hooglebug Posted February 28, 2006 Report Share Posted February 28, 2006 when i bought a tunamatic bridge for a guitar i was building, i was mistakenly sold a piezo bridge (schaller gtm-p) rather than a normal one (which is a bonus and saved me a lot of money) but the trouble was i didnt know what to do with it. so i just took the small jack socket off and wired it to an on/off switch, volume pot and the master tone. it works fine as a third pickup and gives a kind of thin tele sound. but now i want the acoustic emulation. what i was wondering was is there any way to get this without a preamp? or am i just being stupid? the only thing is, if i was to have a preamp i would prefer it to be internal, but theres not much room left in the guitar for this unless i go over to the bass side (which is not very practical as its a flying v). theres just about enough room for a battery, but thats about it. which is why i was wondering if i could do without a preamp and just add a battery somewhere in the circuit. any help will be gratefully appreciated Quote Link to comment Share on other sites More sharing options...
JoeAArthur Posted February 28, 2006 Report Share Posted February 28, 2006 Most piezo transducers like to see a ultra-high input impedance of at least several megohms to provide good bass response - and good bass response is essential for that good acoustic sound. A simple jfet preamp can provide this... but you do need room to mount it... and a battery. It might be easier to just wire up the jack and use a strap mounted preamp. A little clumbsy perhap but it will give you the best sound. Another alternative is to use a stereo output jack, with one side for the piezo only and output that signal into a remote preamp. You'll want to keep that stereo cord length as short as possible. Quote Link to comment Share on other sites More sharing options...
fookgub Posted February 28, 2006 Report Share Posted February 28, 2006 (edited) Joe is correct... you need a preamp, and it should be as close to the guitar as possible. If you don't want to install anything in your guitar, have a look at this: FET Preamp Cable. I don't think any companies are making these, so you would have to make your own. It's a tricky bit of soldering, but maybe worth a look. Keep in mind that the preamp circuitry doesn't *have* to go in the jack housing. You could put it in your guitar, too. In a setup like this, you would probably want to run in stereo with your magnetic out on the tip and the piezos + preamp stuff on the ring. You could then bring this to an A/B box, mixer, or whatever you want to use to switch or mix the magnetic and piezo pickups. Anyway, I'm probably getting pretty far ahead of myself, but you could incorporate any switching/mixing circuitry you wanted into the floor box, and you'd be pretty well set. I have piezos on my guitar with the option of running mag/both/piezo in mono, but I still run it in stereo to an A/B/Y box. It's just easier to switch that stuff with your feet. Edited February 28, 2006 by fookgub Quote Link to comment Share on other sites More sharing options...
hooglebug Posted February 28, 2006 Author Report Share Posted February 28, 2006 (edited) hmmm, i'll have to ponder. if i got hold of a preamp circuit board (which i very well may be able to), how would i wire that into my existing circuit? it's probably going to be a circuit board from a preamp pedal. i'll explain whats in the guitar in case its relevant. aside from the piezo - on/off - volume - master tone, there are 2 humbuckers, each with their own on/off switch, phase reverse, series/parallel, hb/single coil, coil selection. each has an individual volume and they go to the master tone. now you see why theres not so much room. i may simplify it one day but its not as complicated to use as it sounds. Edited February 28, 2006 by hooglebug Quote Link to comment Share on other sites More sharing options...
fookgub Posted February 28, 2006 Report Share Posted February 28, 2006 hmmm, i'll have to ponder. if i got hold of a preamp circuit board (which i very well may be able to), how would i wire that into my existing circuit? it's probably going to be a circuit board from a preamp pedal. i'll explain whats in the guitar in case its relevant. aside from the piezo - on/off - volume - master tone, there are 2 humbuckers, each with their own on/off switch, phase reverse, series/parallel, hb/single coil, coil selection. each has an individual volume and they go to the master tone. now you see why theres not so much room. i may simplify it one day but its not as complicated to use as it sounds. I wouldn't trust a booster/preamp pedal to have the kind of input impedance you're going to want unless it's specifically designed for piezos. Honestly, the Tillman preamp I referred to before is a very clean solution, and it's one of the easiest circuits around to build. If you don't want to have a preamp in the guitar, then you'll want to hook it up as follows. If your guitar has a mono jack, you'll need to switch it out for a stereo jack. Leave the stuff for the magnetic pickups intact. Everything having to do with the magnetic pickups should come out on the tip terminal of the output jack. Bring the piezo output directly to the ring terminal of the output jack. You can keep the on/off switch if you want, but you'll need to remove any volume/tone pots on the piezo side. These controls need to come *after* a preamp. Now you'll need to connect your guitar with a stereo cable whenever you want to use the piezos. The piezo side of the output needs to go directly to a preamp, then to an A/B box, mixer, or whatever else you plan to use to switch between magnetic and piezo output. The magnetic pickups can go directly to your mixer, A/B box, pan pedal, or whatever. This is only one of many ways to get set up, but it's probably the simplest. You could also use a dedicated acoustic amp. After the piezo preamp, you can put a volume control, effects, or whatever else you want. The key here is that a preamp must be the FIRST thing the piezo pickups see, and the piezo and magnetic signal paths need to stay completely separate until after that. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted March 1, 2006 Report Share Posted March 1, 2006 Paul (Marossy) recently posted a buffer circuit designed for this exact application - a search for mintbox should hook you up. He's done a really nice writeup on his site, linking to the schematic and showing some good pictures of his build. This is small enough to easily use on board, if you want. Quote Link to comment Share on other sites More sharing options...
hooglebug Posted March 1, 2006 Author Report Share Posted March 1, 2006 thanks a lot guys. i'll have a go and see what happens Quote Link to comment Share on other sites More sharing options...
hooglebug Posted March 4, 2006 Author Report Share Posted March 4, 2006 just one question - on a stereo jack which is the tip and which is the ring? i know im a bit thinck with this stuff but i just dont know Quote Link to comment Share on other sites More sharing options...
fookgub Posted March 4, 2006 Report Share Posted March 4, 2006 just one question - on a stereo jack which is the tip and which is the ring? i know im a bit thinck with this stuff but i just dont know Quote Link to comment Share on other sites More sharing options...
hooglebug Posted March 4, 2006 Author Report Share Posted March 4, 2006 ah. thanks for that Quote Link to comment Share on other sites More sharing options...
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