I seem to remember testing these when you brought it up last month and they were completely fine on my system. No distortion, whatsoever.

Did you check to see if you had the volume boost enabled in the options? I think it doesn't do anything on certain board revisions, but still worth checking. Did you contact ikari regarding a possible bug in the latest firmware for the new FPGA?

EDIT: Nevermind. I see you did both of those things, already. The fact that this doesn't happen on my set up, and neither does it on ikari's, it's either down to your cartridge having a bad amp or it's a part of your own signal chain. Apart from maybe being a little louder than they should be, there's nothing "wrong" with the PCM files.

i did contact ikari's people on github. so i am a bit back and forth now

yes, they are checking it as well. and i will pass over the point with the amp. what revision of the fx pak pro are you using?

i have no issues in tnmnt turtles in time, final fight, biometal.. but star fox in the other hand also makes trouble.

The amp is purely speculation, as I have no technical knowledge of the workings of it where an SD2SNES is concerned, but it seems like it's sensitive to higher amplitudes.

I have an SD2SNES version of the Pro. It'd be one of the first run Pro's that wouldn't fit into a US cartridge shell, as I got it when it was originally announced.

and any suggestions how i would check the amp and the signal chain?

i thought - from my perspective - i checked what i would understand as signal chain. by using different snes, different cables, different connection-variants and different tvs. but maybe i should understand something else under "signal chain"?

No, you got it. If you still have the problem after alternating and eliminating other sources and paths from the SNES to your audio system or TV, then your understanding of it is fine.

@relikk

uff, at least i got this right

but any suggestions how i could check the bad amp, to pin point that problem?

I'm afraid not. Only ikari can help you with that, if it is indeed the issue.