Twin Famicom has terrible Audio

[Bibin]

I just got a Twin Famicom. It's awesome in every way, and better than my regular Famicom...

...EXCEPT that when playing Gimmick!, all the DPCM bass notes sound muffled and peaked. Why does this sound so terrible? It sounds fine on my regular Famicom; what is different in the TF audio circuitry and is there an easy known modification to bring it back to an acceptable quality?

I have removed C205 as others have recommended, and it has helped the audio clarity in general but the muffled DPCM-bass still remains in Gimmick! while in other titles it is not an issue. I will try to get other Sunsoft games that use the same DPCM-bass technique and see if the effect remains.

I've recorded some example audio:
http://mikejmoffitt.com/mus/gimmick_compare.zip

Does anyone have any ideas?

[MaxWar]

Your regular Famicom sounds muffled it seems.  Mine here is very clean.

Anyway there definitely are some parasitic noises on your TF recording.

Cannot help explain why though.

I myself made an audio comparison between some different famicoms.

Heres the link if you missed the thread:
http://www.famicomworld.com/forum/index.php?topic=8630.0

[famifan]

firstly define 'muffled sound'

check frequency spectrum of sound and compare them

[Bibin]

Muffled may be the wrong choice of word... either way, the TF sounds much worse than my famicom, and that is what I need to fix. In the FC sample, the bass is clear, while in the TF sample it sounds distorted.