and bringing more folks into understanding measurements (including myself). Even though I am complaining, please know how grateful I am for what you do. If there was anyone else who could pull this off, I would pester them- but you da man in this arena.

 

[rebbiputzmaker]

Tubes create distortion.

I hope you mean the equipment that you were testing and not the fact that the “vacuum tubes” create distortion because that really would not be totally accurate. There are some very good very low distortion tubes and also some extremely low distortion tube equipment. People might misunderstand what you say.

 

[SIY]

Doesn't seem much like science if an effect is widely observed by thousands of people, but you say it isn't real because you can't tie and aspect of measurement to it. That's like saying the science has all been figured out, but as you probably know- it has not...and audio is one of the hardest sciences out there between all the components.

You are providing a tremendous service with this site. However, the subjective language/phenomena that you abhor, is exactly what you should be trying to bridge the gap to. Subjective reviews are all over the place, because there is no science to anchor to and there is money in reviewing with the best adjectives for the sound. I know you have to be getting sick of fighting all of the subjective folks, so why not work on the bridging the gaps? Why not tie measurable attributes to the cliché's of deep, wide, soundstage, decay, etc? Maybe it is as simple as a guide that bridges measuring aspects to certain common sound descriptors. I talked Erin H (Erin's audio corner), and he walked through aspects of his speaker measurements that produce certain aspects of the sound.

I know this sounds combative, but it is truly in the interest of moving audio forward and bringing more folks into understanding measurements (including myself). Even though I am complaining, please know how grateful I am for what you do. If there was anyone else who could pull this off, I would pester them- but you da man in this arena.

The question isn’t the existence of the effect, it’s the claim that it’s related to the electronics rather than recording, speakers, and room. It makes no technical sense and indeed no one has ever demonstrated it.

 

[amirm]

Why not tie measurable attributes to the cliché's of deep, wide, soundstage, decay, etc?

Why don't you ask me about the effect that gets the wife to come out of the kitchen and ask what has changed? What is she hearing from so far away?

You see where I am going? There is no bridging here. Listening observations need to be in controlled testing. Ad-hoc listening in these areas is full of nuisance variables. Nothing can explain them until you remove those and give the precise data that the ear captured and brain interpreted.

 

[DSJR]

Compression and slight 'breathlessness' in the power output in the reproduced sound does wonders for 'soundstage depth' I remember. Vinyl sources thrive on the former...

 

[MattHooper]

The question isn’t the existence of the effect, it’s the claim that it’s related to the electronics rather than recording, speakers, and room. It makes no technical sense and indeed no one has ever demonstrated it.

That brings up the question of how it would be demonstrated.

I admit that as I'm switching between two different sets of tubes on my amp I'm perceiving what seems to be a very distinct expansion of the soundstage and imaging with different power tubes (KT120s seem to produce the "bigger" sound over the 6550s). I also of course hold out that it could be my imagination.

But if I am actually hearing a real sonic change that results in the impression of a bigger sound stage, how would that be demonstrated?

After all, even if it had an objective cause, the sensation it causes - a larger soundstage - is still perceptual. It seems then we have to rely on (replicable) perceptual reports to "demonstrate" this. That is, asking the participant what he perceives.

So for instance, if I did a blind test between the amps with different tubes, and reliably identified between them, and you ask "what sonic attributes allowed you to identify each tube set" and I replied "the soundstage and imaging was bigger on tubes X"...would that count as a demonstration, or at least some evidence for the proposition?

(Btw, I actually would enjoy doing a blind test like that if it were possible or not too difficult in my set up).

 

[SIY]

That brings up the question of how it would be demonstrated.

I admit that as I'm switching between two different sets of tubes on my amp I'm perceiving what seems to be a very distinct expansion of the soundstage and imaging with different power tubes (KT120s seem to produce the "bigger" sound over the 6550s). I also of course hold out that it could be my imagination.

But if I am actually hearing a real sonic change that results in the impression of a bigger sound stage, how would that be demonstrated?

After all, even if it had an objective cause, the sensation it causes - a larger soundstage - is still perceptual. It seems then we have to rely on (replicable) perceptual reports to "demonstrate" this. That is, asking the participant what he perceives.

So for instance, if I did a blind test between the amps with different tubes, and reliably identified between them, and you ask "what sonic attributes allowed you to identify each tube set" and I replied "the soundstage and imaging was bigger on tubes X"...would that count as a demonstration, or at least some evidence for the proposition?

(Btw, I actually would enjoy doing a blind test like that if it were possible or not too difficult in my set up).

With basic controls, same as any other audibility claim.

 

[MattHooper]

With basic controls, same as any other audibility claim.

So that would be: Yes, the scenario I just described (proper blind testing) would be a demonstration of the claim.

Correct?

(There's a reason I asked the question in the way I did: in a blind test someone could still report something that remains implausible, right?).

 

[SIY]

So that would be: Yes, the scenario I just described (proper blind testing) would be a demonstration of the claim.

Correct?

(There's a reason I asked the question in the way I did: in a blind test someone could still report something that remains implausible, right?).

First, specify what you’re trying to determine. What is the specific hypothesis you’re trying to falsify? Once that’s done, then you can move on to experimental design.

 

[MattHooper]

First, specify what you’re trying to determine. What is the specific hypothesis you’re trying to falsify? Once that’s done, then you can move on to experimental design.

I thought it was clear from the example I gave: Does swapping between KT120 and 6550 tubes in my amp alter the signal in a way that is perceived as altering the size of the soundstage?

So, would my employing proper blind testing be sufficient to demonstrate this, or provide some evidence in it's favor?

What test would suffice for you to think such a claim was "demonstrated"?

 

[don'ttrustauthority]

We can't measure what is not real. The only way an amp can change the spatial effects is if it has non-flat response in the 1 to 3 kHz region which would be horrible design (but can happen due to high impedance). Outside of that, imaging effects are made up by people in evaluation of audio systems so there is nothing to measure. Look to the content for where these effects are created and to some extent, your speaker and positioning of them in the room.

And I think we can measure soundstage. Begin with an even dispersal pattern that is wide, no coincident room modes that make interference, closely matched drivers that don't interfere with one another ... I think if you measured enough data points you could narrow down some that work.