A single input jack connects to a normal and bright channel that can be mixed in any proportion. A switch is being installed to allow the normal channel to be cascaded into the bright channel for additional gain. This feeds an additional gain stage with a cathode follower driving a Marshal style TMB stack.
This is as close as I have to a current schematic.
i have at home 6922, only
1) The 6922 is a great tube for hifi but it is not really suitable for this application because of the same things that make it a great hifi tube. In a guitar amp you need a high mu triode or possibly a pentode. There are other high mu (70+) triodes out there but I don't have a list. Some have used 6SL7 (octal base) and 12AT7 (9 pin like the AX7). There are also probably suitable choices in the NOS 7 pin tubes out there.
6922 works great at the input of a guitar amp if you use it as a cascode.
Reviving a 4 year old thread.
Mike did you ever get this amp debugged and built?
Like electrofan I too am considering an amp with a 6922 in the input stage. The reason being is that I want a single amp to be able to work with an Electro-Acoustic guitar (like the Yamaha CPX/APX series) or a electric guitar (like a Fender Strat or Gibson Les Paul).
The idea I have is that the cleaner, low gain 6922 will offer a low gain input while a 12AX7 can offer a high gain input so the input (and gain/OD control) can be switched between the 12AX7 or 6922 each of which is configured for a particular design (electric for 12AX7 and 6922 for Electro-Acoustic) of guitar.
The TMB tone stack, PI and output stage can be common for both inputs and I like the 6V6 as it make most sense for a relatively light and portable tube amp using say a Celestion 10" (Gold) speaker.
