#1
Ok, to begin, I use a 1970s model Yamaha Fifty 112 amplifier when I practice with my band. However, the last couple of practices, I've been having some strange problems.

The amp doesn't have enough of its own distortion, so I use a distortion pedal to get some dirt. I have used both a Danelectro Cool Cat Distortion, and a Danelectro Cool Cat Metal Distortion pedal. The last 2 or 3 practices have been hell for me. Whenever I engage the distortion pedal, the amp begins to have this loud, squalling, absolutely ear-raping feedback. I'd used the distortion pedal with it before, without any trouble.

Other than the other gear, I use a Peavey Generation EXP. Could anyone explain why I'm getting this unbearable feedback? I'm at a loss...
If it's illegal to rock and roll, then throw my @$$ in jail!!!
#2
Feedback or oscillation caused by something else? Try one pedal at a time by physically removing all the others. Could simply be one pedal oscillating and have nothing at all to do with the amp. That would be the most likely problem imo.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#3
Not really oscillation...More like....the sound you get when you stand with your guitar's pups facing the amp. And it happens as soon as I turn on the pedal. Even with everything flat on the pedal, it still does it. My only choice is to crank down the gain to a level where it sounds absolutely atrocious. Also, its not the pedals. I've used them with different amps without any trouble.
If it's illegal to rock and roll, then throw my @$$ in jail!!!
#4
You've tested the pedals on other amps since this problem started? If so it's probably a faulty opamp or a resistor in the opamp's NFB cct gone faulty. Yamaha use a lot of 4558 chips in the preamp as a rule. Has the amp changed in other ways since the problem started? I don't suppose you have the schematic for it do you?
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#5
I don't currently have a schematic for the amp. I used the first distortion one week, and everything was fine. The next week when we practiced, it went **** all on me.
If it's illegal to rock and roll, then throw my @$$ in jail!!!
#6
Is it two channel? On the G50 and G100 Yamahas the two channels are separate circuits, ie, truly two channels. Is it happening on both channels? Try each pedal with nothing but it connected. You need to isolate what combination of things does it. Until you do that it's all just pissing in the wind.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#7
It's a single channel amplifier. No pedal engaged, its fine. Nice clean sound. As soon as I engage, feedback city.
If it's illegal to rock and roll, then throw my @$$ in jail!!!