PAIA synth drum q's

[nss at hevanet.com]

Hello all, 
I made up a pc board based on the synth drum section of PAIA's analog
drum board. I followed the instructions on how to adapt it for bi-polar
power supply operation(as opposed to +12,+5 as normal.) It works, but
sounds a leeetle funny. it has a pronounced "pop" at the begining, and
when you take C1 out of the circuit, as the web page says you might want
as an option, it  just makes a pop. It is assembled correctly and
running off +/-15v. I'm using a tl072. I don't know what the kit comes
with.
	Could somone familiar with this kind of thing take a peek, and tell me
if there would be any other mods suggested on top of what they say to
convert to bi-polar?
	Anyone have experience with this circuit?
I would have bought their kit, but I have most of the sounds besides
this one. I'm not quite sure what it's suposed to sound like, it sounds
similar to what I would expect however.

http://www.paia.com/syndrum.htm

Thanks for any thoughts or help!!

-Al Fisher