booster for double bass with piezo pickup

[michal_k]

hello,

I'm looking for a layout for a clean boost with input impedance of 10M, i found a markm layout of these:

http://www.aronnelson.com/gallery/v/MarkMs-Gallery/album15/album76/MosfetBooster_LAYOUT.gif.html

but I'm not shure of it's impedance and all that small value caps.

advice me something please

[jaytee]

It will boost, and give you 1M input impedance if you omit R1.

[Processaurus]

It will boost, and give you 1M input impedance if you omit R1.

10M impedance if you omit R1 (a pulldown resistor to prevent switch popping, which you wouldn't have because it would be on all the time as a preamp).  Should work just fine.  Good choice going for a super high impedance preamp, I hear that if impedance is too low with the device a piezo feeds it will lose low end, the opposite of what happens with magnetic pickups.

I wonder if regular garden variety piezos will work as pickups if you stick em down right?

[michal_k]

yes, but you must shield them carefoully cause they tend to hum.

i think you may find this one helpful:
http://www.talkbass.com/forum/archive/index.php/t-176956.html
http://www.talkbass.com/forum/showthread.php?t=212443&page=5

[jaytee]

Oops I meant 10M soz. You could raise R2 to 20M, maybe try both see how it sounds. The preamp needs to be as close as poss to the pickup if you want to cut down hum.

[frokost]

The MOSFET booster is great for piezo pickups, or at least that's what I thought when I saw this (http://www.muzique.com/news/index.php/?p=23) page 

Luckily it was true. I've built a booster with a crude switchable diode clamp at the input to prevent voltage spikes from the pickup, and it works beautifully. We use this for a violin, and we are now able to have two fuzz guitars and full racket from the drums while we still can hear the violin clearly at rehearsal. We run it through a clean amp with a huge mids scoop. Sounds really good. The input impedance of the booster is indeed 10M, and there is no problem picking up bass frequencies with it. I had fun amplifying my heart with it 

[michal_k]

yeah, it seems that mosfet booster is the best choice for my needs. frokost, did you use any of the existing layouts/PCBs ?

[frokost]

Ordered the PCB from muzique.com, for once. Since this was kind of important and the first build that wasn't meant for myself I thought I should do it as proper as possible. There are a few differences between that and the one featured in markm's layout, but it probably doesn't matter that much. The most important thing, as I understand it, is the high input impedance, as explained in the article I linked to. The piezo itself will probably have a larger impact on the sound than the preamp as long as the input impedance is high. Not to mention where you mount it.