Looks like its a month since this has been posted, so i hope a solution has been found..
But i have the exact same problem with my sammichSID.. Everything works great but the filters are not really responding .. they make a bit of noise and little things happen.. but its totally not like the audio examples in the manual or like any other filter on any of my synths .. so something is definitely wrong..
Every voltage test checked out and the OS installed fine and well its all fine and rainbows except the filter part :/ ..
Im using two 6581 SIDs. And one is from an old HardSID card i had so im very sure at least one of them is working perfectly. So i dont think its a problem with the SID chips.
Could it be something with the C1L, C1R, C2L, C2R thingys? i used the 470pF (6581), but does it matter what holes i put them in?..
well hope someone can help :)