Bogen M120 bass guitar amp coversion

[Destructobot]

I'm brand new here, but I just picked up a couple amps for $100 on craigslist. The first is a Knight KN3050a. I've got some plans for that one, but should be fairly straightforward.

The other one is a Bogen M120. I read that this used 8417 output tubes - those are out of the question. I'm a musician and would really like to convert this into a bass amp. Could it be modded to used 6550's or KT88's? I read some old threads that seemed to suggest it can - but they weren't quite clear and were focused on hi-fi use I suspect. What are the pros and cons of the various tubes? What kind of power can I expect to get out of it? Any particular things I should do to make it sound good for bass guitar? I'd like it to have just a volume, treble, and bass knob. I don't need any other controls.

[whitelabrat]

You most certainly can convert the M120 to use 6550's. Look for a thread about the Bogen MX60a which should be similar. You'll probably want to find a schematic too.

I'd guess you can get about 120watt from that amp. It seems to me that a bass amp generally has a broader frequency capability than a guitar amp, so you could probably use it as-is without modifying very much and find the sound very satisfying.

[Tom Bavis]

Schematic will be here when Dave gets around to scanning it... http://www.schmarder.com/radios/schematics/index.htm

Give him an email.

[DigitalJunkie]

The other one is a Bogen M120

IIRC,the tube sockets are really close together.You won't be able to fit any "fat bottle" tubes in there. (well,ya might,but the envelopes might be touching.)

I think I have the schematic for the M120 around..
Schematic



Edit: Tom's link has a bigger cleaner scan!
Thanks Tom!

[Destructobot]

Digitial - are you the guy I bought the amp from down in Newberg? If so, ya straight up lied to me when you said it ran a pair of EL-34's and had been tested.