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ABX Blind Test and Level Matching

MarkWinston

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I am ready to do an ABX test on the assertion that all good and competent amps (integrateds in this case) sound exactly the same and Im aware that volume/level matching is one of the most, if not the most, important thing in an ABX test. Question here is what is the best and accurate way to volume match without the need of any expensive equipment? Also, my wife will play the switcher, that way Im confident that no one is trying to fool me into listening to the same amp. What is the best way to conduct this test? All fresh suggestions would be helpful. If all good amps sound the same below clipping levels, that would save me a lot of money and time. TIA.
 

tomelex

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You need to know a whole lot more about electronics and amplifier design to make your test hold up to scrutiny. A 20W amp and another 20W rated amp (into an 8 ohm resistive load) indeed could very well sound different on speakers when you start to drive them with more power. If you head is not locked in a vise (in exact position), your experiment is not valid no matter what other controls you use. I will not go on and on but have fun with your experiments Mark.
 

Pdxwayne

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I am ready to do an ABX test on the assertion that all good and competent amps (integrateds in this case) sound exactly the same and Im aware that volume/level matching is one of the most, if not the most, important thing in an ABX test. Question here is what is the best and accurate way to volume match without the need of any expensive equipment? Also, my wife will play the switcher, that way Im confident that no one is trying to fool me into listening to the same amp. What is the best way to conduct this test? All fresh suggestions would be helpful. If all good amps sound the same below clipping levels, that would save me a lot of money and time. TIA.
May I suggest you try to assess your own hearing sensitivity first?

You can start by doing sound pressure online blind tests available here:
https://www.audiocheck.net/blindtests_level.php?lvl=0.5

Start with 1db, then try 0.5db, then lower if you are able to pass 0.5db.

You can then try other tests there too. Post your results here.

My blind tests results are here:

https://www.audiosciencereview.com/...tracking-my-listening-tests.24364/post-822052

In there, there are links for other type of tests you can try, including distortion tests.
 
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somebodyelse

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I usually use a multimeter to match AC volts at the speaker terminals, using a sine wave source under 400Hz as some cheap meters don't work reliably at frequencies much above that. The source can be a test cd, software like REW or sox, or a media player playing some suitable test files. Make sure you start with the source volume low! I'm assuming that one or both of your amps has a volume control so you can match levels with the same source driving both amps.

You'll need to work on the test method to check that you can't tell which amp it is by the sound of the changeover, tone of voice or other unconscious cues from your helper
 

DVDdoug

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You can measure voltage to the speakers with a multimeter (AKA "DMM" = digital multi-meter). And you can generate a test-tone file with Audacity (regular program material jumps around too much to measure accurately). Just about any meter will work... It doesn't have to be super-accurate, just repeatable and stable. Note that some meters don't measure low AC voltages accurately (I have one like that) so if you ever want to measure line level signals (around 1V or less depending on the "loudness" and volume control) make sure to get one with a low-AC range.

Also, my wife will play the switcher, that way Im confident that no one is trying to fool me into listening to the same amp.
In case you haven't seen this - HydrogenAudio - What is an ABX test?

Theoretically, it's supposed to be double-blind so she doesn't know what "X" is and she can't give you any clues, accidentally or intentionally to fool you or help you. But double-blind is not usually easy or practical so try to set it up so you can't see her face and if possible she shouldn't say anything (or say very little). You can ask for "A", "B", or "X" and you can give your answer/guess and move on to the next trial. (You need multiple trials to get a statistically valid result.)

"A" and "B" can be known. "X" should be truly random (a coin flip, etc.). She can flip a coin in advance and make a "secret sequence" list after you've decided on a number of trials. and you can ask to hear "A", "B", or "X" again until you make a decision or a guess.

Do you have an easy way to switch and an easy way to switch off between switches so you can't tell if it was switched or not?

You may already know this too, but ABX doesn't tell you which is better it just tells you if you can reliably hear a difference between "A" & "B".
 
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MarkWinston

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You can measure voltage to the speakers with a multimeter (AKA "DMM" = digital multi-meter). And you can generate a test-tone file with Audacity (regular program material jumps around too much to measure accurately). Just about any meter will work... It doesn't have to be super-accurate, just repeatable and stable. Note that some meters don't measure low AC voltages accurately (I have one like that) so if you ever want to measure line level signals (around 1V or less depending on the "loudness" and volume control) make sure to get one with a low-AC range.

In case you haven't seen this - HydrogenAudio - What is an ABX test?

Theoretically, it's supposed to be double-blind so she doesn't know what "X" is and she can't give you any clues, accidentally or intentionally to fool you or help you. But double-blind is not usually easy or practical so try to set it up so you can't see her face and if possible she shouldn't say anything (or say very little). You can ask for "A", "B", or "X" and you can give your answer/guess and move on to the next trial. (You need multiple trials to get a statistically valid result.)

"A" and "B" can be known. "X" should be truly random (a coin flip, etc.). She can flip a coin in advance and make a "secret sequence" list after you've decided on a number of trials. and you can ask to hear "A", "B", or "X" again until you make a decision or a guess.

Do you have an easy way to switch and an easy way to switch off between switches so you can't tell if it was switched or not?

You may already know this too, but ABX doesn't tell you which is better it just tells you if you can reliably hear a difference between "A" & "B".

I just want to test for a difference between amps, do I still need to do an ABX or is AB sufficient?
 

DVDdoug

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I just want to test for a difference between amps, do I still need to do an ABX or is AB sufficient?
You can do whatever you want! ;)

But if you're going to do a blind test you might as well add the "X" (unknown) to "prove" to yourself that you can actually-reliably hear a difference.

A/B can be useful if there is a difference that you can clearly hear. For example, if amp-A has more bass than amp-B, etc. But, you can fool yourself... Audiophiles often claim a "night and day" difference that suddenly becomes difficult or impossible to hear in a blind test and then they start telling you all the things that are wrong with your blind test setup, or they say blind testing causes too much stress, etc.

The most likely audible difference is noise (typically hiss) and that might be obvious enough (especially with silence) that there is no need for a blind test.

If you get it right 100% of the time, you 've got a clear answer. If you get it right 80% of the time you know it's hard to hear a difference (because you are wrong 20% of the time) or it's just random luck. If you get it right about 50% of the time you're probably "just guessing" and maybe thinking you're hearing a difference.


...An alternative (possibly free) to a multimeter is an SPL app for your smart phone. Acoustic measurements aren't as "stable" as electrical measurements, but again you don't need absolute accuracy as long as you get the same reading with both amps.


ABX has a particular purpose... To demonstrate if there is an audible difference or not. A LOT of stuff is legitimately done without blind listening or even A/B. Amir doesn't do blind listening as part of his routing testing/listening. If you EQ to taste, or measure and EQ your speakers/room and/or treating your room you aren't A/B testing (although you should have a before and after measurement if you're measuring your room, and of course you're going to listen before and after). When a mixing or mastering engineer is working on an audio production they might A/B their adjustments or A/B with a known-good reference recording, but that stuff is never blind or ABX. Or if your left speaker is dead there's no need for A/B or ABX...
 
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ahofer

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I'd say start with white noise and a db meter first to determine a volume adjustment setting between the amps and just do an A/B test. It wouldn't nearly pass strict scientific scrutiny, but in my experience it was enough to be a revelation of what I could and couldn't hear.

If you hear the difference and can ID the amps blind after that, you can go to the next step.
 

Jimbob54

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May I suggest you try to assess your own hearing sensitivity first?

You can try by doing sound pressure online blind tests available here:
https://www.audiocheck.net/blindtests_level.php?lvl=0.5

Start with 1db, then try 0.5db, then lower if you are able to pass 0.5db.

You can try other tests there too. Post your results here.

My blind tests results are here:

https://www.audiosciencereview.com/...tracking-my-listening-tests.24364/post-822052

Why does that matter? As long as the levels are matched accurately and the test run properly, the results still only ever apply to @MarkWinston anyway. Without a conclusive result to the ABX AND measurements of the amps he isnt going to know if the amps sound the same because they are measurably the same or because he cant hear the difference.
 

Pdxwayne

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Why does that matter? As long as the levels are matched accurately and the test run properly, the results still only ever apply to @MarkWinston anyway. Without a conclusive result to the ABX AND measurements of the amps he isnt going to know if the amps sound the same because they are measurably the same or because he cant hear the difference.
What is the value of telling all of us some amps sound the same if it only applies to him?

Wouldn't it be nice we also get additional information out of this?

For example, if he can't hear a difference, what kind of hearing sensitive he has?

If he can sense a difference, what kind of hearing sensitivity he has?
 

Jimbob54

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What is the value of telling all of us some amps sound the same if it only applies to him?

Wouldn't it be nice we also get additional information out of this?

For example, if he can't hear a difference, what kind of hearing sensitive he has?

If he can sense a difference, what kind of hearing sensitivity he has?
So if he can hear a 0.5db shift in volume on a 400hz tone on the same amp , what does that tell us about his findings on 2 amps with different harmonic distortion profiles but that were level matched to less than half a dB but playing music ? You're talking about apples and onions.
 

Pdxwayne

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So if he can hear a 0.5db shift in volume on a 400hz tone on the same amp , what does that tell us about his findings on 2 amps with different harmonic distortion profiles but that were level matched to less than half a dB but playing music ? You're talking about apples and onions.
I meant to say "start" with certain tests. I didn't suggest him "only" do dB tests.

There is a reason I provided a couple of links for him. My own thread has a couple of distortion ABX he can try.
 

Jimbob54

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I said "start" with certain tests. I didn't suggest him "only" do dB tests.

There is a reason I provided a link for him. There are a couple of distortion ABX in my link.
Fair enough, but I'm still not sure what the point of doing the online listening tests is for Mark. His hearing is what it is, good or bad. All he wants to determine is whether he can tell the difference between his amps.

How good his hearing is isn't the matter under test.
 

Pdxwayne

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Fair enough, but I'm still not sure what the point of doing the online listening tests is for Mark. His hearing is what it is, good or bad. All he wants to determine is whether he can tell the difference between his amps.

How good his hearing is isn't the matter under test.
Are you sure this information will only be used by him and never referenced by others as "proof" that amps sound the same?
 

Jimbob54

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Are you sure this information will only be used by him and never referenced by others as "proof" that amps sound the same?

Others can use it however they like. Good luck to anyone trying to support an argument by quoting one guys (no offence to mark here) unvalidated abx test the results of which are posted on the Internet.

The results will have meaning to him in making any future purchase /sale decisions. Other than that, everyone else will continue regardless.

If the results go in a way he wasn't expecting, then maybe seeing how sensitive he is might be interesting.
 

Pdxwayne

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Others can use it however they like. Good luck to anyone trying to support an argument by quoting one guys (no offence to mark here) unvalidated abx test the results of which are posted on the Internet.

The results will have meaning to him in making any future purchase /sale decisions. Other than that, everyone else will continue regardless.

If the results go in a way he wasn't expecting, then maybe seeing how sensitive he is might be interesting.
Well, even if he can't hear a difference, that doesn't mean too much yet in regard to how it would influence his future purchases.

There might be other things that prevent OP from hearing a difference between amps.

Questions like these come to mind:
*OP has a transparent chain before the amp?

*OP has a good pair of speakers that can reveal very small differences?

*OP has a room that is quite enough and don't have too much room related issue?

etc. etc....
 

Jimbob54

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Well, even if he can't hear a difference, that doesn't mean too much yet in regard to how it would influence his future purchases.

There might be other things that prevent OP from hearing a difference between amps.

For example:
*OP has a transparent chain before the amp?

*OP has a good pair of speakers that can reveal very small differences?

*OP got a room that is quite enough and don't have too much room related issue?

etc. etc....

If he knows how they measure it matters an awful lot. Being overly simplistic and using SINAD as a convenient example, if he knows the amps under test are 60, 70 and 80 SINAD but he can't discern, why spend good money on any well measuring amp in the future for anything other than aesthetic or power reasons?
 

Pdxwayne

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If he knows how they measure it matters an awful lot. Being overly simplistic and using SINAD as a convenient example, if he knows the amps under test are 60, 70 and 80 SINAD but he can't discern, why spend good money on any well measuring amp in the future for anything other than aesthetic or power reasons?
Being overly simplistic, I am going to assume most people, including the OP, won't sense a difference between decent integrated amps.

Amyway, if OP can do all those online blind tests and then find out that he is not sensitive at all, he could simply give up doing ABX and save a lot of time and hassles.
; )
 
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