Using this information is entirely at your own risk. I try to make the information as accurate and complete as possible (it sure isn't yet), but don't rely on it. If you "try this at home" and for some reasons get hurt and/or anyone else I can't be held liable for your actions. Nobody forces you to do anything, at least I don't. Some of the schematics use high voltage connections (power adaptors). Use the appropriate caution when dealing with such voltages. If you don't know how to handle this safely, don't handle it at all.
Gee, seems like one can't offer anything these days without some legal disclaimers...
This is a little collection of schematics I've created basically for a bass
player forum called http://www.bass.de/.
There is no particular order, system or theme, it's more like a brain dump. Hey, what do you expect for free? :P
Since the forum mentioned before is in German most schematics have remarks in German, however, they should be readable for non-Germans as well. :)
Most schematics here have been created by myself. There is no usage limitation, no secrets, no rocket science here.
This pre-amp is meant to be housed in an external case (e. g. 19") not to be built into a bass. I used this kind of setup for a while. I liked the sound, but the weight of this pre-amp, the Behringer EQ and Compressor along with the 3 rack units plus power amp simply was too heavy for me. Still, in a fixed setup it's a real great sounding alternative. The circuit below uses a +/- 15 V DC symmetrical power supply.
See also: Thoughts on Bass Sound Shaping
This one is suitable for active PUs.
This one is suitable for passive PUs. It also has an impedance matcher and booster with adjustable gain trimmer.
Basically the same as 2 but no adjustable gain.
Don't do this. It's not wise. It also drains your battery.
This is a bit better, doesn't drain the battery but one potentiometer is unused. So what? :)
This one is with 1 MOhm input impedance and adujstable gain.
Same as above but to be used with an external power adaptor. It was successfully tested at 12 V DC.
The result can look like this:
Helmuth Lemme, Elektro Gitarren-Elektronik Teil 1, Seite 161, ISBN 3-7724-0278-X.
This book is in German. There is an updated version (also in German) available from:
http://www.gitarrenelektronik.de/ (Helmuth Lemme's web site - from the man himself!)
Meyer, Operationsverstärker, 2. Auflage, Seite 45, ISBN 3-7905-0659-1 (this book is in German)
Fender/Sunn schematics coming with the unit. I wished other vendors did the same!
Here is what the serial version can look like:
Here is what the parallel version can look like (well, it's 4 times ¼" to 4 times Speakon):
I wonder why someone comes up with a 1200 W at 2 Ohms amp using ¼" connectors. Speakon is better, safer and the more appropriate choice.
It's basically the same as the above but the transformer is external and it's 12 V DC. I've built this for someone and I like to document things, otherwise I might not have bothered to draw this modified version. ;)
OK, this is *very* trivial.
Thanks for constructive feedback from: