Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bnwitt on July 18, 2010, 02:47:06 pm
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So I was googling bias vary tremolos and ran across this thread:
http://archive.ampage.org/threads/1/gadc/039997/Reduce_Beating_In_Modulating_Bias_Tremolo-1.html
Sounds very interesting. Has anyone implemented this?
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Whenever I have found beting to be a problem, it has been the oscillator, not so much the bias of the amp. I would rather not change the bias of the amp.
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I've built quite a few bias vary trem amps and none have the 'beating' you are describing.I assume you have one that does it?
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My understanding of bias vary trem is that the strength of the LF oscillation swing should be matched to the output tube bias voltage for optimum performance without any glitches. Colder biasing increases the range within which the oscillator output voltage can swing without clipping the grid(s) of the output tube(s). Alternatively the diode mod on stops the output tube grids from getting to 0V. At least I think that's how it works (for what that's worth). Another way of reducing/eliminating the tendency to beat is to increase the size of the build out/slope resistor in series with the output of the LFO stage and the output tube grid bias. Interested to hear other views on this
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I've built quite a few bias vary trem amps and none have the 'beating' you are describing.I assume you have one that does it?
Not when biased cold but I have experienced it when biasing hot. I thought this would be a cure for those players that like their amps biased hot. Just doing a little research.