Simple mod....probably

[TG]

So add the volume pot at the arrow here, one side gets the input and the 470k ohm resistor to ground and the other the 10k ohm grid stopper.

No. Just add the pot before the complete cirquit.
Input signal to the top, ground to the bottom, wiper to the junction point of 470k (probably worth increasing to 1M for 100k pot, but not really necessary) and 10k resistors.

 

[JoeAlders]

Why? At power up the tubes are not conducting until they warm up.

G²

There you have a good point!

 

[bubbazanetti]

No. Just add the pot before the complete cirquit.
Input signal to the top, ground to the bottom, wiper to the junction point of 470k (probably worth increasing to 1M for 100k pot, but not really necessary) and 10k resistors.

got it!


BTW, someone had asked earlier, this is on a Magnavox 175FF chassis, 6V6 amp.

 

[jhstewart9]

Fender AB763 Instrument Amplifier

For all those who have never bought a book on toobz electronics, here is an example of a circuit similar the the subject of this thread. There are many others like this in Aspen Pittman's book.

 

[FlaCharlie]

BTW, someone had asked earlier, this is on a Magnavox 175FF chassis, 6V6 amp.

That was me, thanks. I thought you were modding the PP 6BQ5 version since those are the output tubes in the schematic you posted.

I modded a 185 recently, which is essentially the same as the 175. I switched from 6V6s to 6N6Gs and used the 5751 input / phase inverter circuit from a Leben, which is a highly regarded Japanese PP EL84 amp that sells for $3500. The 5751 is a 9 pin that has the same gain as the 6SL7.

Here's a link to that build, if you're interested:

Magnavox 175/185 Build . . . With a Twist | Audiokarma Home Audio Stereo Discussion Forums

I never did draw up a schematic for it, probably because it was such a simple mod. I guess I need to sometime.

I assume you have a schematic for the Maggie 175. If not, here's the Sams. It's in pdf and can be enlarged to show detail.

I've got the Leben schematic somewhere too. I can post it if you're interested.

 

[jhstewart9]

One cathode resistor for all four of those 6V6GTs is not the best idea. But a way to save $$$ in a consumer product. The amplifier in the thread would be adequate but not really hifi. Lots of harmonics, the phase inverter is a problem. But the guitar pickers love that.
Still OK for a rebuild.

 

[bubbazanetti]

I assume you have a schematic for the Maggie 175. If not, here's the Sams. It's in pdf and can be enlarged to show detail.

Yep, thanks, appreciate the extra info!