I have an Ampeg B200R that started developing a few problems. First thing I noticed was when I would turn the amp off, it would make a fairly loud crackly noise. Then after a few days of that, it became very distorted even at low volumes. It sounds like I am playing through a fuzz box. I changed the tube, same thing. I plugged into another speaker, same thing. Any suggestions on what to look for next?
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Ampeg B200R - distortion issues??
- Thread starter gbrooding
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- ampeg distortion issues
These amps have had numerous problems. First off, we need to see that your speaker cab had the connective short on the jack board in the speaker cab. It will either have a correct replacement board, or a trace cut to stop the dead short on the "no tweeter" jack.
The chassis design and material is hokey... the bent tabs that hold the cage nuts, will break off.
The bias should not drift. Mosfet amps like these are a fine balancing act, and the bias circuit should not be messed with by anyone...except for an actual tech.
The preamp tube is used for the initial gain stage, and is not pushed very hard, voltage-wise. So as long as you don't drop the amp, will be reasonably durable. If you had a shorted tube, it can screw up the opamps (TL074) that drives the ultra switches, and tone stack. Chances are good, that is where the fuzziness is.
I have been in a couple of these amps, the boards are wave soldered, and done well.
Issue on one amp... was someone plugged a phantom powered cable into the DI, which took out the opamp that drives the DI and the phone jack.
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The amp in my B200R loudly and completely self-destructed as a result of a crack that developed in the unbelievably flimsy chassis. The crack resulted in an internal short that fried the electronics. Mine is a later Chinese version and chassis cracking on those seems to be a very common issue based on other B200R threads on TB.
My solution was to remove the chassis and replace it with a PF-350 micro head. The cabinet is now a lot lighter and the head and cables fit easily in a laptop bag. And the great sounding B200R cabinet is now powered by 350 watts instead of 220.
A definite win-win!
My solution was to remove the chassis and replace it with a PF-350 micro head. The cabinet is now a lot lighter and the head and cables fit easily in a laptop bag. And the great sounding B200R cabinet is now powered by 350 watts instead of 220.
A definite win-win!
Looking at the rear of the amp, all the way down the left side due to the heavy transformer. The amp was never dropped or handled roughly (it still looks brand new).
Regarding what blew, my amp tech told me but I don't recall exactly what shorted out. I do remember the ear--splitting buzz and the smoke. My tech told me it wasn't worth fixing and IMO it sounds better than before with the $299 PF-350. I don't miss not having a preamp tube. By the way, the fuse didn't blow during the implosion.
Here's the rear view without the original amp in place.
Regarding what blew, my amp tech told me but I don't recall exactly what shorted out. I do remember the ear--splitting buzz and the smoke. My tech told me it wasn't worth fixing and IMO it sounds better than before with the $299 PF-350. I don't miss not having a preamp tube. By the way, the fuse didn't blow during the implosion.
Here's the rear view without the original amp in place.
