Looking for DIY onboard piezo bass preamp

[anotherjim]

You still need the individual caps into the pots. If nothing else, the DC current into the pots without the caps is a waste of battery capacity.

[theehman]

I really appreciate all your help!  I added the caps back in front of the trimpots and left the capacitor on the input of IC2-A.  I think this should do the trick. I'll get my PCBs ordered and let you know how it works out.

[iainpunk]

You still need the individual caps into the pots. If nothing else, the DC current into the pots without the caps is a waste of battery capacity.

well. the TL07x series does suffer from crossover distortion and the DC load would relieve that problem altogether, at a trade-off to battery life of course, but i strongly believe its worth it, if its something you hear and are bothered by.

i think this one is better:

Thanks for the input, guys!  Here's my updated schematic with your suggestions.

and maybe add a 10k resistor between the outputs and grounds of the other two opamps as well.

BUT ONLY IF YOU HEAR THE CROSSOVER, not everyone seems to hear the crossover distortion... if you don't, ignore my post

cheers, Iain

[theehman]

Got my PCBs last week and all the parts I didn't already have.  I put it together over the weekend and installed it today and it works great!!  I'll post some pics of the finished preamp installed when I get a chance. 

Btw, if anyone else needs a 4-channel piezo preamp, I have several extra PCBs available.  I had to order 5 and I doubt I'll ever need more than 2 (keeping a spare for another project).

[theehman]

Pics as promised.  I made these with an area for a 9v battery holder but it was too tall to fit in my bass.  Easily removed if needed to make the pcb smaller.

[iainpunk]

that PCB looks nice, as does the bass. that colour is perfect for that model!

''no thanks to zeta''
who is zeta and what is the context?

cheers, Iain

[theehman]

Zeta is the original manufacturer of the bass.  I think they just do violins now.  I contacted them about getting a a schematic for the preamp and they were somewhat non-helpful.