Simple Tube PA > guitar input?

[Arn C.]

Howdy All !

   I have an old bogen challenger 10 watt tube pa with 2 tubes- 12ax7 and 7868.  Model #CHB10A.  It has two inputs one is phono and the other mic.

The mic input goes directly to a .01 uf cap and then to the 12ax7 pin 2,
The volume pot for the mic  has center tap going through 470K resistor to a .01 cap to pin 1 of 12ax7,  one side to ground and the other side to pin 7 of 12ax7.

The phono input goes to one side of phono volume pot, the other side to tone pot, and the center lug through a 220k resistor to side of mic pot that goes to pin 7 of 12ax7.

Which input should I use for guitar and what modifications must I do to accomplish this?

Any responses would be appreciated.

Thanks!
Peace!
Arn C.

[al3151]

Go to- http://ax84.com/bbs/

They should be able to offer great info(input )on the subject.Me?,I would plug into the mic input replacing the input cap with a 68K resistor and a 1MEG resistor to ground.I would not want anything else in the signal path to the first stage.I AM NOT A TUBE TECH but have built a P1 amp from ax84( It was lots of fun)and trying to learn what I can.

[Clipped]

Arn -

Gotta get that first post in sometime, so here I go:

http://www.geofex.com/  Go to the section on Tube Amps and there is a good article on converting PA type heads to guitar use.

Hope that will help.

Good luck,
Ron

[GreenEye]

7868s sound so great clean!  My favorite tubes on planet earth.

[Aharon]

I modded a couple of CH10 amps.
You can make them into champ-like beasts or similar like the Premier 50.
Aharon

[Somicide]

Cool, now who knows anything about the MX30A PA by Bogen?  This is my current project...

PnL,

Jeff

[Dean Hazelwanter]

Arn, send me your email address to dean{dot}hazelwanter{at}sasktel{dot}net, and I'll send you a schematic. I grafted a champ-like (with modified tone stack) front end onto a CHB-10A. It sounds *real* nice!  

[Arn C.]

Thanks Gents for your help!

Peace!
Arn C.