Biasing for harmonic distortion with inverting stages...

[Amp Kat]

I thought the dual diode coring circuit in the PV Bravo->JSX was accepted as a variable (in the JSX) poor mans noise gate NOT a compressor? Some swear by jumpering it but others say it adds very little to the sound.

Yeah I think you're right that's what they refer to it as but it's really a compressor or bounding circuit which means compression. One thing we know is that it really is a poor mans design of a noise gate that cost under $1.

I can see where it wouldn't add much to the sound and as far as tone it's not supposed to as it only clips the signal or squares the ends and has no frequency qualities whatsoever. The pot just sets the amplitude and how much clipping takes place.

[Gtr_tech]

Cold stages to me insert a kind of "sticky" sound quality that I don't care for. Characteristic of a stock JCM800. It does sound a bit throaty, but theres this kind of "uneven" thing going on......a bit sputtery. Hotter biasing tends to make things too uncontrollable....a'la Messy Booger. I tend to shoot for the middle but toward the warm side....seems to be a good way to achieve a nice transition from clean to clipping. More natural....

[Gtr_tech]

I thought the dual diode coring circuit in the PV Bravo->JSX was accepted as a variable (in the JSX) poor mans noise gate NOT a compressor? Some swear by jumpering it but others say it adds very little to the sound.

I'm in the camp that jumpers it out. It *is* doing things to the signal....especially when you try to clean it up by lowering the input signal. The transition from full on dirty to clean gets real tough to make happen. You always have this weird upper freq clipping going on. It doesn't sound good.

I did the coring diode removal on a customer's Ultra Plus combo along with a tube swap (the bias circuit is kinda shitty on these and doesn't have enough available voltage to use certain tubes) to get a decent idle wattage of around 19w. The guy called me a few days later and said it was like a whole new amp. Well good then. Custy's happy....I'm happy....custy tells his buddies....I get more business. Good "press" is yer best friend in this racket.....