Hey teleman, I actually invested in a Peterman Piezo transducer for one of my acoustics. It has great gain WITHOUT a preamp (plus no associated impedance matching/noise coupling/power supply/ad nauseum). It has to do with the type of transducer it is, that utilizes all three types of force to produce current- pressure, stress, and flexure. It sounds amazing. Look it up online. However, PLEASE DON'T give up on your circuit! I am prototyping a boundary mic built right in to the bridge of an acoustic I'm building. I started down the same road as you, and ruled out many things. First, microphones are better transducers of acoustic sound than piezo elements, second, balanced line level with phantom power is the ultimate way to go, in that the signal is twice the potential no matter what the gain, and phantom power eliminates onboard power needs. Thirdly, most modern consoles have better secondary preamp stages and better tone controls than anything you could build onboard.That just leaves creating the best high-impedance preamp to balanced output line driver to XLR out...which I am still working on...and might need your help myself.
Thanks Marvin....
As you may have noticed my post is now nearly 4 yrs old! Thanks just the same for your reply. I've come a long way since then...I've designed my very own Mic-Piezo blender pre with all the bells & whistles you can think of! I did struggle for a year or two,but asked a lot of silly questions here there & everywhere! Read & researched a lot. Built 5 proto-types before cracking it! It took me ahh, just over 3 yrs to complete it.
One question remains though! How can I modify this circuit to supply 12/15V DC from a 15V DC supply instead? I'm thinking in lines of "T" power circuits!
As you may have noticed my post is now nearly 4 yrs old! Thanks just the same for your reply. I've come a long way since then...I've designed my very own Mic-Piezo blender pre with all the bells & whistles you can think of! I did struggle for a year or two,but asked a lot of silly questions here there & everywhere! Read & researched a lot. Built 5 proto-types before cracking it! It took me ahh, just over 3 yrs to complete it.
One question remains though! How can I modify this circuit to supply 12/15V DC from a 15V DC supply instead? I'm thinking in lines of "T" power circuits!
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Oooops! Didn't even look at the date. I got a reply from DIY in my mailbox, so thought it was a current thread. Sorry. I'm glad you've made progress. To be honest, since they started coming out with high quality very low-noise op amps, I've steered away from discreets. I've been so busy trying to trim out my guitar prototype (I made my own purflings using laser etching) that I haven't got back to my preamp. I appreciate the feedback on the 'Linkwitz mod' however, needed to hear from someone that it really works. Thanks for the reply. BTW, my first name is John. Last name Marvinkite (Don't worry, I get that all the time. My nickname in H.S. was 'Marv'.
I have also been playing around with building onboard acoustic guitar preamp as well. This schematic seems to be designed using phantom power. If you google something like "diy phantom power", you will see quite a bit info about how to add phantom power to this kind of circuits (usually with two 6k8 resistors match to within 1% and non-polarized DC isolation caps).
I also hate Artec. Bad sound quality. Their piezo pickup has very low output and sound tinny even you feed it to a high impedance preamp (even their own matching preamp which use opamps !). I have since taken off all my artec installation.
I don't have US$160 for a Fishman matrix (which I like) so I install a Fishman sonicore (coax) under the saddle and feed it to my FET preamp. I don't like opamp since the signal has to go through a bunch of transistors inside the opamp before it gets out of the 1/4" jack (meaning more distortion). The simple FET preamp gives very pure sound. I'm working on a 2 stages FET preamp with simple passive tone control. I'm not using active tone control just to maintain the highest linerality I can get from semiconductors. I'm sort of treating my preamp like a HiFi preamp. Be sure to use audio grade capacitors along the signal path.
I have fixed a friend's Fishman blended preamp but although it sounds wonderful, it does have feedback problem during live playing when using too much mic. I'm sticking with my sonicore (coax type) under saddle after working on many piezo pickups with various problems. The sonicore gives the best strings balance and is more forgiving for uneven pressure between saddle and the bottom of the slot.
I know this is an old thread but just happen to stop by here today and trying to throw in my little experience.
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