Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kenny1547 on May 27, 2019, 10:52:58 pm

Title: Bias measurement with bypass caps
Post by: kenny1547 on May 27, 2019, 10:52:58 pm

Hey guys!

I googled for days and just cant really find anything, so i thought i might ask here...

Is there a difference in how i would go about measuring bias with a cathode bypass cap on the power tube(s) if an amp is cathode biased? Since it can have more gain that way or rather changes how the tube operates, shouldnt it affect the power tube bias?

Until now i just measured bias with the voltage drop across the cathode resistor, but was never really sure about if the cathode bypass cap changes anything and cant seem to find an answer anywhere

Title: Re: Bias measurement with bypass caps
Post by: 2deaf on May 27, 2019, 11:13:57 pm

The bypass cap doesn't pass DC, so the idle current is the same with or without that cap.  Don't believe me?  Take the cap off and see if anything changes.

Title: Re: Bias measurement with bypass caps
Post by: kenny1547 on May 28, 2019, 02:12:17 am

No id definitely believe you! I just wasnt sure, thought that it might be more stress for the tube since it operates in an altered way, thanks for clarifying!