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VTA ST-70 Review (Stereo Tube Amplifier)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 125 62.5%
  • 2. Not terrible (postman panther)

    Votes: 47 23.5%
  • 3. Fine (happy panther)

    Votes: 17 8.5%
  • 4. Great (golfing panther)

    Votes: 11 5.5%

  • Total voters
    200

MattHooper

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Oh well...
 

SIY

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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"?
Perceived by whom? You? Everyone?

Let me assume the former. I'd start by recording the electrical signal at the speakers under both conditions, then level match them and see if you could hear any difference. If you think you can, move on to ABX.
 

MattHooper

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Thanks for getting back to me, SIY!
Perceived by whom? You? Everyone?

I'd start with me, but then it makes sense if we were to try to understand the phenomenon more generally, then more people would be involved.

Just to be clear: The reason I asked you the original question is because this seems to get in to an interesting area of "what can be demonstrated, how, and at what point and by whom it would be considered 'demonstrated.'"

In this case, since the subject had been the claim of soundstaging/imaging being altered by equipment, you had replied:

"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."

Which got me wondering what WOULD demonstrate the effect...and who decides and why when it has been "demonstrated?" Since you were the one who made that comment, I was trying to focus first on what YOU would consider a "demonstration" of the phenomenon you say "has never been demonstrated."

I just used my own recent experience with tubes as a handy specific reference to get the ball rolling, but I suppose I could just avoid complications of me having to propose examples, and simply ask you "what specifically did you mean had not been demonstrated, and how WOULD "it" be demonstrated?"

Again, it's not some sort of "gocha" but I think it gets at interesting questions on how various claims can be demonstrated, which might change among individuals.

But, if we want to continue with my tube amps as an example.


Let me assume the former. I'd start by recording the electrical signal at the speakers under both conditions, then level match them and see if you could hear any difference. If you think you can, move on to ABX.

Just so I understood: Do you mean use a voltmeter at the speaker terminals to match volume, and then if I still think I hear a difference, move on to ABX?

If so...how do you suggest I would ABX between the different tubes?

And this brings me back around to the reason for the question.

Let's say I claimed changing tubes in my amp altered the imaging/soundstaging. Then I passed an ABX test. And I say that what allowed me to discern between the change in tubes was "the fact I heard the soundstaging/imaging changing."

Would you then consider the claim that changing tubes had been "demonstrated" to your satisfaction? (*Even if you still found the idea technically implausible?)
 

SIY

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Thanks for getting back to me, SIY!


I'd start with me, but then it makes sense if we were to try to understand the phenomenon more generally, then more people would be involved.

Just to be clear: The reason I asked you the original question is because this seems to get in to an interesting area of "what can be demonstrated, how, and at what point and by whom it would be considered 'demonstrated.'"

In this case, since the subject had been the claim of soundstaging/imaging being altered by equipment, you had replied:

"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."

Which got me wondering what WOULD demonstrate the effect...and who decides and why when it has been "demonstrated?" Since you were the one who made that comment, I was trying to focus first on what YOU would consider a "demonstration" of the phenomenon you say "has never been demonstrated."

I just used my own recent experience with tubes as a handy specific reference to get the ball rolling, but I suppose I could just avoid complications of me having to propose examples, and simply ask you "what specifically did you mean had not been demonstrated, and how WOULD "it" be demonstrated?"

Again, it's not some sort of "gocha" but I think it gets at interesting questions on how various claims can be demonstrated, which might change among individuals.

But, if we want to continue with my tube amps as an example.




Just so I understood: Do you mean use a voltmeter at the speaker terminals to match volume, and then if I still think I hear a difference, move on to ABX?

If so...how do you suggest I would ABX between the different tubes?

And this brings me back around to the reason for the question.

Let's say I claimed changing tubes in my amp altered the imaging/soundstaging. Then I passed an ABX test. And I say that what allowed me to discern between the change in tubes was "the fact I heard the soundstaging/imaging changing."

Would you then consider the claim that changing tubes had been "demonstrated" to your satisfaction? (*Even if you still found the idea technically implausible?)
Level matching is easier to do in software.
 

MattHooper

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Level matching is easier to do in software.

Can you go in to more detail, please?

What do you mean specifically by "recording the electrical signal at the speakers?"

Do you mean somehow recording the musical signal at the speaker terminals? If so, how do you suggest one do that?
But if changing tube amps alter the sound by, say, some impedance interaction with the speaker, would that suffice to capture it?
Wouldn't we want to hear the sound produced by the speakers?

Or, did you actually mean record the sound coming from the speakers with a microphone?

And then level match those files, then play them back through the speakers?
 

SIY

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Can you go in to more detail, please?

What do you mean specifically by "recording the electrical signal at the speakers?"

Do you mean somehow recording the musical signal at the speaker terminals? If so, how do you suggest one do that?
But if changing tube amps alter the sound by, say, some impedance interaction with the speaker, would that suffice to capture it?
Wouldn't we want to hear the sound produced by the speakers?

Or, did you actually mean record the sound coming from the speakers with a microphone?

And then level match those files, then play them back through the speakers?
Electrical signal.
 

MattHooper

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Electrical signal.

Ok thanks.

But I'd also asked how exactly you'd suggest to record the electrical signal at the speakers. (And also if this would actually
capture all the ways the sound would be affected that comes out of the speakers - e.g. if the amp interacted with the impedance
of the speakers to change the sound coming out of the speakers, would recording...wherever exactly you mean to record...capture
that phenomena?)

Maybe I'm just too thick but I keep asking for more detail while getting replies so terse I have to keep asking more questions.

I can see this pattern is likely to be repeated, and I also asked other pertinent questions (e.g. would my passing an ABX test demonstrate anything to you) but your replies are suggesting a lack of engagement or interest, so I won't bother you with any more questions.

Thanks.
 

SIY

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Ok thanks.

But I'd also asked how exactly you'd suggest to record the electrical signal at the speakers. (And also if this would actually
capture all the ways the sound would be affected that comes out of the speakers - e.g. if the amp interacted with the impedance
of the speakers to change the sound coming out of the speakers, would recording...wherever exactly you mean to record...capture
that phenomena?)

Maybe I'm just too thick but I keep asking for more detail while getting replies so terse I have to keep asking more questions.

I can see this pattern is likely to be repeated, and I also asked other pertinent questions (e.g. would my passing an ABX test demonstrate anything to you) but your replies are suggesting a lack of engagement or interest, so I won't bother you with any more questions.

Thanks.
I would use an ADC for recording. Good ones are relatively inexpensive these days.
 

pseudoid

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Evidence is far better than handwaving.
Not if you are the Conductor in front of the orchestra and the audience behind.;)
I would use an ADC for recording. Good ones are relatively inexpensive these days.
I am all confused about what you are wanting to "measure" via the recording by an ADC.
Is this ADC more of a comparator than a 'measurer' of some complex audio signal (not 2-beat IM) ALONG with all of its constituents?
This is getting confusing, as if we are looking for replication of a soundstage with detection of well placed instruments (musical kinds) a simple ADC measurement maybe for naught.
 

SIY

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Not if you are the Conductor in front of the orchestra and the audience behind.;)

I am all confused about what you are wanting to "measure" via the recording by an ADC.
Is this ADC more of a comparator than a 'measurer' of some complex audio signal (not 2-beat IM) ALONG with all of its constituents?
This is getting confusing, as if we are looking for replication of a soundstage with detection of well placed instruments (musical kinds) a simple ADC measurement maybe for naught.
The ADC is a recorder so that level matched listenable files can be generated to determine audibility. And if audibility turns out to be real, they can then be analyzed to get at the cause.
 

rebbiputzmaker

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Thanks for getting back to me, SIY!


I'd start with me, but then it makes sense if we were to try to understand the phenomenon more generally, then more people would be involved.

Just to be clear: The reason I asked you the original question is because this seems to get in to an interesting area of "what can be demonstrated, how, and at what point and by whom it would be considered 'demonstrated.'"

In this case, since the subject had been the claim of soundstaging/imaging being altered by equipment, you had replied:

"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."

Which got me wondering what WOULD demonstrate the effect...and who decides and why when it has been "demonstrated?" Since you were the one who made that comment, I was trying to focus first on what YOU would consider a "demonstration" of the phenomenon you say "has never been demonstrated."

I just used my own recent experience with tubes as a handy specific reference to get the ball rolling, but I suppose I could just avoid complications of me having to propose examples, and simply ask you "what specifically did you mean had not been demonstrated, and how WOULD "it" be demonstrated?"

Again, it's not some sort of "gocha" but I think it gets at interesting questions on how various claims can be demonstrated, which might change among individuals.

But, if we want to continue with my tube amps as an example.




Just so I understood: Do you mean use a voltmeter at the speaker terminals to match volume, and then if I still think I hear a difference, move on to ABX?

If so...how do you suggest I would ABX between the different tubes?

And this brings me back around to the reason for the question.

Let's say I claimed changing tubes in my amp altered the imaging/soundstaging. Then I passed an ABX test. And I say that what allowed me to discern between the change in tubes was "the fact I heard the soundstaging/imaging changing."

Would you then consider the claim that changing tubes had been "demonstrated" to your satisfaction? (*Even if you still found the idea technically implausible?)
Not wanting to get too deep into this conversation but just a point my opinion and possible clarity or not. You are not going to be able to measure any of the differences that you hear. The difference that you are hearing are possibly caused by alterations to the harmonic distribution or different slight frequency shifts . The differences are audible imo and I would say repeatable in general, but not necessarily measurable and not really exactly definable, as better worse etc. imo. Just different, and this is where the importance to the individual comes in if you find a difference that you prefer cool enjoy it and keep it moving. It’s too much of a reach to try to attach exact measurements or reasoning behind the differences. Ymmv.
 

SIY

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Not wanting to get too deep into this conversation but just a point my opinion and possible clarity or not. You are not going to be able to measure any of the differences that you hear. The difference that you are hearing are possibly caused by alterations to the harmonic distribution or different slight frequency shifts . The differences are audible imo and I would say repeatable in general, but not necessarily measurable and not really exactly definable, as better worse etc. imo. Just different, and this is where the importance to the individual comes in if you find a difference that you prefer cool enjoy it and keep it moving. It’s too much of a reach to try to attach exact measurements or reasoning behind the differences. Ymmv.
Everything you mentioned is absolutely and trivially measurable.
 

BDWoody

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It’s too much of a reach to try to attach exact measurements or reasoning behind the differences.

Unless you want to understand what's actually happening.
 

MattHooper

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As I said in earlier posts, simply repeating you should "record the electrical signal at the speakers" doesn't answer the questions I kept raising.

All the A to D converters I'm aware of or have used are made for low level signal inputs (e.g. from RCAs etc) NOT the high level amplified output from an amplifier. I have a Benchmark DAC 2L and for work I use an Apogee Duet. They expect line level inputs (the Apogee includes mic/instrument level inputs). They are not designed to accept the signal from speaker level outputs:


"IMPORTANT: You should never plug a speaker level signal into a source expecting anything less than a speaker level signal."

Hence my obvious question to SIY about how he suggests one do this recording.

In fact I phoned my local pro audio gear shop and the technicians there (who work with amps etc) said you really don't want to do that. In fact the idea was tossed around various techs at the place. Not only did they say they have no A to D converters that would take a high level speaker output signal, they said the suggestion doesn't really make sense as a test for differences in a tube amp's performance because what you want to see is how the amp plays with a reactive load - e.g. the speaker. Which is one of the things I pointed out.

Now there may be something I'm missing (I'm not a techie), and those techs haven't understood. SIY has something in mind. But these were the questions I was trying to clarify with SIY, but with no luck.

(And, really, one of the reasons I was asking to begin with is "what would constitute a demonstration" for SIY...e.g. what IF I passed a blind ABX test, and reported that it was changes in soundstaging/imaging that was the cue. Would he consider the phenomenon "demonstrated?"
But again...no luck in pursuing that either).
 
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pseudoid

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Not wanting to get too deep into this conversation
You are knee-deep in it; whether you want in or out... ;) !!stay!!
But again...no luck in pursuing that either...
Mattski, you are doing great; whether you feel lucky or not... ;) !!don't stop digging!!
...Not only did they say they have no A to D converters...
They may not have the hardware but if the technologies currently exist to readily convert/resolve 11.2-channels down to 2-channels (and vice-versa) with fair amount of signal integrity and can achieve software-based equalization for (multi-channel) signal- and/or room-corrections; then, it is a given that the technology does exist but maybe its application for what @SIY is seeking MAY not.
 

rebbiputzmaker

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Unless you want to understand what's actually happening.
You’re still not really going know. The Example above plugging in two different output tubes probably would slightly change the operating points and the tubes have different characteristics not gonna be very measurable so how are you going to measure that so you’re not going to know anything definitive. A relative waste of time more than likely. Trying to find something that does not really mean much in the big scheme of things.
 

SIY

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You’re still not really going know. The Example above plugging in two different output tubes probably would slightly change the operating points and the tubes have different characteristics not gonna be very measurable so how are you going to measure that so you’re not going to know anything definitive. A relative waste of time more than likely. Trying to find something that does not really mean much in the big scheme of things.
It will be easily measurable, and if anyone wants to bother, easy to do a controlled listening comparison.
 

SIY

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As I said in earlier posts, simply repeating you should "record the electrical signal at the speakers" doesn't answer the questions I kept raising.

All the A to D converters I'm aware of or have used are made for low level signal inputs (e.g. from RCAs etc) NOT the high level amplified output from an amplifier. I have a Benchmark DAC 2L and for work I use an Apogee Duet. They expect line level inputs (the Apogee includes mic/instrument level inputs). They are not designed to accept the signal from speaker level outputs:


"IMPORTANT: You should never plug a speaker level signal into a source expecting anything less than a speaker level signal."

Hence my obvious question to SIY about how he suggests one do this recording.

In fact I phoned my local pro audio gear shop and the technicians there (who work with amps etc) said you really don't want to do that. In fact the idea was tossed around various techs at the place. Not only did they say they have no A to D converters that would take a high level speaker output signal, they said the suggestion doesn't really make sense as a test for differences in a tube amp's performance because what you want to see is how the amp plays with a reactive load - e.g. the speaker. Which is one of the things I pointed out.

Now there may be something I'm missing (I'm not a techie), and those techs haven't understood. SIY has something in mind. But these were the questions I was trying to clarify with SIY, but with no luck.

(And, really, one of the reasons I was asking to begin with is "what would constitute a demonstration" for SIY...e.g. what IF I passed a blind ABX test, and reported that it was changes in soundstaging/imaging that was the cue. Would he consider the phenomenon "demonstrated?"
But again...no luck in pursuing that either).
Wouldn’t it be really cool if there were some magic technology to scale down voltage levels?
 

MattHooper

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Wouldn’t it be really cool if there were some magic technology to scale down voltage levels?

From early on I made it very clear that I'm not sure precisely what you were suggesting and how to accomplish it. I kept asking for specific details. You kept repeating answers missing the detail I was asking you for, that you could have easily given if you have the answers, to the point I even had to take the question to my local pro audio shop, who pointed out issues with your suggestion.

Given you are now down to facetious hint-dropping instead of just being clear with specific information, after all this time, unfortunately it implies your goal was not really about being helpful.

Too bad. Could have been an interesting conversation. Towel is thrown in.
 
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