Quote from: J M Fahey on October 28, 2015, 08:59:40 AM
That L R Baggs preamp is *very* good.
I just calculated the "mystery gyrator" frequency and it's surprising (or not? ) 95 Hz
Clearly it adds body to turn usually famigerated "Piezo shrillness" into nice warm fat sound, without losing top frequency transparency.
AFn excellent design ... although you'll have to design your own PCB .
This one is for dual mics, Piezo and Magnetic, if you use just the Piezo, you can simplify the design quite a bit, since you need neither the Magnetic preamp nor the mixer, in that case V1 volume pot can straight go to output jack.
That's very interesting JM. Can you explain how you calculated the frequency affected by the Gyrator, I'm geussing the Gyrator (i had to google gyrator to find out what it was ), acts as an Inductor, so is it some kind RLC filter..maybe a bandpass?? Am I completely on the wrong track?? I've been recently playing around with some homemade piezo disc pickup/contact mics. Still yet to get that magic sound. There sure are a lot of schematics on the web and ideas about how to tame these piezo devils.
Have tried Tl072 chargeamp based circuits, and various well known things like Tillman and offshoots. I got a some largeish discs, some salvaged from buzzer, and these really small ones that are very trebley/high end. Have tried mounting the bassy one and the treble disc feed into a 2 stage jfet preamp that I found on a ham radio site, I added 10m input resistor. I then added a passive mixer - just 2 - 10k pots - 10k resistors. It works but the larger disc really over powers the smaller. I only have 1k, 10k, 20k pots on hand. I tried a 20k pot on the smaller and got more signal in the mix. But it lacks a bit of sparkle, and its now lost a bit of volume.
keen to give this one try on the breadboad before I get out the soldering iron and commit to my lastest version. I have mpf102, and some BC 54x . Would they be ok this LR Baggs circuit?? If you have suggestions..I'm here to learn..cheers