6cg7 and an upgrade?

[pro_crip]

I'm just about to hit the wiring phase of my fpiii and I was wondering about said tube. I know of at least 1 crack that was modded to use a 6cg7 in place of the 12au7, can the 12au7's in the fp be replaced with them as well? Right now I'm building the stock fp and once I get it up and running, install the upgrade. Speaking of the upgrade can I install everything in the upgrade except leave the od3 in place. I just like the look of those od3's and I wanted to leave it in there with the upgrade. Thanks for listening.


Rich

[Paul Joppa]

The 6CG7 is close enough that the main circuit does not need tweaking. The heater power supply requires a change of resistor since the 6CG7 draws twice the current, and of course the tube sockets must be wired differently. The 6CG7 is the same as a 6SN7 except for the base (9-pin mini vs. octal) and you can find threads on 6SN7 conversions with a search.

Yes, you can install the C4S loads and leave out the dual-mono power supply and active shunt regulator circuits, keeping the 0D3 if you like.

[pro_crip]

Would this be the heater resistor change? (from grainger49's thread):
The only change to the schematic is the resistor in the heater DC power supply, from 0.62 ohms stock to 0.22 ohms for two tubes (stock configuration) or 0.10 ohms for three tubes (upgrade configuration) The heater connection would be to pins 4&5 (on the 6cg7) and leave 9 floating. Thanks for listening

Rich

[Paul Joppa]

That's it!