ICS64S with 6581, digi-samples almost silent

[misc]

Hi,

so far, i am very happy with this PCB, everything works perfect, there's just a little problem. When i start Ghostbusters, i can hardly hear the speech sample, every other sound is ok so far. I changed the sid, but the problem resists. 
I am a little confused, because the sid chip works flawless in another c64 i tried.
Anybody who has an idea ?

Thanks
Mike