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previous: Shea I wanted to bring up this topic thi... -- 12/12/2000 5:11 PM View Thread

Re: forget about matched pairs.

12/12/2000 7:22 PM
Rick Erickson
Re: forget about matched pairs.
Most interesting topic. I recently did a one-on-one  
tone tweaking session with a guitarist from a well known original ('60's) NW rock group. It was the classic - my Super Reverb sounds different after you fixed it. I ended up putting the original p/i plate resistors back in and he said "yeh, thats better"! I measured the resistors and ended up with 82K & 150K for the plate resistors. I installed some new cf resistors so as to minimize further drift.  
The rest of the mod involved putting some 220K anti-blocking resistors on the grids of stages 2 & 3 of a modified preamp and reducing the drive a bit to the 4th stage. It wasn't my mod job that I was tweaking, and it was based on a "Boogie" type circuit, so I was a bit skeptical that it would ever sound good to me, but in the end we both ended up with smiles on our faces. :)  
The Bedrock amps I've seen use 100K & 200K plate resistors in the p/i.  
There does seem to be some merit in unballancing the drive to the power tubes. Unmatched power tubes will do pretty much the same thing I would think but duplicating a good sounding set would be be more difficult than tweaking the amp to sound good with a matched set.  

Shea Thanks Rick. The pi mod sounds lik... -- 12/13/2000 1:16 AM
SpeedRacer There does seem to be some merit... -- 12/13/2000 3:37 AM