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Old 28th July 2009, 01:33 AM   #41
Brit01 is offline Brit01  United Kingdom
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Join Date: Jul 2008
Was doing some further reading.

This resistor after the output cap keeps the cap charged. It creates a small voltage to maintain the charge of the cap. hence it was bass shy as it was charging.

Is this correct?

I currently have a 500K to ground. If I reduce this it will charge up the cap a little faster?

I see on some headphone designs (Bruce Bender on Headwise eg) with big output caps there is a low 22K resistor to ground. This makes sense.
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Old 28th July 2009, 01:50 AM   #42
fredex is online now fredex  New Zealand
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Join Date: Jul 2005
Location: New Zealand
Without a res to ground the output voltage will rise towards the 170v you have on the cathode. Big Bang if you connect that to an amp input. The res is there just to keep the output at 0v, value is not critical but with a 1uF cap you could go a lot lower 100k. Too low and the stage will roll off the bass, too high and it will take longer for the output voltage to fall to 0v. cheers
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Old 28th July 2009, 02:17 PM   #43
Brit01 is offline Brit01  United Kingdom
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Join Date: Jul 2008
thks Fredex.

I'll have a go at changing that resistor value tonight.

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Old 29th July 2009, 02:32 PM   #44
Brit01 is offline Brit01  United Kingdom
diyAudio Member
Join Date: Jul 2008
Default B+ and cathode current controls

Just a thought.

Now if I want to use different 9 pin tubes, 6N1P, 6N6P, 6N2P etc... I could incoporate a variable resistor on the first RC junction (to adjust the B+) of my psu and another for the cathode resistor.

Also to add small meters to measure the B+ and Cathode current so I can fine tune and adjust for different tubes with ease.

I'd have a controlled range for the psu resistor so I don't exceed the limits of the 6X5GT recitifier in this case.

Sounds like a good idea?
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