Which onboard piezo preamp?

[tomasz]

I'm thinking of adding a piezo element to a prototype build and was wondering if anybody has some experience mixing regular pickups & piezo output? I've read a few articles on preamps using JFETs vs opamps, but cannot clearly decide what to try for best results.

I'd appreciate if anybody could share some experience or a schematic that worked well. Or if there is a good ready unit that can be used and that worked well for you.

 

[39martind18]

I've added piezo bridges on three of my electrics, a Sheraton USA, Heritage H550, and a D'Angelico Excell SS. My best experience is using the Fishman Power chip- simple, great sounding and not exorbitant in the price department. The piezo volume control knob on these Gibson style 4- knob control is put in the tone control position for the bridge pickup, and the neck tone becomes a universal tone. Hope this helps!

 

[wabashslim]

If adding to a solidbody you can expect your attack & sustain characteristics to be like the solidbody electric, not like an acoustic. I did it to a Strat Plus & was a bit disappointed...well, more than a bit.

The piezo volume control knob on these Gibson style 4- knob control is put in the tone control position for the bridge pickup, and the neck tone becomes a universal tone. Hope this helps!

Did you send the Fishman to a separate output or mix it with the mag pickups? If so, how?

 

[Paul G.]

I've got a Fishman PowerChip I will be installing in a Mahogany Tele I'm building now. It will be finished next week, and I'll let you know how it goes.

The Fishman mixes the signals when using a mono plug, allows separate outputs with a stereo jack and Y-cord.

 

[39martind18]

I've got a Fishman PowerChip I will be installing in a Mahogany Tele I'm building now. It will be finished next week, and I'll let you know how it goes.

The Fishman mixes the signals when using a mono plug, allows separate outputs with a stereo jack and Y-cord.

yup! I use the mixing feature to get an acoustic-like zing and sparkle to my electric sound. It makes my minihum equipped electrics (almost all of them) sound incredible- at least to my ears!

 

[39martind18]

If adding to a solidbody you can expect your attack & sustain characteristics to be like the solidbody electric, not like an acoustic. I did it to a Strat Plus & was a bit disappointed...well, more than a bit.


Did you send the Fishman to a separate output or mix it with the mag pickups? If so, how?

It has a function where if you use a mono plug for the output

If adding to a solidbody you can expect your attack & sustain characteristics to be like the solidbody electric, not like an acoustic. I did it to a Strat Plus & was a bit disappointed...well, more than a bit.


Did you send the Fishman to a separate output or mix it with the mag pickups? If so, how?

What @Paulg said!

 

[Willie Johnson]

I was strumming my Starcaster semihollow unplugged this evening and wondered if a piezo would give me some acoustic-like tones that I could use on its own or blended in with the magnetic pickups. It would probably be a time consuming boondoggle, though the idea of using one of the tones as a volume for the piezo and the other as a master tone is a good one.

 

[39martind18]

If adding to a solidbody you can expect your attack & sustain characteristics to be like the solidbody electric, not like an acoustic. I did it to a Strat Plus & was a bit disappointed...well, more than a bit.


Did you send the Fishman to a separate output or mix it with the mag pickups? If so, how?

It has a function where if you use a mono plug for the output, the signals are mixed. If a TRS output plug is used the piezo and magnetic signals are split and can be sent to different amps or amp and PA. Makes for a very full sound!

 

[tomasz]

Thank you all for chiming in!

To give you all more context, the build is a solid body electric. I may be doing some chambering, but probably not enough to get any acoustic properties out of it.

Since it is an experimental prototype, I decided to use a piezo element in the neck, under the end of the fretboard. Considering another one around the first fret or headstock area, as this point seems to vibrate pretty well (works for headstock tuners). I may add a third one to the chamber, to be able to compare how those different points perform.

I was looking at those JFET amps, as they seem relatively easy to build and have a small footprint:
https://cigarboxnation.com/profiles/blogs/piezo-preamp-experiment
http://hackaweek.com/hacks/jfet-audio-preamp-with-piezo-guitar-pickup/

This one could be another rabbit hole:
https://www.sound-au.com/project202.htm

But I am also considering potentially available preamp/buffer modules.

@Paul G. , would love to hear some sound samples, once you install the fishmann!

 

[naveed211]

The guitar in my profile pic has a Fishman piezo system. Just a mono jack and with mini switches, one for on/off, one for piezo/mix/off.

Sounds pretty good. Won’t fool anyone into thinking it’s a pre-war Martin, but it does the job. A bit of EQ (not included on board) and of course reverb helps.

It does add a really cool twang and increased definition when I mix the tones, nothing else really sounds like it, so I use that as a secret weapon sometimes.

 

[bullfrogblues]

I installed a Ghost System in my Reverend Charger 290 to have some almost acoustic tones for the band I was in. I needed to change from acoustic to electric at the flip of a switch mid-song. In a band setting the tones were believable enough. I'm not sure I'd want to do a solo gig with it, but I really did enjoy playing with the piezo and preamp.

 

[39martind18]

The impetus for installing piezo bridges in my electrics came from my Nashville Power Tele. It had a Fishman piezo bridge installed, and gave me a lot of interesting sounds with the signals mixed, or sounded really huge "Y'ed" into amp and PA. The semi and hollow bodies add a fullness on the lower end that the piezo gives brightness and definition to the tone. It has become "my" sound.

 

[Freeman Keller]

I install various piezo transducers in acoustic - K&K, Fishman, Braggs... - and if the manufacturer offers a preamp matched to their pickup I use it. The K&K are sound board transducers and they usually have an external preamp or DI to match impedance to the input of the amp and to offer some signal conditioning. I leave the choice to the owner - I don't have a need to plug in my acoustics.

Several years ago I helped my son with a solid body guitar with two magnetic pickups and a six crystal piezo bridge. The mag pickups got normal 2V2T controls, the piezo got its own volume control. There were no active elements on board the guitar. The piezo was brought out as a separate output on a stereo jack, that way it could be run thru its own signal chain. We did not try mixing the signals - the impedances would have been seriously mismatched.

The little PCB gathers the six signals from the piezo crystals, the pot on the far right is the volume for the piezo.

I'll add one more comment about this guitar. It was supposed to be the "every sound" guitar - two humbuckers with coil split and series/parallel connection plus the "acoustic" bridge. My son didn't want to have several guitars on stage. As it turns out the "acoustic" bridge was a very poor version of an acoustic guitar and he ended up with several guitars on stage.

Look at all the electronics and modeling that Fender is doing on the acousticsonic.

 

[schmee]

I have wondered about using a piezo preamp for a normal pickup. Tried it once with a mini switch for piezo/magnetic soundhole pickup. Didnt work really. It was a half hearted attempt though. I just ended up using two output jacks.
Often wondered if you could combine outputs....

 

[Freeman Keller]

I have wondered about using a piezo preamp for a normal pickup. Tried it once with a mini switch for piezo/magnetic soundhole pickup. Didnt work really. It was a half hearted attempt though. I just ended up using two output jacks.
Often wondered if you could combine outputs....

There may even be some issues mixing brands of piezos. I had a case to install a K&K in a guitar that already had a Fishman UST and I asked K&K about using the preamp with their pickup. They said they didn't recommend it but didn't say why.

I do know that most piezo's are very high impedance - in the order of a Megohm or so. Most guitar amps more like 5 or 10 K so you can't just blend them like you do two mag pickups.

 

[Freeman Keller]

Tomasz, I'll offer one more suggestion. I built an odd ball guitar for a guy who wanted "an acoustic that looks like an ES175". He swore he would never plug it in but frankly we were unsure what it was going to sound like. While the back was off I glued a set of K&K dots on the underside of the bridge plate and brought the output to a jack - no electronics. Since it was an f-hole guitar I only had one chance to do anything inside and I figured that if he never used the pickups we were only out a hundred bucks or so.

As far as I know he has never plugged it in.

 

[tomasz]

Thank you Freeman and schmee, that is a lot of good thoughts and inputs to think about.

I'm eager to experiment with this project and share back what I have learned on the way. My knowledge of piezo specifics is still to small to be able to judge clearly right now, but I'm leaning towards trying to solve the impedance equation and see if I can get the signals to blend.

I'll build a couple of different preamps and do some breadboard experiments in the next week or two, before attempting to installing anything on the prototype. I'll report back with progress or failure.

Thanks everyone

 

[crazydave911]

I install various piezo transducers in acoustic - K&K, Fishman, Braggs... - and if the manufacturer offers a preamp matched to their pickup I use it. The K&K are sound board transducers and they usually have an external preamp or DI to match impedance to the input of the amp and to offer some signal conditioning. I leave the choice to the owner - I don't have a need to plug in my acoustics.

Several years ago I helped my son with a solid body guitar with two magnetic pickups and a six crystal piezo bridge. The mag pickups got normal 2V2T controls, the piezo got its own volume control. There were no active elements on board the guitar. The piezo was brought out as a separate output on a stereo jack, that way it could be run thru its own signal chain. We did not try mixing the signals - the impedances would have been seriously mismatched.

View attachment 922449

The little PCB gathers the six signals from the piezo crystals, the pot on the far right is the volume for the piezo.

I'll add one more comment about this guitar. It was supposed to be the "every sound" guitar - two humbuckers with coil split and series/parallel connection plus the "acoustic" bridge. My son didn't want to have several guitars on stage. As it turns out the "acoustic" bridge was a very poor version of an acoustic guitar and he ended up with several guitars on stage.

Look at all the electronics and modeling that Fender is doing on the acousticsonic.

And Fender finally got it right. Just pickup an old Telecoustic and see what I mean. I had one, hated it but my foster son loved it. I made sure it went to the Navy with him. I figured Japan (where he's stationed) was far away enough

 

[tomasz]

To share some progress from the last days, I had some time to experiment with piezo discs and put together a quick JFET preamp, based on the schematics here:
http://hackaweek.com/hacks/jfet-audio-preamp-with-piezo-guitar-pickup/

It seems to do quite a good job, even without the optional 4.7 uF cap for higher output. I pluged it via the Presonus AudioBox in the DAW in parallel to the magnetic output. There was a slight difference in level and I think those few extra dB from the 4.7 uF, that I've ommited, would not be a bad thing. Here is the breadboarded amp, which is based on a surface mount JFET MPF102 for all you nerds out there :

I spent some time looking for the potential best spots to install the piezo discs, moving it around the guitar. They are are 27mm discs (1 1/16"), which is some amount of real estate. The headstock seems to be an interesting point of resonance, but cramping a disc there will be a challenge. The placement on the front works better than the rear of the headstock, where the sound gets muddy, probably due to the amount of wood on the way. That may be similar to placing a piezo in the neck pocket - too much wood in the way and vibrations probably get dampened.

With the front mount on the headstock the sound was interesting, a tad bassy and not high frequency heavy at all, and even playing further down the neck it delivered some interesting sound, which could compliment the magnetic output. Probably it wont do much of a standalone sound though. Listening back and forth to it, a blended signal might be very interesting, when treated further. Here is a sound example, it may not interest everybody, but there you go:



On each run you get the magnetic pickup, piezo pickup, both blended with roughly equal volumes. I used a partscaster nashville tele for the job. Positions are:
- neck
- middle
- bridge
- bridge & middle
- middle & neck

The differences may not be large in those examples, but probably amplified properly, more flavour could be expected. I find the in between positions to be very interesting, but for that I need to expand my knowledge on measuring resonant peaks and how to analyse the audio spectrum properly. Can anyone point me to solutions you use?

Taking into account, that the experiment was not ideal, but yielded some interesting results, I decided to proceed and build a prototype, where I can permanently place the discs on 2 or 3 spots:
- the headstock front
- route under the end of the fretboard
- The tremolo block - just for fun really

Here are some pics of the prototype being assembled. It's really a simple pine construction at this time with a maple fretboard and an ash top, for testing out some aesthetics.

Here is the piezo cavity under the fretboard:

Here is the pickup glued onto the fretboard:

Here is a test on the fit and depth before further cleanup and glue up:

 

[tomasz]

Moving on, I glued the pieces together and did some simple routings for the two single coils I plan and a Gotoh 510, tested for string alignment. It should be good enough for a prototype to move on:

On the headstock, I'm planing for using the Steingerber gearless tuners, because of their small footprint. That would allow the instrument to be shorter and more transportable. I really like how they mount and function: