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Old 23rd September 2005, 11:17 AM   #1
DirkD is offline DirkD  South Africa
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Default Can I mod this circuit to use 6922 tubes?

Hi there

I built a clone of the Conrad Johnson PV10A, and was wondering if it would be possible to mod it for use with 6922 tubes.


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Old 23rd September 2005, 11:34 AM   #2
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Default 6922 mod

Yes you can, but that is like a new preamp. you have to change the cathode resistors for proper working, the RIAA must change and so on. The B+ supply is a little bit high for 6922.

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Old 23rd September 2005, 11:34 AM   #3
DirkD is offline DirkD  South Africa
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B.T.W. plaese ignore the phono stage. I am only interested in the line stage. Here is the component list.
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Old 23rd September 2005, 11:40 AM   #4
SY is offline SY  United States
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You can use the same topology, but going from a 12A*7 type to 6922 will involve a complete redesign. All operating points will be different, gain structure will be different, power supply requirements will be different, biasing will be different. Other than that...
"The way to deal with superstition is not to be polite to it, but to tackle it with all arms, and so rout it, cripple it, and make it forever infamous and ridiculous."- H. L. Mencken
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Old 23rd September 2005, 07:00 PM   #5
amperex is offline amperex  United States
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Default Fuzzy schematic

If I see the tubes right, they are 12AU7 to be replaced with 6922. Have you tried Brimar 12AU7 or Amperex 6085? They may outperform the 6922.

Note: 600 ma on the 6085 filaments, should not be a problem with the transformer operating too hot.
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