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Amplifier comparison: March Audio P452 (Purifi 1ET400A) vs Buckeye Hypex NC502MP vs AIYIMA A07 (TPA3255) vs Onkyo TX-NR737 (125W Class AB)

dlaloum

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On the topic of hearing acuity - can you detect a 0.5db difference...

some years back I digitised a series of tracks from vinyl, using different cartridges - I carefully level matched them... to within 1db

They sounded substantially different - each cartridge had its own character - very clearly so

After participating in various discussions about hearing etc... I returned to those tracks, and level matched them to under 0.5db

Keeping in mind that these are phono cartridges - mechanical transducers - their responses are measurably different in various ways frequency response being the most obvious one! - I level matched them based on the average level measured across the entire track - and carefully matched the start and end point of the track. - Each cartridge had also been individually adjusted both mechanically, and electrically (ie capacitance and resistive loads) to achieve the most neutral possible response.

at a matching of better than 0.5db average - I could not discern differences without very very careful repeated listening, and switching back and forth - and even then, it may all have been psychological - I am not convinced that double blind, I could tell them appart.

At a matching of only +/-1db - they were distinctly different - and easily seperated

In terms of how loud they sounded - with either matching option, they all sounded like they were the same loudness - there was no discernible difference in loudness.

The three components in the audio chain, that are the least linear, and therefore have the most impact on the "character" or "Voicing" of what we hear, are the microphone, the cartridge (if talking vinyl), and the speakers.

It is very valuable as an individual to do these kind of tests, and become aware of the limits of our hearing acuity - once you truly realise this (!!!) - then you can start to ignore (or weight them more lightly in your evaluations) a whole category of measurements, in the knowledge that although they can and do have an impact, in the overall scheme of things, they may not be all that important!!
 
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f1shb0n3

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One thing I am very curious about is your own hearing sensitivity.
For example, can you sense 0.5db of sound pressure difference?
Thanks for insisting on the highest standards for content, we definitely need to get all our favorite popular reviewers to go through such tests to increase their credibility ;)
As for myself - I don't claim to have any listening skills or special hearing capabilities, so don't read too much in my ability or inability to hear tiny differences of any kind. Definitely nice to check though for my own understanding and practice can probably improve these skills.

Did the volume difference test - I know from prior experience comparing DACs that 0.2dB is easy for me to hear as a difference especially after some practice and when having a switch to pick myself. At this test I could always hear the Up, very confidently at 0.2dB even, but Down is very hard to distinguish from Flat at 0.2dB. The 0.2dB test below I got lucky to have many Ups and this is how I got this score, not representative of my average skill in that.

0.5db volume test.png
0.2db volume test.png

How good are you in sensing distortions?
Horrible in hearing distortion - tried similar ones before. Checked out the Klippel one you linked - using "two-tone 70Hz 800Hz" failed twice at -39dB and giving up trying. The website also has some issues playing tones after awhile, don't want to deal with that.
 
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dlaloum

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Try doing the level tests with audiophile music tracks - some of the high res samplers - see if you can still discern that 0.2db ...
 

Sal1950

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These are basic function tests that I would appreciate having in ASR reviews. It's not BS, simply full disclosure.
I'm with you there, but it is hard to remember to test for every function. Can you imagine trying to test every function on a modern AVR? Also he has limited time with most every component.
The BS reference was to subjective SQ pronouncements.
As to optical ports, it's impossible for him to test for reliable function on your gear. The quality of the sources transmitter varies (a lot) from unit to unit. Also here is a place where the cable can make a difference. The type of fiber, plastic or glass, and it's quality, along with it's length is important to toslink function at the higher data rates. 2channel 24/192hz is very ify on optical, 96 should be mostly ok. To be clear, I'm not talking about SQ, it either works, has intermittent dropouts, or won't work at all.
 
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f1shb0n3

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Try doing the level tests with audiophile music tracks - some of the high res samplers - see if you can still discern that 0.2db ...
True - probably won't with highly dynamic music. What I suspect though (based on some limited experience with comparisons) is that 0.2dB "could" be perceived as a difference of another kind - crisper treble, more resolution, deeper soundstage, etc. especially when putting your whole focus on trying to discern differences between A and B which are basically so similar that the 0.2dB difference between then, maybe even consciously imperceivable as such, is experienced as another trait.
 

Pdxwayne

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Thanks for insisting on the highest standards for content, we definitely need to get all our favorite popular reviewers to go through such tests to increase their credibility ;)
As for myself - I don't claim to have any listening skills or special hearing capabilities, so don't read too much in my ability or inability to hear tiny differences of any kind. Definitely nice to check though for my own understanding and practice can probably improve these skills.

Did the volume difference test - I know from prior experience comparing DACs that 0.2dB is easy for me to hear as a difference especially after some practice and when having a switch to pick myself. At this test I could always hear the Up, very confidently at 0.2dB even, but Down is very hard to distinguish from Flat at 0.2dB. The 0.2dB test below I got lucky to have many Ups and this is how I got this score, not representative of my average skill in that.



Horrible in hearing distortion - tried similar ones before. Checked out the Klippel one you linked - using "two-tone 70Hz 800Hz" failed twice at -39dB and giving up trying. The website also has some issues playing tones after awhile, don't want to deal with that.
Thanks for trying!

May I know your listening chain?
 

Pdxwayne

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True - probably won't with highly dynamic music. What I suspect though (based on some limited experience with comparisons) is that 0.2dB "could" be perceived as a difference of another kind - crisper treble, more resolution, deeper soundstage, etc. especially when putting your whole focus on trying to discern differences between A and B which are basically so similar that the 0.2dB difference between then, maybe even consciously imperceivable as such, is experienced as another trait.
Talking about test music, maybe try a metal type like this:

Then, listen for small differences in how the cymbals sound between your test amps.
 

Sal1950

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A fun cover of the Dire Straits song.
If the dude would only shut up and let the chick sing it would be a lot better. LOL
Shes hot.
 

dlaloum

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True - probably won't with highly dynamic music. What I suspect though (based on some limited experience with comparisons) is that 0.2dB "could" be perceived as a difference of another kind - crisper treble, more resolution, deeper soundstage, etc. especially when putting your whole focus on trying to discern differences between A and B which are basically so similar that the 0.2dB difference between then, maybe even consciously imperceivable as such, is experienced as another trait.
Those are the specific differences I was looking for, which were audible with 1db level differences, but became inaudible (or at least very difficult to discern) - when the difference dropped below 0.5db.

Your experience may differ.... ( you may have better hearing than I do)
 
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f1shb0n3

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Those are the specific differences I was looking for, which were audible with 1db level differences, but became inaudible (or at least very difficult to discern) - when the difference dropped below 0.5db.

Your experience may differ.... ( you may have better hearing than I do)
Exactly the same experience - when the difference in volume approaches your sensitivity threshold (which would be in the 1db - 0.2db range), while you focus intently on a frequency range or whatever other characteristic of sound, you perceive the difference in SPL as a difference in the observed characteristic. Thus volume matching being critically important, at most 0.1dB
 

Pdxwayne

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Exactly the same experience - when the difference in volume approaches your sensitivity threshold (which would be in the 1db - 0.2db range), while you focus intently on a frequency range or whatever other characteristic of sound, you perceive the difference in SPL as a difference in the observed characteristic. Thus volume matching being critically important, at most 0.1dB
Talking about volume matching, amps can have channel imbalance too.

I did abx of two amps recordings not too long ago and was able to successfully tell one from another due to channel imbalance of 0.3db for the right channel and 0.1db for left channel.

Have you checked if the amps channel balance are good within your 0.1db limit?
 

mrmojo2022

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Transducers (motors basically) and solid state devices are in completely different categories.
I'm really not clear on what that has to do with the point I'm making. the OP was criticised for posting subjective impressions that lacked controls and yet this is something Amir does in his speaker tests. the category of of product is irrelevant.
 

mrmojo2022

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Oh yes, hugely so.
Now we're talking of speakers/headphones only.
Amir presents the numbers and then attempts to relate what he hears in view of them. And add EQ at times talking about it's effects on the perceived sound
.
The only other measurer currently is Stereophiles John Atkinson, and if a product measures bad, he will always phoo phoo his own numbers if the subjective reviewer thinks the DUT sounds glorious.
He does this sighted after seeing the measurement data in a non comparative situation. Erins Audio Corner for example at least listens prior to acquiring data. you are right about Stereophile.
 

BDWoody

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Amir does in his speaker tests. the category of of product is irrelevant.

It is if one category isn't going to have identifiable differences. Demonstrating that every time would be pointless. He also doesn't really do head to head comparisons like this from what I can remember.

Speakers and headphones aren't as easily characterized purely by measurements.
 
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f1shb0n3

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Talking about volume matching, amps can have channel imbalance too.

I did abx of two amps recordings not too long ago and was able to successfully tell one from another due to channel imbalance of 0.3db for the right channel and 0.1db for left channel.

Have you checked if the amps channel balance are good within your 0.1db limit?
Yes - channels are balanced, confirmed with the oscilloscope.

I remember when I did a quick comparison of headphone amps RME ADI-2 vs Topping A30 and I realized that I’ll never ever use an amp with analog volume pot - the channel imbalance up to 3pm volume is very audible in comparison at surprisingly low threshold of difference similar to what you mentioned.
 
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Vain

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No problem. I like to get links to Peter's stuff out on occasion. Lord only knows how much longer biline.ca will continue to host Peter's stuff, he's been gone 5 years now. :(
The site is a goldmine of fun reading, with pdf's of every issue of The Audio Critic still downloadable.
I've got them all saved to my HD. LOL
Filled a few empty nights during the early lockdowns of Covid once again.
Put them on Google Drive and share them :) The biline site is slooooooooooow
 

mrmojo2022

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It is if one category isn't going to have identifiable differences. Demonstrating that every time would be pointless. He also doesn't really do head to head comparisons like this from what I can remember.

Speakers and headphones aren't as easily characterized purely by measurements.
You have so missed the point. never mind.
 

MasterApex

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I'll use this thread as my personal blog in The Quest to find The Answer to The Question about Amplifiers. My subjective one, informed by the best science known to me. Both the question and the answer are to be figured out, my first revision of the question is: "What are the audible differences between different power amplifiers?"

From my personal journey , the audible differences can only be audible with highly resolving speakers and with "listening' (not just measuring knowns metric,

I had compare amplifiers that I could not hear the difference when they are driving my Logan bookshelf speakers but can clearly hear the difference when driving highly resolving speakers like B&W 802D3 or Revel Ultima.
 

Sal1950

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I had compare amplifiers that I could not hear the difference when they are driving my Logan bookshelf speakers but can clearly hear the difference when driving highly resolving speakers like B&W 802D3 or Revel Ultima.
Would you please post the conditions under which you ran a bias controlled DBT of the un-named amplifiers?
 
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