AMPEX 620 Mod?

[shiner555]

Hi Guys,

I recently picked up one of these amps from a family friend. It had the wrong tubes in the output section and had problems in the power supply. After a re-build and tube replacement, things are back up and running! However, the amp does not have much gain at all. From what I've read this amp was not designed for guitar but as an accompaniment speaker to an ampex 2-track tape deck.

http://recordist.com/ampex/schematics/620man/620-2.pdf

I'm thinking about making some changes to the front end 5879 tube to get a bit more gain out of the amp. Maybe make it more like the ampex 612.

http://recordist.com/ampex/schematic...n/ampex612.jpg

However, does anyone have any suggestions on some things to try out? Maybe move the vol pot to after the 5879, add grid stopper, etc.

Any suggestions would be great!

Thanks!

[olddawg]

Personally, I would gut it and start over using as a template the guitar amp of your choice that uses 6v6s, has the same ballpark B+ and you have enough heater current. Check out the Ceritone, etc site for schematics and layout diagrams. Or...you could try run a rack preamp/processor or even a boost pedal on the input.