Do all amplifiers sound the same? Level matched listening test

[Ashl777]

I understand room will have an effect but it will be a constant one. If the ambient noise can be eliminated it will still produce a plot with a real speaker load(not an emulating one)that can be compared to the loopback

 

[pma]

As @antcollinet has already said, it is impossible to get properly matched recordings even from the same system, with a microphone. Instability of air path, reflections, microphone position instability etc. masks the real differences. The only way is to record electrical signal from amp outputs when they are loaded with real speakers. I did such tests with the same result as in this thread. The only amps distinguishable in a DBT test were class D with frequency response deviations due to complex speaker impedance. Namely it was AIYIMA A07. The class D designs with LC filter outside FB loop are intrinsically flawed.

 

[jEDGEc0m]

I understand room will have an effect but it will be a constant one. If the ambient noise can be eliminated it will still produce a plot with a real speaker load(not an emulating one)that can be compared to the loopback

I recently swapped from load dependant Class D amp (Fosi V3 Stereo) to one with PFFB (2x Fosi V3 mono).
With umik-1 microphone, one of the first things I did while setting up, for a laugh, was measure in nearfield with one amp, then the other - (mic ~200mm from speaker).
See if there was a crudely measurable difference in Freq response.

Screenshot of difference at the end of this post on another thread...

Post in thread 'Fosi v3 Mono - User Impressions | Owner's Thread'

Sep 9, 2025

TLDR: I received 2x Fosi V3 mono with 2x 48V 5A.
Their phase is correct. they have 19-25dB gain switch on RCA. They have only 1 QC sticker.
They don't make any concerning amount of noise when turned on and off, even yanking or plugging in at mains with switch on amps set to "On".
They are not disturbingly warm after a few hours use at moderate volume, though the room is pretty cold at present.

They work. Music is being amplified and sounds as such. success! but it's only been mere hours.



I just received a pair of Fosi V3 Mono today, with 2x 48v 5A power supplies. (Previously...

• jEDGEc0m

• 

Even if there weren't some mic-measurement-based variations, I reckon that difference would be pretty subtle to hear with actual music content. Perhaps audible with pink noise and quick A-B switching...

(ps Where the graph is above the 0dB, that is indicating more output at that frequency with the Fosi V3 Stereo)

 

[pma]

It depends, strongly, on the speaker used, on its complex impedance, how it affects the usual 10uH/1uF output LC filter resonant frequency response at high frequencies. Speakers with prevailing capacitive impedance at highs are worst in this regard. The second amp has to be really load invariant one, like Purifi or linear amp (class A, AB). Even the TPA32XX with PFFB based amps are not load invariant.