Is Amp re-biasing strictly necessary? Fender '68 CDR

colourofsound

So my '68 CDR is coming up to 3 years out of the factory and I think in an attempt to lower its noise I will do a complete re-valve in the next few months.

The question is (since Fender amps tend to be biased cold) do I really need to get the amp biased? Sure, tweaking for the best sound is one thing, but from an amp safety/longevity point of view, can I just swap Groove Tubes for JJ's and go happily on my way?

Cheers!

menamestom

I would, it should be pretty easy to do with a DMM.  If it is anything like a Princeton Reverb, it will have a pot and test points, you just get he schematic and set the MA rating between 2 points.

Longevity might be affected if the bias is too hot, but I suppose if it sounds okay when you swap them it should be broadly in range.

I suppose it's like buying new tyres and not getting it balanced, the car won't crash but it may not drive its best and the tyers may wear out quicker.

jpfamps

Your amp should be fitted with Groove Tubes (which could well be JJs, they will be labelled GT-6V6-S).

If you purchase Groove Tubes with the same rating number then you will not need to rebias the amp.

Of course you will pay extra for this.....