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Amplifiers can you hear a diffrence?

Blumlein 88 said:
Yes and no.
In case A you have source>power amp>speaker.
In case B you have source>power amp>loudspeaker load>resistors to drop voltage>power amp>speaker.
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That's an interesting way to do it. Do you know what they used for the load?
 
maverickronin said:
That's an interesting way to do it. Do you know what they used for the load?
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I'll see if I can find the schematic. I don't know the speaker, but they made a simulated load that was very close to the real speaker they were using. It was rather demanding as I recall though not something crazy like some ESLs.

Okay here is the load they used. Made to mimic the loudspeaker. Miminum impedance of 3.5 ohms. The non-linear component was made with physically loose winding a coil and getting it to act like the voice coil in the speaker they were modeling. The speaker modeled was ported.
1588202921532.png


Here is the switching schematic which is more or less what I did as well even though I did it before them. It makes a big difference to be able to switch between wire and amp with the flick of a switch. Longer times between switching like a few minutes to swap amps would obscure some perceptible differences. Which begs the question of whether they are large enough to be important just for long term music listening.
1588203230384.png
 
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SIY said:
I have extremely high regard for @March Audio (which is no secret) and I'd be happy to use his amps. But... his support for that claim has not been very strong, and I think it's likely that this isn't right.
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Very small frequency tilts over a frequency range are audible. I don't usually use the "appeal to authority" but it is specifically mentioned in Floyd Tooles book so I think I'm on good ground here. ;)
 
It's the NC400 module thats .4dB down at 20kHZ, not really your amp, though, right? So assuming the NC400 was flat all the way up to 150kHz, your amp would measure flat that high too yeah?
 
direstraitsfan98 said:
It's the NC400 module thats .4dB down at 20kHZ, not really your amp, though, right? So assuming the NC400 was flat all the way up to 150kHz, your amp would measure flat that high too yeah?
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I'm not clear on what you are saying.

All the ncores are about 0.5 to 0.6dB down by 20khz. It's something you almost certainly wouldn't notice in isolation but if you quick switch between 2 amps it can be identified.
 
Dimitri said:
I just tried + 0.5db @ 7KHz , also -0.5db @ 7KHz . Couldn't hear the difference to to save my life.
I'm all set.
Not sure what type of bats Toole used that could hear 0.5 db difference @20KHz , but I know I'm not one.
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Its not a boost or cut at a specific frequency thats audible, its a tilt in frequency response - change over a range of frequencies. It will depend also on the spectral content of the music you are listening too and of course your hearing.
 
March Audio said:
Very small frequency tilts over a frequency range are audible. I don't usually use the "appeal to authority" but it is specifically mentioned in Floyd Tooles book so I think I'm on good ground here. ;)
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are we talking about a tilt being audible where a shorter step deviation would be inaudible?
 
makes sense from a sensory detection standpoint

what spec. needs to be given for 2 amps. to sound the same?
 
Here is a clip of white noise (not representative of music but shown to demonstrate the point) with a section filtered to be 0.5dB down at 20kHz. Its plain as day. Interestingly I find the change to the filtered section when it starts is less noticeable than when it ends.

If I listen through headphones I find it more obvious on my Oppo PM1 and Hifiman than on My HD650.

https://1drv.ms/u/s!AnQ0c7fb_4zLgRcWFtIV9ZIOju8k?e=UvJTh7


1588223354229.png
 
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Wes said:
are we talking about a tilt being audible where a shorter step deviation would be inaudible?
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Thats the way I understand it yes.

Again I have to emphasise we are not talking massive differences here, but detectable yes.

You also have to emphasise that your hearing range is going to impact this audibility significantly.
 
I hate saying things like this without finding the sources. I seem to recall .3 to .4 db response differences over 3 octaves as being audible in testing. My own idea is a tilt of +.5 to -.5 db over the band is detectable in fast switching. We do know that low Q resonances are audible at low levels while high Q resonances may not be noticed until very large. The low Q resonances cover a much wider bandwidth.

My thinking is while a localized response difference changes only a small range, a tilt works to make it more noticeable over a much wider range. I'm probably talking out my rear here.

Look at the filter banks and remember they relate somewhat to how much one band masks another. (also note the masking band isn't the same as these filters, they tend to stretch to the higher frequency side of things). If you boosted just the region of one filter bank it might effect it and the two adjacent ones. However a small tilt will actually change your masking levels over the entire bandwidth. It seems we are pretty sensitive about that. Again not my field and maybe you shouldn't listen to me.

1588225280647.png
 
March Audio said:
Here is a clip of white noise (not representative of music but shown to demonstrate the point) with a section filtered to be 0.5dB down at 20kHz. Its plain as day. Interestingly I find the change to the filtered section when it starts is less noticeable than when it ends.
Click to expand...

Could this be the (increasing) phase shift you are perceiving?
Since you mention a clearer experience through headphones.

from Dr Floyd Toole:
" It turns out that, within very generous tolerances, humans are insensitive to phase shifts. Under carefully contrived circumstances, special signals auditioned in anechoic conditions, or through headphones, people have heard slight differences. However, even these limited results have failed to provide clear evidence of a 'preference' for a lack of phase shift. When auditioned in real rooms, these differences disappear.. ."

(excerpt from https://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2)
 
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Denman said:
Could this be the (increasing) phase shift you are perceiving?
Since you mention a clearer experience through headphones.

from Dr Floyd Toole:
" It turns out that, within very generous tolerances, humans are insensitive to phase shifts. Under carefully contrived circumstances, special signals auditioned in anechoic conditions, or through headphones, people have heard slight differences. However, even these limited results have failed to provide clear evidence of a 'preference' for a lack of phase shift. When auditioned in real rooms, these differences disappear.. ."

(excerpt from https://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2)
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I think its very unlikely.
 
Good morning everyone. At least this side of the pont. After reading and reading and asking recommendations, and again reading all technical answers and questions and answers on answers from very respected people and become in doubt again ... cause, when I am almost sure there is no audible difference, someone respected, highly manufacturer comes with explanation why there could be may be a difference.
SO I took this morning a decision on recommendations from some members here.
I bought myself a second hand quad elite qsp, send him straight to Quad Revision in the Netherlands, they will replace everything with good stuff, thats what they say, don’t know what exacly I am not an engineer, they were speaking of mundorf, it means nothing to me, there must be some trust, the amplifier will be new inside outside, full waranty, so the amplifier will be future proof. And if a problem ever happen, any audio tech man could work on it.
So in the same philosophy as my speakers Harbeth 30.2 I have now a poweramp.

Cause I live in Europe it’s nearly impossible to send this amp for measurements.
So if someone got a quad qsp could you send it to Amir for measurements Pls?

So next question Dac streamer volume control, but will start new thread in streamer Dac threads.

thx to everyone for taking time to help me.
 
March Audio said:
Its not a boost or cut at a specific frequency thats audible, its a tilt in frequency response - change over a range of frequencies. It will depend also on the spectral content of the music you are listening too and of course your hearing.
Click to expand...

IMHO hearing such small differences works better with pink noise than with music. :D
 
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