Questions regarding installation and operation of Piezo bridge

[seang15]

Greetings,

I saw some threads on this, but nothing specifically geared toward what I am doing, and/or the specific questions I have here.

I bought one of the piezo-equipped bridges on Flea-Bay recently. It's a nice, high-mass bridge, very sturdy and seems great for the money. ($50 shipped for a gold bridge with piezos!) Of course, many people say 50 bucks is too good to be true for a high-mass, gold, piezo-equipped bridge. I beg to differ, but I also understand I have some work to do if I intend to make it work properly, or at all. And perhaps I can benefit others that have made this purchase, by fleshing out, as best I can, what I am doing (or trying to do)...and I don't think it's all that unusual or different from what others may want to do, as well.

First off, the two wires hanging off the bridge: You guys think (or those with experience, know) that these are for the input jack? Or one to input, and the other to ground perhaps? Would it make sense to drill another separate hole for the piezo input jack, separating the two systems completely? (I am about finished with my project fretless bass, so I can do a bit of drilling as part of the finishing touches.) Or, do you folks prefer it integrated with the other components (typical "magnetic" pickups)? I don't mind it separated and isolated from the regular pups system, as I want that "upright" sound that piezo may provide. (I have, and love, my upright...I know there is no other way to get an "upright" sound, but electric with piezo is a decent stand-in for it!) Or at the very least, an acoustic bass guitar sound.

OK, I know it says it needs a preamp to operate, makes perfect sense. (BTW, I am planning to utilize this preamp: BEQ12-34PTAP (Bass mods). Some quick searching of threads and Googling, found some other information as well (and perhaps some other needed components to make piezo work on an electric bass): For instance, the notion of a buffer amp, whether on-board or external.

For instance, this one: http://www.scotthelmke.com/Mint-box-buffer.html

Is this (or similar) absolutely necessary for the piezo to work? Should this, along with the preamp drive the piezo bridge, or one or the other? I read that the biggest need is the change in impedance, i.e. I need an input of 10ohms, instead of the lower impedance of nearly all bass amps. I have an Fdeck High Pass Filter for this, love it for upright. Seems like the piezo bridge pup holds the same principal as my piezo in the upright world, except the upright has more volume, as it's an acoustic instrument, vs. a slab in the electric bass world.

So, to sum-up (and thanks for reading to this point!):

With my half-assed knowledge of this stuff thus far, I am thinking it's an either/or:

EITHER: (Option #1):

Wired to the preamp and existing input jack (Note: Where to solder the (2) wires?)

OR: (Option #2):

Put in separate input jack. wire-in the buffer amp. FDeck (external) HPF (10 ohm input). External preamp made for acoustic instruments. (Fishman, etc.). So this time: (Internal): Buffer Amp to Input Jack (External): Fdeck HPF, acoustic instrument preamp, to amp. (Note; where to put the (2) wires from bridge?

Thanks in advance! I know this is quite a bit, and I was confusing the heck out of myself here, I likely did same to you. My apologies if this is the case.

And the likely best solution may be different than what I have above, or some culmination of all the above, I do realize this too.

Thanks again!

Sean

[1bassleft]

Hi, it's really late here and I have to work so this is a bit quick but;

I bought one of those bridges off fleab for a long-stalled build. I got talking to an unrelated ebayer on there called dh.designs (exactly as I've typed it). He's in CA, near Disneyland and I made it clear that I wasn't buying off him (he had a piezo + 2x mag bass with a heap of switches) but asked him some Qs.

He gave hours of time, messaging me back and forth, suggesting the EMG PB3 sold by Bitterroot (but not outside US - I ended up getting a Wahburn/Parker Powerchip pretty cheap on fleab -still available) which is just a simple + cheap buffer which would allow any option you like.

The main point is, dh.design was a super-helpful and very generous communicator for no gain to himself. I can perhaps copy our comms over to you if you PM me and you can read through. Or maybe you could try messaging him yourself; he knows me as "Oz" and I only stopped comming with him because of a Christmas vacation and, since, I've been busy with other stuff.

[seang15]

Thanks for the reply! Great info, I will PM you, thanks again.

[seang15]

El bumparooney....

[mrbell321]

I'm having trouble following your options, so I'll just tell you what I think:
Piezo's two wires go to 2 inputs on the preamp(or, alternatively, one goes to ground, 1 goes to preamp input and preamp also has ground wire).
Preamp out goes to the input jack. Or preamp goes to volume control which goes to jack. Or preamp goes to tone control which goes to volume which goes to jack. Depends on what is handled as internal to the preamp, or post preamp and what controls you want on the bass.

If you're using that circuit you linked to, it would be the:
Piezo->tone->volume->jack


Now, on that circuit, he has a switched labeled "gain". That's not a gain switch. That's an input attenuation switch, which means it will lower the input signal, but not the noise generated by the circuit, resulting in a poorer signal-noise ratio. It does not change the gain of the rest of the circuit. There are better gain control schemes, I think.

[walterw]

that bridge needs to go straight to a dedicated piezo pre first (and it needs 10MΩ, not "10Ω" to get all the low end).

once that's done, the pre's output will be just like any other active preamp.

the fishman powerchip will work just fine to blend the buffered piezo into the buffered magnetics; i think bartolini makes piezo buffer/blender pres as well.

(piezos won't mix with magnetics without these preamps in between; you'd be wiring capacitors parallel with inductors, they'd wreck each other's outputs.)

[seang15]

Thanks folks, for the replies. I will look into all this asap. Much appreciated.

Thanks,
Sean