UPGRADE: FOSI V3 MonoBlocks OpAmp Rolling That Actually Might Work?

[solderdude]

But you are wrong about extra capacitance having no effect on the measurement or signal or amps would have even smaller capacitors.

There’s absolutely a benefit in moderate listening and definitely for transient peaks especially for example Als Sprach Zarathustra can definitely drive this amp well into clipping if the listening position is at typical distance 10-12ft away with a 86dB speaker that dips into 2-3ohm territory

Would like to see some measurements for that.

Also. Improving the slew rate of the op amp will help with especially transients because that’s the bottleneck in the performance of the amp

No it won't. Simply because the output voltage of buffers (like used in this amp) is max 3v.
Gain for the TPA3255 is 12x (21.5dB) so at 53V supply voltage you can reach 50Vp so 4Vp is 2.8Vrms

For 40kHz @ 3Vrms output voltage a slew rate of 1V/μs is sufficient.
The well known OP(2)27 is 3V/μs and even the stock NE5532 is 9V/μs, the lowly TL071 is even 13V/μs.
That of even the 'slowest' audio op-amps is many times higher than 1V/μs so no... slew rate of the input buffer op-amp is not even remotely important in this amp at all.

Also show me an audio file which has >20kHz content anywhere near 0 dB FS.. and even for that a high slew-rate isn't even needed for the few V out and max a few times gain.
Besides... show me high-res audio files with substantial content <50kHz. All music recordings are low-pass filtered anyway so there is no need for any amp to reproduce 10kHz square-waves with perfect edges... simply because there is no music on this planet with those edges.
Square-wave test signals are handy in the design period of an amplifier and even for testing though.
That's where slew rate is shown (power bandwidth limiting).

The slew-rate of the entire amp in question is thus determined by the output filter and BW of the TPA3255 amp and not by the used op-amp unless one uses non-suitable op-amps like OP07 or the μA741 .

Does it matter for high gain (pre-)amplifiers (mic, MM/MC) sure it matters.
Does it matter for power amps that need to reach 50kHz with 40V output voltages ? sure... but low gain, low output voltages... no.