Piezos TRansducers in a Semi Acoustic

barnsleyboy · June 2023

I've got a cheap Amazon contact piezo transducer that I'm thinking of mounting in my HB-35 semi acoustic so I can thump the body a bit to get those percussive drum sounds like that ginger guy*.

https://www.amazon.co.uk/Mr-Power-Transducer-Acoustic-Mandolin-Accessories/dp/B07WLXM15F/ref=sr_1_18?crid=24THUWICETPCI&keywords=acoustic+guitar+pickups&qid=1687776448&sprefix=acoustic+guitar+pickups,aps,79&sr=8-18

There are 3 seperate ones connected to a jack socket, so my idea is to spread them out around the body to try to capture different frequencies of thumping. Layout would be something like this:

https://flic.kr/p/2oHWin8

I'm thinking of just having one tone control and converting the other to a volume control for the transducers wired directly to the main jack socket. Has anyone had any success doing this? Should I use epoxy to fix the little blighters in the guitar?

I suspect that I'm going to have some issues with the output being tiny compared to the humbuckers, so I may have to incorporate a tiny pre-amp. If I have to do this, has anyone got any recommendations for something cheap & useable? I really only want to capture the drumming sounds, not get a pristine acoustic guitar sound.

* I think he's called Ned Sherin or something like that!

ICBM · June 2023

I would connect them to the jack directly, no volume pot, and use an external pedal to boost and control the volume. If you use a stereo (TRS) jack and connect the piezos to the ring terminal, then use a splitter cable, you can do it all from the outside while leaving the guitar effectively completely unmodified if you want to just plug a normal mono cable in.

I would use superglue to stick them on, but epoxy will work too and may be easier to work with since it has a longer setting time. You can clamp them in place while it sets using some bits of soft wood the right size to wedge between the guitar back and the pickup.

barnsleyboy · June 2023

ICBM said:

I would connect them to the jack directly, no volume pot,

I'm really thinking that the volume pot would be the on/off control for the piezo's rather than something that I would dial in the sound with. I'm not a great one to tweak around with tone pots, so just having one to control both pickups wouldn't be a loss for me.

The piezos are self adhesive using supplied double sided tape, so I might try that before I commit to epoxy/ superglue. I think gluing would give me a better contact with the wood and allow more sound transmission.

ICBM · June 2023

barnsleyboy said:

I'm really thinking that the volume pot would be the on/off control for the piezo's rather than something that I would dial in the sound with.

It’s more that a pot will kill the bottom end from the piezos to some extent - any lower load impedance than about 10M does - which may not be ideal if you want ‘thump’ percussion sounds. You may be better with a switch if you want to be able to turn them off.

DartmoorHedgehog · June 2023

I did something similar with an even cheaper piezo pickup. It was a cheap clip-on pickup intended for violin, just a single disc. I just superglued the disc to the underneath of the bridge plate and wired it to an endpin jack socket. Considering it was such a cheap pickup I'm impressed by how good a sound I get (with an external preamp pedal or directly into my audio interface preamp). It's very bright but once EQed it sounds fine. Makes me wonder whether I should invest in a slightly better multi-transducer pickup.

I've used it live a few times doing an acoustic set with cut-down band and sound engineers hate it - apparently it's a much hotter signal than they expect from the usual under-saddle setups and is a bit hard to control feedback, so might be worth bearing in mind if you're going to use it live (although the pickup did cost me £3 so I can't really moan!)

barnsleyboy · June 2023

ICBM said:

barnsleyboy said:

I'm really thinking that the volume pot would be the on/off control for the piezo's rather than something that I would dial in the sound with.

It’s more that a pot will kill the bottom end from the piezos to some extent - any lower load impedance than about 10M does - which may not be ideal if you want ‘thump’ percussion sounds. You may be better with a switch if you want to be able to turn them off.

Good point @ICBM I've got an old push-pull pot knocking around that I could make use of to switch it in and out

DartmoorHedgehog said:

I did something similar with an even cheaper piezo pickup. It was a cheap clip-on pickup intended for violin, just a single disc. I just superglued the disc to the underneath of the bridge plate and wired it to an endpin jack socket. Considering it was such a cheap pickup I'm impressed by how good a sound I get (with an external preamp pedal or directly into my audio interface preamp). It's very bright but once EQed it sounds fine. Makes me wonder whether I should invest in a slightly better multi-transducer pickup.

I've used it live a few times doing an acoustic set with cut-down band and sound engineers hate it - apparently it's a much hotter signal than they expect from the usual under-saddle setups and is a bit hard to control feedback, so might be worth bearing in mind if you're going to use it live (although the pickup did cost me £3 so I can't really moan!)

I'm pleased to hear that this is a possible! I won't be using it live, so feedback shouldn't be a problem. In terms of the external pre-amp, it will be going into my Helix so I can set-up a snap shot to kick in a pre-amp block with a carefully tweaked noise gate to keep things under control. I'll report back on results.

As always, thanks for the wisdom and assistance!

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Piezos TRansducers in a Semi Acoustic

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