It is worth the trouble,in my opinion.With an adjustable bias you can use any tubes you want,you are no longer locked into paying more for current production tubes because someone "rated" them to work safely in your amp.Doing the mod is fairly simple if you know your way around the inside of an amp.You must locate the resistor on the board that sets the negative voltage.You then replace this resistor with,I like the multi-turn cermet trim pots,a pot of about 2x's the value of the resistor you replace.For example,if the resistor is 10k,I would use a 25k cermet pot.Connect the wiper of the pot to one outside leg and use the other outside leg as the 2 connections.Set the pot in the middle,which will put you close to what you have and then you have enough range in either direction.If any of what I've said here is not clear,it is probably best to take it to a tech to do it.It shouldnt be too expensive,Ive done a lot for no charge when doing a cap job on Boogie amps.


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