OT - Onboard opamp preamp Q

[T-Man]

I'm planning on putting an opamp based preamp in my bass and have a question.  

I will be buffering each pickup individualy, with a unity gain opamp, each of these will be followed by a volume pot connected to ground, with the wipers to the output.

Should i put a third opamp between the volume controls and the output? the pots would load the signal, no?

i should know this... i am an EE student...  :oops:

thanks.

Tristan

p.s. this is my new favorite forum.

[casey]

im going to send you a private message here in a second,
with a nice preamp for your bass....

it's coming to ya in about 10 minutes...

[casey]

you've got mail....check your pm.

[casey]

i sent you a 2nd installment......

let me know if you got the 1st email....it was pretty big...

[ejbasses]

Hi!

Nice to see a fellow bassist around here.

I put an on board pre in my bass too. Nothing fancy its just a single stage class A jfet circuit with a switchable lopass filter and series/parallel switching on the pickups.

Hey casey can you send me that preamp schematic too??

thanks

[casey]

Hi!

Nice to see a fellow bassist around here.

I put an on board pre in my bass too. Nothing fancy its just a single stage class A jfet circuit with a switchable lopass filter and series/parallel switching on the pickups.

Hey casey can you send me that preamp schematic too??

thanks

yeah, ill pm you for your email address.....

[T-Man]

Casey, thank you for the schematics, they are interesting, however they look like preamps intended for AMP use... I am making an onboard preamp.

In addition, I have more or less decided how I am going to do this and would like an answer to my question... i am inquisitive and stubborn. :wink:

thx
T-Man

[casey]

the 3rd one i sent to you (2nd email) should do the trick.....

sorry i couldnt be of any help....maybe you can use them later.

[Tim Escobedo]

A summing node into a op amp would probably be the legit way of mixing the two pickups (if that's what you're asking). However, of both pickups are indeed buffered with same output levels and impedances, you could probably get away with a simple passive summing circuit.

[T-Man]

tim, that's the kind of answer i was looking for.  thank you.

i think i will put in a third opamp... can't hurt, right?

thanks all

[lovekraft0]

Have you seen Albert Kreuzer's onboard bass preamp? If you're not comfortable with JFETs, it should be easy enough to do with opamps.

[T-Man]

thanks lovekraft, i think i am going to do what i planned, but maybe i will try that in my other bass...

[cd]

Should i put a third opamp between the volume controls and the output? the pots would load the signal, no?

Technically yes, but if the rest of your circuit is designed properly, it won't make any sonic difference (one that you can hear).  Unless you want to add gain with the third op-amp stage, I wouldn't bother.