Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bnwitt on December 05, 2015, 01:26:14 pm
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I am about to start my BFDR build and I've pretty much decided to go with the Hoffman 2 channel AB763 circuit again. I've got a question about the tremolo ticking of the original Fender BF amps which may push me over the line to Hoffman. This amp is going to be for my studio so I want the best possible tone and a great sounding tremolo for my recordings. I have built numerous Hoffman AB763 amps like the Cesar Diaz mod Vibroverbs I built several years back along with some Hoffman BFDR conversions in Fender reissue 65s and none of them ticked. It is my understanding from my research that the ticking in the original BF AB763 amps' roach type tremolo is due to a property of the Neon lamp in the roach. If this is true, then I assume it cannot happen with the brown era bias vary oscillator used in the Hoffman circuit and that would be the nail in the original BFDR circuit as far as my choice is concerned. Now I've also done repairs on quite a few BF AB763 amps over the years and only had ticking in a few of them which was fixed or minimized with some component additions. So what's the verdict. Is the ticking only a roach tremolo problem or are bias vary tremolo oscillators capable of the same fault?
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Bias vary trem has no ticks, fleas, or other bugs. It can sometimes be hard to get a strong trem with big tubes without fiddling the bias setting. I just built that circuit to wiggle a pair of 7591s and the trem is very strong and smooth.
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Steve,
Thanks for the reply. I remember the issue with 6L6s and weak tremolo on my Cesar Diaz Vibroverbs. I used the fix someone in here gave me which is attached. On to my Hoffman BFDR build. I'm excited to have some amp building time now. It's been a long dry spell. I hope you are doing well my friend.
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Barry, take a look at Doug's new layouts and schematics. He reworked all his stuff using Visio. Looks much better. May be some slight changes too.
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Will do Steve.