Hex Piezo pickup - Preamp?

[Jaicen_solo]

Anybody have any ideas for the best piezo pickup pre-amp design?

My pickup has six individual elements, which I want to sum together, and output through a TMB tone control.

Can I just put something like a 10k trimmer in line with the output of each pickup and route them through to a high impedance op-amp buffer, or do I need to buffer each element individually?

[~arph]

I'm watching this. I got ghost saddles and my preamp died, bit expensive to replace

[GibsonGM]

Anybody have any ideas for the best piezo pickup pre-amp design?

My pickup has six individual elements, which I want to sum together, and output through a TMB tone control.

Can I just put something like a 10k trimmer in line with the output of each pickup and route them through to a high impedance op-amp buffer, or do I need to buffer each element individually?

Seems like that would be a good way to do it - classic opamp mixer...then you can adjust each trimmer for equal volume on each string, of course. You should have good input impedance this way - I don't see why this wouldn't work.   

Why don't you try out 2 or 3 strings, on the breadboard, just to see how it sounds?

[Gurner]

Can I just put something like a 10k trimmer in line with the output of each pickup and route them through to a high impedance op-amp buffer, or do I need to buffer each element individually?

Hex pickups normally are quite low impedance ...you might get away with a standard opamp amp configured as a summing amp....

http://www.circuitstoday.com/wp-content/uploads/2011/11/summing-amplifier-circuit.png

but if not, what you're proposing is not (IMHO) the optimum way to approach it, .... bin the idea of a trimmer on the input of a high impedance buffer, but have a high impedance buffer for each pickup output followed by a summing amplifier ....this is where your trimmer would come into play.

[enrique]

i design this, to replace the original parker p38 piezo and magnetic preamp work really good and pretty close .
http://www.rcustomspedals.blogspot.com/2012/09/pre-onboard-para-microfonos-magneticos.html

[ashcat_lt]

Remember that piezo elements are capacitive whereas magnetic pickups are mostly inductive.  They both want high impedance loads, but for opposite reasons.  A "loaded down" magnetic pickup loses treble.  A piezo connected to a too-low Z input loses bass.

Also, I cant see any good point in having a hex pickup if you're not going to have access to the individual strings.

I think you should have six individual buffers (jfet or opamp) with individual outputs which come before your summing stage.  The standard inverting summing stage will not likely give you a high enough in-Z by itself.

[Gurner]

Hex pickups normally are quite low impedance ...you might get away with a standard opamp amp configured as a summing amp....

Earlier I read hex pickups, and a Roland GK2 midi pickup instantly sprang into my head, but just seen you've a piezo hex ...... so scratch the above! (I've no reason to have missed that, you splattered piezo in the title & opening post!)

[GibsonGM]

Like I said, try building a summing amplifier, and see what 2 of them sound like.  If they need buffers, you'll know pretty quickly, and will have 2 of the summing amp inputs ready to go!

[ashcat_lt]

Like I said, try building a summing amplifier, and see what 2 of them sound like.  If they need buffers, you'll know pretty quickly, and will have 2 of the summing amp inputs ready to go!

Yes, but try the two low strings, or maybe both Es

[pinkjimiphoton]

guys,
i have a related question.

do you HAVE to use a preamp with these things?

i wanna put a schaller piezo tuneomatic on the semi hollowbody i'm building (or the 12 string neck of my doubleneck) but i am a FUZZFACE ADDICT (PINK:"HI, I'M JIMI AND I'M A FUZZAHOLIC"....DIY STOMPBOXES: "HELLO, PINK")..

and any kinda buffer before a fuzzface just ruins the interaction of the guitar and fuzz.
the only other thing i could think of would be to put it on a switch, so i could still have the passive output (or maybe give it a dedicated output jack?)

sorry to hijack the thread, but i'm curious what you guys think.

[ashcat_lt]

Jimi, I think your answer is in my post above.  One of the big things about an FF is the way its low-Z input loads down the (inductive) magnetic pickups.  It'll do pretty much the opposite with the (capacitive) piezos.  You'd be better off with a good buffer followed by one of those (inductive) pickup sim circuits.

[pinkjimiphoton]

thanks ashcat..
seems to me then, maybe my best bet is to keep the two signal paths completely discrete.
while i could wire the bridge as a hex, i'm gonna keep it summed to mono just to make life easier.
you DID answer my questions... thank you!!

[ashcat_lt]

Pas de problem.  If you was gonna mix the mag with the piezo you would want to buffer each separately first.  Keeping them separate is probably your best bet.

[tempus]

Not exactly what you were asking, but I use Ghost saddles on my electric guitar so I can switch from an electric to acoustic sound mid-song. I built this onboard buffer and it works great (no amplification or tone stack though):



The 10uF cap can probably be lowered, and I think I later added a 10M resistor to ground between the 22K resistor and the input to the JFET.

Try it out - a buffer may be all you need with all the EQ on most amps/mixers.

[Gus]

http://www.diystompboxes.com/smfforum/index.php?topic=93625.0

http://www.diystompboxes.com/smfforum/index.php?topic=92274.0

[Jaicen_solo]

Quick resurrection for some clarification about this again.

Firstly, do I need individual buffers for each element if i'm going to sum them to a mono signal?

Secondly, it's going into the guitar, so obviously I want to keep current draw low, but I want low noise. A couple of TL062's will be ok in terms of current draw, but what's the noise like compared to say, a J201?? I want to have a small amount of gain, followed by a low impedance buffered tonestack.