valveking 112

[JC@]

I've read that this amp can be set to class A or AB
Is it true, really?
I don't have a schem for it which I may need If I decide to mod it.
Would it be possible to add an adjustable bias circuit for this amp?

I can't see how can they be class A and AB with the same B+ and bias circuit, unless they use a complex switch.
I am not saying this is not possible, of course, just that I can't imagine how this can be done.

[MWJB]

Observe the "language of the label", think of all those Scotch whiskies that elude to being a single malt with phrases like "pure" but aren't...

Class A/AB texture SIMULATION control - there is mention in a review of cutting 2 power tubes & boosting PI gain. I think by imagining how it is done you might be overcomplicating the issue as Peavey only claim to be simulating the/an effect.

Bias circuit is not an indicator of class of operation, neither is B+ really but it is a pointer to an ideal scenario.

If it sounds like it does what it says it does, irespective of whether it actually does it or not, I'm sure that will be enough for a lot of folks - even if it doesn't, it might still give a useful tonal palate. Probably best to give it a listen.

[Enzo]

The texture control is nothing more than a level control for ONE SIDE of the phase splitter.

The output cathodes are grounded, and the fixed bias supply is not adjustable. B+ does not change. The amp is very conventional.

[JC@]

I get the point..
The sound clips at Peavey's site show a nice sound palette between class A and class AB simulation, not my ideal amp though, but very interesting.

Would a pedal effect designed to "unbalance" both sides of the wave with a control and placed in the effects loop just before the PI, reproduce something like this?

Enzo, I understand the the fixed bias circuit could be made adjustable by changing the value of a resistor and adding a bias pot the usual way, right?

[MWJB]

Several harp amps have used various methods to unbalance the signal at the PI, I'm generally not a fan of the sound of the methods that I have heard (not heard the Peavey). Personally, I think that this often results in a loss of fidelity, dynamics and power. The resulting sound is often perceived as warmer...as long as you can live with the side effects.

John Kinder has a harp oriented pedal (AFB+) that has a feature that is claimed to have this kind of effect.

Quite popular routes with DIY harp players/amp tweakers include subbing the PI tube with a 12DW7 & deliberately mismatching plate current by 7-8mA (easy with an SF Fender, whilst monitoring current to determine a safe sweep on the pot).

[Enzo]

Yes, all those things do similar, and that is the sort of effect PV was going for here.

The bias supply is quite basic and would yeild to conventional modifications.

[JC@]

Thank you all.