piezo preamp

[tmenss]

Keep it simple and build it

The worries about the residual impedance mismatches are neglible compared to NOT using a buffer preamp. Use the Tilman cicuit (j201 FET) or an MPF102 from Radio Shack. Its best to order a few dozen and swap them out on your first circuit. I had a bunch of reistors so I swapped out source reisstors till the drain voltage was within spec. Google "Hawes MPF102" there are pracitcal troubleshooting tips for working with fets in general.



http://music-electronics-forum.com/u...6-albums90-559
http://music-electronics-forum.com/u...6-albums90-558

cheers

[tmenss]

More gain

To increase the headroom of the circuit you may try using higher voltages

MPF102 FET Preamplifier FAQs

[artantaaa]

Thanks for the reply. I installed a pot to control the drain voltage and set it for 5.5V. This was the last thing I did to the preamp. Now that I've got a working solution and I can hear my bass over guitar and drums, I haven't been as focused on the electronics, but my setup still needs a lot of work. I still have to run the preamp output through my equalizer pedal and turn my amp up to 8 or 9 to get a decent volume, and the sound seems far from ideal. I'm thinking I need a lot more gain from the preamp, because if I plug my guitar directly in to the amp set at 8 or 9, it seems twice as loud as the bass through the preamp and eq pedal. The next thing I plan to try is to bypass the source resistor with a 100uf cap, as Fahey and Kreuzer suggested, but I'm not sure that it will give me enough gain to take the eq pedal out of the chain. How much gain would I get by adding a second 9V battery and readjusting the drain voltage? I plan to try this as well. If the capacitor and additional battery don't give me enough gain, the next step will be multiple J201 stages. I've been warned that it will cause clipping, but I figure I might as well see what it sounds like because I bought a whole bag of them. Would a regular, or non FET, transistor be a better choice for amplifying my signal?

I'd also like to thank everyone for all of the replies I have gotten so far. This forum has been a great help in this project. I have a little electronics experience from a job I had installing car stereos, and rewiring a few old cars I've owned, but this is the first time I've done anything with transistors. Even if you can't comment on the circuit I'm working with, I'd really appreciate it if you could direct me to some good resources on basic amplifier theory.

[tmenss]

gain

While I haven't experimented with bass pickups, I would think that increasing the headroom of with higher voltage designs and using the bypass capacitor would be an easy first step to try with the preamp. Personally on guitars the simple FET circuits at 9 volts rarely provide more than unity gain without running into some non linearity. Two stage designs are beyond my experience but the circuits are so easy to build why not try(if you have the time!). Try searching for the AMZ minibooster a two stager FET preamp. plus there's a whole subculture using this as a basis for pedals. How about different piezo materials? Here are some links that may be useful.

Piezo Materials
Piezo Materials
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[thehallofshields]

Anyone experimented with or have any ideas on modding an EQ pedal (I'm thinking a cheap Boss GE-7) for a higher input impedance and skipping the on-board preamp?

It also seems debated across forums whether cable length is as important with PZT (capacitor-like) as magnetic-coil (inductor-like) pickups. I also see conflicting information on whether standard impedance calculations work when PZT's are placed in parallel. Can an expert clarify?