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Old 17th July 2008, 03:12 PM   #1
BL21DE3 is offline BL21DE3  Scotland
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Question Using a Maida Regulator with a CCS

Hi Folks,

I'm thinking of implementing the Maida regulator as used in SY's Red Light District amp to regulate the screen voltages of the output EL84s in my amplifier. However I use a CCS to set the current on the cathodes of my EL84s. Having read SY's thread on his amplifier design and the additional details on his website I noted that the regulator is adjusted on test by to give the desired cathode current.

Therefore my question is if the cathode current is fixed by my CCS how would I adjust the voltage of the regulator? Or is it case that the regulator could be built to output a specific voltage because we know what the cathode current will be?

Any help would be appreciated.

Regards,
Ewan
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Old 17th July 2008, 03:34 PM   #2
SY is offline SY  United States
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Quote:
Or is it case that the regulator could be built to output a specific voltage because we know what the cathode current will be?
Bingo!
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Old 17th July 2008, 04:18 PM   #3
BL21DE3 is offline BL21DE3  Scotland
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Thanks for the reply SY.

So having now worked out that the regulator can be built to a specific voltage because I know the current that will be present at the cathode.

My next question is how do I determine this voltage? Apologies if this is blindingly obvious but I'm not quite up to speed on all my tube/electronics theory.

Regards,
Ewan
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Old 17th July 2008, 04:23 PM   #4
SY is offline SY  United States
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To a very close approximation at high voltage, the output is 1.25 times the ratio of the set resistor (the big one from ADJ to ground) to the return resistor (the little one from OUT to ADJ).
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Old 17th July 2008, 04:42 PM   #5
BL21DE3 is offline BL21DE3  Scotland
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Thanks for quick reply SY.

So I now know how to set the output voltage, which seems straightforward enough. My only remaining question is how would you determine the required output voltage for a given cathode current? i.e say the CCS sets the cathode current at 70mA for the tubes what voltage would the screens need to be run at?

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Ewan
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