Ampeg hack butchery project question

[Luthierwnc]

Hi again,

I'm putting the finishing touches on a couple amp projects that were derailed by employment opportunities. One of them is a Gemini II that was a ground-up restoration with a completely new board. For fun, I put in a 5F6-A circuit on the accordion side. It works but is too harsh running through the 7199 inverter. It is also quite a bit louder than the domestic James stack. I'm using a 12AY7 in the one hole and I've taken some hair off the front end with cathode cap and grid leak mods but it still has an unpleasant breakup past about 6. The Gemini side sounds just like it should.

Anyone know of an interesting non-Ampeg amp design that used a 7199 PI that I could scab onto the board? It can't use more than two preamp tubes. Something off the wall would be especially interesting.

Cheers, sh

[Phil_S]

Gibson used 7199 in quite a few amps. I'm not sure if it was used as a PI or not. You might want to search here to see which amps: http://www.superiormusic.com/page199.htm

[Luthierwnc]

Thanks Phil,

The schematics I've seen usually use them to drive the reverb pan. I might just throw something Blackface at it and see what happens.

On the topic of Gibsons, two very worthwhile homebrews are the 5879 GA-40 Les Paul amps and the late '40's BR-1. The latter is a beast. It was the Rock Around the Clock amp. sh

[Luthierwnc]

If anyone cares, I used a Blackface preamp in the second channel and it works a lot better. I may still replace the .1 and .047 tone caps with .033's or even .022's but for now it is useable and slightly louder than the stock James preamp. I did reduce the second stage coupler from .022 to 500 puffs since the bigger one was throwing too much at the inverter. There is also a little bleed from the tremolo bug if I leave that on. Just have to tolex the cab and air it out. Cheers, sh