Vacuum State FVP5A voltages

rhone · 29th July 2011, 02:34 AM

I have just finished a build of the line stage part of Allen Wright's FVP5A circuit and would appreciate some opinion as to the voltages I have measured.
Schematic is below. My PS is CLCRCRC with tweaked resistor values to get the desired 250V B+.
I am getting 160-170V on the anodes of the lower tube. Now this may be OK but my feeling is it's a bit high. What do you reckon?
Measured currents are about 3mA through the gain tube and 10 mA down the cathode follower bit.

SY · 29th July 2011, 02:41 AM

Yes, too high. It should be about 102-105V. Disconnect the CF and see what plate voltage you get on the voltage amp. Adjust the cathode resistor to get 100V on the plate (like it says on the schematic), then hook the CF back up.

Alternatively, if you have a pile of ECC88-oids around, you can change the input tube until you find one that gives you the right plate voltage for that design.

rhone · 29th July 2011, 04:07 AM

Thanks for that SY.
I have been using my "least desirable" 6922s to test the circuit. I'll put in the good ones and then adjust that resistor as necessary.

29th July 2011, 02:34 AM	#1
rhone diyAudio Member Join Date: Dec 2005 Location: Melbourne	Vacuum State FVP5A voltages I have just finished a build of the line stage part of Allen Wright's FVP5A circuit and would appreciate some opinion as to the voltages I have measured. Schematic is below. My PS is CLCRCRC with tweaked resistor values to get the desired 250V B+. I am getting 160-170V on the anodes of the lower tube. Now this may be OK but my feeling is it's a bit high. What do you reckon? Measured currents are about 3mA through the gain tube and 10 mA down the cathode follower bit.

29th July 2011, 02:41 AM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Yes, too high. It should be about 102-105V. Disconnect the CF and see what plate voltage you get on the voltage amp. Adjust the cathode resistor to get 100V on the plate (like it says on the schematic), then hook the CF back up. Alternatively, if you have a pile of ECC88-oids around, you can change the input tube until you find one that gives you the right plate voltage for that design. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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29th July 2011, 04:07 AM	#3
rhone diyAudio Member Join Date: Dec 2005 Location: Melbourne	Thanks for that SY. I have been using my "least desirable" 6922s to test the circuit. I'll put in the good ones and then adjust that resistor as necessary.

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