anybody test it's item for power tube automatic bias regulation ?

milma · 18th June 2011, 08:22 AM

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)

dcgillespie · 01:49 PM

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

DF96 · 18th June 2011, 01:54 PM

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.

Cal Weldon · 18th June 2011, 05:25 PM

Moved to Vendors area. Please excuse the collateral damage.

18th June 2011, 08:22 AM	#1
milma diyAudio Member Join Date: Jun 2011 Location: Kassel Germany	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)

18th June 2011, 01:47 PM	#2
dcgillespie diyAudio Member Join Date: May 2010 Location: Ball Ground, GA	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

18th June 2011, 05:25 PM	#4
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Moved to Vendors area. Please excuse the collateral damage. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

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18th June 2011, 01:54 PM	#3
DF96 diyAudio Member Join Date: May 2007	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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