Rivera Amps and Feedback

Hi Everyone,

I just bought a used Chubster 40 off of ebay. I bought it mainly for bedroom playing. The wife was gone this weekend so I cranked it up a little higher than normal. The clean channel seemed to be ok, but the dirty channel had lots of feedback. I tried it with my les paul std and my lonestar strat. Both exhibit the same behavior. This feedback happens mostly on high volume (vol at 10, master at 4 or 5 with the master pot "pulled"), but it takes a higher master volume setting for the neck pup to feedback. When i turn the volume down on my guitar, the feedback stops. Muting the strings with my hand doesn't have an effect. It's pretty much uncontrollable.

I've never owned an amp with a master and a regular volume. So I'm not sure if this is normal. I'm assuming that the regular volume is used to saturate the power tubes, where as the master is used to simply control the volume out of the speakers.

Is this normal? Maybe bad power tubes?

Thanks,
Mark

Ok,

If I turn the master volume down (say at 7) and the regular volume up (at 6), there is a point where it feeds back. I also tested the clean channel. When both volumes are at 10, there is feedback.

I've swapped preamp tubes and I still have the same problem!! ARG! After I swapped preamp tubes the clean channel seems to be ok. The dirty channel on the other hand still has this problem, but seems to be at a higher volume.

Any ideas? A blown speaker? Need new power tubes?

Thanks,
Mark

How close are you standing to the sucker?
If you want to control your distortion, crank your pre amp and use your master vol to get the level you want. Adjust your pre amp to get the level of distortion you want. Small amps feed back a lot easier. Keep a good distance away from it when you crank it!

Just got an email from Paul Rivera.. Damn! Never thought I'd hear directly from "The Man"!! Anyway, he confirmed that it is in fact a pickup squeal. Beings I've never encountered this before, how can I fix this? Do I need to sheild my pickups more (I have a LP Standard and a Strat w/ Bill Lawrence pups)? Is this something that I have to just live with? How do you guys deal with this during gigs?

Don't let the power ratings fool you, these suckers are loud. If you crank it up that high, and I assume you're sitting fairly close to the amp, feedback's gonna happen.

Yea Phil, I am sitting close to the amp when its turned up that loud. I've just never experienced this before. My 60w Fender Prosonic seems fine - even at louder than normal bedroom volumes. I'll keep experimenting though. Some people have suggested that I get my pups repotted to help with the feedback. Thing is, I just dropped some Bill Lawrence's in my strat and *they even* feedback (I assume they are potted correctly). Maybe I sould back up from the amp a little too

Martin, I had my Jake combo turned up to about 6 or 7 yesterday with the gain set relatively high. I turned up the reverb a little and put a Voodoo Lab Microvibe in front and just started sustaining and bending notes and getting all kinds of crazy feedback like on Machine Gun. I felt like Hendrix with a good guitar! (Just kidding, I like strats too) spin

The Microvibe has been sitting in a box the last year or so, but I had so much fun with it that I might bring it to practice this week...

Riveras rule, I hope yours works out for you. (but the names are ridiculous...Knucklehead? Ninja Boost? CHUBSTER?! Now that's just sick! Great sounds though).

Oh say can you hear by the dawns early light..feedback...

I stand pretty far back from my Chubster...(which in my case is an appropriate name for my amp...unfortunately)...but for feedback with amazing distortion like in James Marshall Hendrik's Star Spangled Banner, I like the signal chain of a good humbucker or two into a BD-2 Blues Driver daisychained to a Mesa Boogie V-twin tube pre-amp into a 65 twin reissue. Since then though I think I blew a fuse in the V-twin..but don't think I was overdriving it with the BD-2 at the time, and so didn't get a chance to try this with the Chubster.

:wail: :dude