Replies to This Discussion

Permalink Reply by BrianQ. on December 5, 2018 at 7:12am

You’ll have to run the piezos through an onboard preamp, series has more output though? FYI, the Fender powerstrat has a similar configuration,good luck

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Permalink Reply by Tom T on December 8, 2018 at 1:13pm

I read somewhere (maybe on this site) that the Piezo has such high impedence that is has trouble impedence matching with most amps. One way to lower this impedence is to put Piezos in parallel. I've tried this and there does seem to be less amp hum without loss of volume. Therefore, I say parallel.

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Permalink Reply by Paul Craig on December 16, 2018 at 7:08am

Tom is right. Wiring in series just magnify's an already bad problem with the impedance.

Multiple piezo's should be done in parallel.

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Permalink Reply by Bryan Pieper on January 13, 2019 at 9:12pm

Yep. Wiring in series increases impedance, which is already an issue with piezos. Wiring piezos in parallel reduces impedance, which is good, but I have heard it also causes a loss of signal, which is bad if you are trying to get the piezos to match the signal strength of the humbucker. I think the only way to get a piezo and magnetic pickup to play nice with each other is to run the piezo through a buffer/preamp, whether for impedance matching, signal boost, or both.

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Permalink Reply by Paul Craig on January 14, 2019 at 8:13am

The more expensive acoustic preamps have hookups for piezo and magnetic pickups and they add a buffer to the piezo while equaling the impedance mismatch. They can go for several hundred dollars.

I have a git with a humbucker and a piezo wired to separate pots(500k HB & 1meg piezo) and a 3-way switch. It works okay.

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Permalink Reply by Cause the Blue rat on December 22, 2018 at 9:46pm

Think of it this way. Series doubles the impedance. Parallel divides it in half. Unfortunately you may not get the same output between the pickup and the piezos. Could turn the pickup volume down a bit to make up for the difference. Let your amp work harder to get the over all volume level you need. 

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Permalink Reply by Martin Simpson on December 26, 2018 at 3:50am

After thinking about this alot and reading the generous advice above, I decided to build a simple test jig.

 I hot glued four jumbo piezo disks to the inside lid of a cigar box. I put them in a square configuration right in the center of the lid. I took two of the piezos that were diagonally across from each other and wired them in series. Then I took the other two piezos that were also diagonally across from each other and wired them in parallel.

 Next I put an output jack and a SPDT switch in the side of the box so that I could swap instantly between series and parallel.

 Then I plugged it into an amp and started tapping on the box.

 As with most things in life, the sound output was a compromise...

The series setting does give more output volume. Maybe 10 or 15 percent more, but it also picks up more hum from flourescent lamps. The sound in the series setting is also fuller compared to the parallel setting. In the parallel setting some of the lower frequency sound rolls off, but the hum is noticeably less.

 Since this is going into a resophonic style guitar, I think I'll go with the parallel wiring in order to get a sharper, more jangly tone.

I'll let you all know how it comes out.

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Permalink Reply by Paul Craig on December 26, 2018 at 10:08am

The series wiring could be a good thing to have with low output volume amps as long as you use a lot of box shielding and enough insulators between the piezo's and box. Solid body gits might work better with that type of wiring.

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Permalink Reply by Tom T on January 14, 2019 at 1:13am

An excellent approach to a common question. Your experiment should be helpful to a lot of folks.

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Permalink Reply by Rob Todd on February 11, 2019 at 6:57am

I am just about to put two piezos in my latest build and found your research invaluable. Many thanks.

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Permalink Reply by Bryan Pieper on January 13, 2019 at 9:19pm

Very cool that you did that experiment. I would love to do more of that sort of thing, mixing and matching 100 combos of pickups to see what happens, but I already have too little time for building without venturing too far off the beaten path.

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Permalink Reply by Martin Simpson on January 17, 2019 at 2:27am

Now that the build is finished, I have the answer to my own question.

The dual piezos wired in parallel are actually louder than the humbucker! If I run the humbucker at full volume, the piezos have to be set at about 2/3 to 3/4 volume to match.

Ill get picures up ASAP.

By the way they sound great. Thanks for all the advice.

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