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previous: Michael Polutta Earlier in this forum Ben looked at... -- 1115817004 View Thread

Re: "Dumbleized" Fender Concert (80's)

5/11/2005 8:06 AM
Re: "Dumbleized" Fender Concert (80's)
Thanks Michael!  
Some years ago I've buildt some 2-channel-amps based on Fender Dual Showman and Twin Reverb. I've used the chassis and transformers, but buildt the circuitry complete new on an eyelet board, I've designed for it.  
The left channel was "Blackface Clean", the right channel was "DOS", both channels with effects loop and reverb. The reverb's transformer I've putted onto the cap's dog house, so that I've got "the right place" for the 7-th preamp tube.  
Although I'd changed something in the ODS circuitry: From the 2-nd gain stage I (de)coupled with a .0047 cap, then with a 470K res. and a 470p cap in parallel to ground. But from the same point after the .0047 I went into a 3.3 RevAud pot in the function as a variable resistor (not as a voltage divider). After the pot with a 100K to ground and with a 56K grid stopper to the grid of the 3-th gain stage.  
The regular control between the 3-th and the 4-th gain stages I've fixed with a voltage divider 150K on top and 68K to ground. But again with a 56K grid stopper to the grid of the 4-th gain stage.  
This really worked fine and musicians said, that the amount of the overdrive is much better controllable than with the orig. ODS configuration.  
Another effect was, that at low gain settings the .0047 cap "saw" a relative high resistance to ground, to obtain more bass and warmth.  
At full gain the pot was shunted, so the cap "saw" only the 470K in parallel with the 100K, what cutted off the bass in a desired amount.