anybody test it's item for power tube automatic bias regulation ? - diyAudio
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Old 18th June 2011, 08:22 AM   #1
milma is offline milma  Germany
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Default anybody test it's item for power tube automatic bias regulation ?

I found it by ebay, follow the link .....maybe its usefull for my 50 ma DYNACO EL34 tubes ??!!

thx, Mell

Automatic bias regulator for tube power amplifiers KT88 bei eBay.de: Amplifiers Tube Amps (endet 04.07.11 12:04:28 MESZ)
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Old 18th June 2011, 01:47 PM   #2
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With an internal resistance of 1000 ohms, at the very least, power output would be reduced over that of an otherwise fixed bias design. Overall, I'm not sure what this product is providing over that of a cathode bias resistor and large bypass cap.

Dave

Last edited by dcgillespie; 18th June 2011 at 01:49 PM. Reason: clarity
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Old 18th June 2011, 01:54 PM   #3
DF96 is offline DF96  England
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This appears to be a CCS, but an internal dynamic resistance of 1k sounds a bit low. A CCS is a good way of ensuring that the bias for the output valves is wrong, as it controls the wrong thing: average current instead of quiescent current. A cathode resistor is better. Better still is either fixed bias, or a zero crossing sampler which actually controls quiescent current.
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Old 18th June 2011, 05:25 PM   #4
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