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Author Topic: Need advice for "easy" preamp.  (Read 5138 times)

armstrom

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Need advice for "easy" preamp.
« on: March 15, 2008, 05:07:32 PM »
I am brand new to the forum and have been trying to soak up as much info here as I can but I'm still in need of a bit of "spoon feeding" :( . So, please forgive my obvious "noobness".

I have built and tested an "AMP6 Basic" kit from 41Hz.com ( http://www.41hz.com/main.aspx?pageID=118 ).

So you don't have to read the website, here are the vitals:
  • 25W x 2 output
  • based on Tripath TA2020 chip
  • powered by 12V DC "brick"

So, I want to turn this guy in to a little practice/small gig amp for a friend. I'm either going to have a single guitar input that just gets duplicated on both channels (one preamp) or a guitar preamp on one channel and a mic preamp on the other.

I am having serious problems deciding what to do about the preamp stage. Can I simply use one of the many pedals adapted from old tube amps? (like the kits found here: http://olcircuits.com/olckits.html).
Or, am I forced to build something custom? My goal is to cram the preamp and power amp into a smallish enclosure and run cables to satellite speakers.  My initial plan was to build a simple JFET preamp circuit found here: http://www.till.com/articles/GuitarPreamp/index.html but I'm not sure if that has sufficient gain, and it lacks a tone stack.

I would like something that can run off the same 12V power supply I already have for the power amp. 

Any suggestions? I can build a kit with the best of them, but get very frustrated with perfboard and trying to source obscure parts so I would be more than willing to pay a bit extra for a ready to assemble kit.

Thanks for your patience and any advice you can give.
-Matt Armstrong

darwindeathcat

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Re: Need advice for "easy" preamp.
« Reply #1 on: March 16, 2008, 09:30:51 PM »
I'm a relative noob myself, but we've had a great discussion about using those ROG pedal designs as preamps in the thread "Preamp for lm 3886" that here in this forum. Several of the ROG designs are available as kits from OLC. You can also get a kit from Tonepad.com for a similar JFET preamp to the one you referenced...
   The bottom line (as I have been able to figure it out) is that YES you can use those tube-emulating pedal designs as preamps. They should all run at 12v with out any design modifactions (since you use adjustible trimmer-resistors to set the bias for the transistors in all the ROG designs, and I believe that the bias voltages would be only thing you need to change to make them run on 12V instead of 9V)...
  I'll let the more experienced members here add to my comments if I have mispoke...
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armstrom

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Re: Need advice for "easy" preamp.
« Reply #2 on: March 17, 2008, 09:03:13 AM »
Thank you for the reply. I decided to buy a Behringer GDI21 to try. At $30 it's much cheaper than any of the complete pedal kits out there. I plan to disassemble the pedal and integrate the electronics into my enclosure. I'll post agian once I have everything done and tested.
-Matt