Biasing amps that can't be biased...

[JonnyScaramanga]

I snapped the standby switch off my Peavey Valve King recently. It was the second time this has happened. It's not the best aspect of the amp's design.

While I was getting it repaired, the amp tech pointed out that the amp is seriously under-biased. Peavey make them that way so that they are really reliable, but it means I'm not getting much out of the power valves.

And Valve Kings don't have adjustable bias, so you can't easily change this.

Apparently modern Fender valve amps are the same. He said he's had great results fitting an adjustable bias to Fender Bassmans and Deluxes, and biasing them correctly.

He says he can do this to the Valve King for not much money too.

Anyone had this done?

[M1979]

unless one tube was getting really hot i wouldn't worry about it tbh.

i bought matched pair of el 34's for my tsl and they worked fine with out having to be biased and in the manual for my messa it says something like just buy good valves and it will sort it self out

[Sporky_McGuffin]

I htink the Mesa manual probably says "just buy Mesa valves". The F-50 one did. All sorts of justification guff that I didn't pay much attention to.

[imperial_black]

Originally Posted by JonnyScaramanga

I snapped the standby switch off my Peavey Valve King recently. It was the second time this has happened. It's not the best aspect of the amp's design.

While I was getting it repaired, the amp tech pointed out that the amp is seriously under-biased. Peavey make them that way so that they are really reliable, but it means I'm not getting much out of the power valves.

And Valve Kings don't have adjustable bias, so you can't easily change this.

Apparently modern Fender valve amps are the same. He said he's had great results fitting an adjustable bias to Fender Bassmans and Deluxes, and biasing them correctly.

He says he can do this to the Valve King for not much money too.

Anyone had this done?

Ive heard of people getting this done before.
The thing is what is it about the power valves that you want to change?
Do you want it louder?
Peavey stuff generally is pretty reliable the VK sounds great ,you could probably bias it up a bit without losing too much reliability but I'd wait for biasing problems to crop up before modifying that part of the amp.
Mind you is not like its an expensive amp so its no big deal.
How did you manage to snap the switch?

[JonnyScaramanga]

Originally Posted by imperial_black

How did you manage to snap the switch?

First time it broke in the back of a van on the way to a gig.

Second time it mysteriously broke itself. Seriously! I turned it off one day, and when I went to turn it on the next, I found that I couldn't.

I think I will get it biased up. I don't think there's much point in having a valve amp if you're not using the valves.

[imported_timmyo]

I've heard of folk having that kind of mod done to amps. And also heard of folk having a single internal bias pot turned in to a pot per power valve with external test points to save pulling the chassis out to do it, and not need to have matched valves.

<edit> by the way - I read your 'final' column - got anything else in the pipeline ? I'm sure any replacement columnist will not nearly so rock-n-roll hair . . .

@Sporky : yes I've heard Meas'a 'save a few pence on components and justify it technically' approach derided by amp-sniffers a few times.

[Sporky_McGuffin]

Originally Posted by imported_timmyo

@Sporky : yes I've heard Meas'a 'save a few pence on components and justify it technically' approach derided by amp-sniffers a few times.

In one respect I like it. You know exactly what valves it is you need to buy. No faffing. And the amp certainly sounded good, so it can't be that terrible an approach.

[JonnyScaramanga]

Originally Posted by imported_timmyo

<edit> by the way - I read your 'final' column - got anything else in the pipeline ? I'm sure any replacement columnist will not nearly so rock-n-roll hair . . .

Cheers Tim! I didn't know that was out yet. Yeah, I hope that I'll be in GT again at some point. I've got some stuff running in Total Guitar at the moment, but you'd have to read it with a magnifying glass to spot my name.

The main thing at the moment is my originals project... Demos online soon (yes, I've been saying that for a year, but I'm in the studio on Saturday, so it will happen!).

[imperial_black]

Originally Posted by JonnyScaramanga

I turned it off one day, and when I went to turn it on the next, I found that I couldn't.

That's exactly what happened to my car on new years eve accept I couldn't turn it off.

[imported_timmyo]

Originally Posted by Sporky_McGuffin

In one respect I like it. You know exactly what valves it is you need to buy. No faffing. And the amp certainly sounded good, so it can't be that terrible an approach.

It's bollox though - their valves aren't any different so that they work right - the amps are simply biased cold so that any will work. And their workshop procedures are to only replace the dodgy valve - not as a pair on warranty work, so they'd come back unmatched anyway. It's a cost thing - pure and simple.

I agree though - if it sounds good and it doesn't break, then all is good. But they should have the balls to say so, not put some fluff in their manuals.