https://www.stereophile.com/content/two-new-ftc-rules
"Previously, manufacturers measured power by driving their amplifiers at 1kHz and raising the power until the THD+N reached 1%. Now they must ensure that that standard is met at all frequencies between 20Hz and 20kHz, with THD+N less than or...
That's not proof. Some understand class B and AB differently.
I will ask differently. What is the quiescent current of the output transistors ? Are the emitter resistors present ?
IVX, don't make excuses ;), distortion is distortion, whatever harmonics are affected. On diya I showed a graph with bypassed caps vs stock, the THD 20Hz difference was 20dB. Cosmos is built for measurement, all the little things count.
SE/UNBAL 1.7Vrms input range, input caps bybassed -> 2.4mA DC flows to the source V1 ( 1mA when input range is 10Vrms)
TI Application Report - Buffer Op Amp to ADC Circuit Collection...
Not only a higher capacitor value can help, but also the capacitor type and voltage rating.
SE measurements, THDvF, 96k 24b, 1.7Vrms range
Red trace - stock cap 220u/10v
Green trace - Jamicon 470u/10v
Orange trace - Hitano EXR 220u/16v
Blue trace - Nichicon 1000u/10v
I already wrote IVX on diyaudio about input capacitor distortion. He claimed that my capacitors are faulty and I should replace them with new 220u ones.
https://www.diyaudio.com/community/threads/cosmos-apu-a-notch-lna-70-to-outperform-apx555b-for-30-000.386001/post-7726875
I recommend replacing the 220u/10V capacitors with 470uF/16V (C1 C2 on my schematic). I personally use 1000u/16v, I get much better LF performance when using the SE input.