How do i lower a Piezo pup signal going into preamp?

JtheJazzMan · #1 02-05-2009, 02:38 AM

Just as the title says, i have a magnetic pickup and piezo pickup being blended by a preamp on the bass but the piezo is overpowering the preamp and causes some distortion. can i add something small onto the wire to lower the piezo volume? resistors or something? (electronics newbie here)

**Francois Blais** · #2 02-05-2009, 04:43 AM

What preamp is it?

Jornan · #3 02-05-2009, 04:50 AM

It depends on the bass, but I know that you can adjust the piezo on MM basses by turning a small knob (or something like that) on the back of the bass (where you have all the covers for electronics and so on). Sure you don't have a volum knob for piezo volum?

Hope my English is understandable

Roger Davis · #4 02-05-2009, 05:19 AM

I assume that the preamp is 'on board' - ie on the front of the main amp in the same unit. Then try something outboard, eg a Fishman Pro eq which is the Platinum Pro's little brother.

**Francois Blais** · #5 02-05-2009, 06:43 AM

MM Basses?
Aren't we discussing double bass here?

Jornan · #6 02-05-2009, 07:03 AM

Sorry. Saw this on the TB frontpage and didn't see that it was in the double bass forum

JtheJazzMan · #7 02-05-2009, 02:50 PM

Its a biesele preamp, with his mag pickup in 1 input and a fishman full circle in the other.

when the blend is set to full piezo its a fair bit louder than when set to fully magnetic, and when you hit the e string hard, theres some distortion.

this happens regardless of where the volume knob is set, it just means the distortion is quieter, but still there. so im under the impression i need to lower the signal going into the unit

robgrow · #8 02-05-2009, 06:36 PM

Have you checked the 9 volt battery? If it's not the battery, I'd contact the manufacturer directly. The preamp should be able to deal with the signal from the Full Circle without distortion.

Rockman · #9 02-05-2009, 06:48 PM

You also may want to look into a high-pass filter for the piezo. I had that problem a lot, it wasn't necessarily the loudness that caused clippage, just the lowness that the piezo pickup.

fdeck · #10 02-05-2009, 07:53 PM

Just a note, even though I know this is a DB question. If a piezo pickup needs to be padded, I have formed the opinion that the correct way is with a capacitor in parallel with the pickup. Unless you know the capacitance of the pickup itself, choosing the best capacitor value is a matter of trial and error, starting with values around 0.001 to 0.01 microfarads.

JtheJazzMan · #11 02-06-2009, 08:30 PM

big thanks to everyone, especially fdeck.

a 3.3 nF capacitor works a treat, really helps to match up the 2 pickup signals, and the distortion from the piezo is gone too

just put an RCA T-adapter into the fishman RCA and encased the capacitors in small RCA connector heads so ive got a bunch of easily transferrable capacitors between 1 - 10 nF