Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: billcreller on October 26, 2011, 12:42:26 pm
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A couple of years ago, I built a clone of a Valco/National, and inserted a Fender reverb circuit. The reverb worked fine, but the amp sounded "tinny" :w2: I figured it was the Fender infection from the reverb circuit, and just eliminated the reverb section. Well, it still sounded "tinny" ! :dontknow: So I tried another OT, which was a Hammond 1608. Big difference ! Couldn't believe it ! So I decided this week to do the reverb in it again. Anyway, I must have tossed the layout I made for the turret board, and had to start over, which I finished last evening. The layout came out different (?) than the first one :dontknow:
And it may even sound good this time.........
I had used all octal tubes, including the reverb section, with 6SL7s in place of the usual 12AT/AX7s........
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Bill, I've been scheming out a plan to use 6SL7's myself, with 6V6 for the power tubes. Was there anything in particular you had to do differently with the 6sl7s?
From what I've found, I should use an 82K plate resistor, and HBP mentioned I have to be more finicky with the heater wiring.
Thanks!
John
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John, I had hum problems with the heater wiring, until I replaced the pre-amp tube with a metal version. I figured it was just my layout, and rewired the heaters, but the hum persisted until I went with a metal version of the 6SJ7 pre-amp tube. Reverb used 1 1/2 6SL7s, with the same resistance and capacitance values as the 12AT7 and 12AX7 in the Fender circuit. Also used a 6SL7 for the PI, and it has 6V6 PP output.
Bill
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Got it. Thanks for the reply!
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I have it wired again, but it's not doing very good :BangHead: Went over the wiring vs the schematic, and made some changes in the layout, but it's still funky. Low volume, reverb wont work etc. More fun ahead..
Likely some dumb mistake that's obvious, except to me. :think1:
Twice in the past I used a 1K resistor in place of a 1M.......