You can't rebias this amp because it has no adjustment. You don't have to buy new JJs, you can find older tubes that are the same as the ones you like.Īnd the person who said you need to re-bias every time you change output tubes is just quoting things without knowing what is happening with this amp. Another option is to hunt down the same tubes that you like the tone of. If you like your tone better with the old tubes, put them back in if you like the tone and it works like you want. 14v should be reasonable for most tubes. Peavey must think it's design doesn't need to be this exact. But as Enzo said, they have been making non-adjustable bias amps for years. 14 volts may be perfect for some tubes and not so for others. Voltage is not an indication of proper bias, current is. The only way to be sure of exact proper bias is to measure current through the tubes. SO I am not suggesting you shouldn't do this. This is also in the PV mind when they design amps. Many people find their tone Nirvana there and more power to them, the tube life is whatever it is. But overall, the hotter they run the less time they'l do it. If you run this amp up to 70% it won t be the difference of 6 weeks versus two years, I can't say how long your tubes wil last. This is all well and good, but the hotter the tubes run the shorter their lives will be. WHen you make an amp adjustable, 99.9% of the time it is to run the tubes hotter. Others think 80% is better, and some would rather see 60%, and yet these are all OK bias levels. SOme guys live by the 70% rule - setting the bias current for tube pplate dissipation of 70% of max. There is bias way too cold, and there is bias way to hot (the tubes get red hot), but in between there is a wide range of bias currents that are perfectly fine. To some folks bias is almost a religious term. There is absolutely nothing special about the tubes, they don t pre-measure them or sort them. The factory stuck tubes in it when they built it - there was no adjusting done then. But the point is the amp sounds great to you now. DO guys decide to modify their amps? Hot rod them a bit? Sure, and to them the amps may well sound better. The PV philosophy is to design amps that work fine without having to be adjusted. That amp left the factory as non-adjustable bias. They tell you that, but do you do it? And yet your car drives safely down the road year after year. Well the tire pressure in your car MUST MUST MUST be checked every time you get gasoline.
Your guy thinks all amps MUST MUST MUST be rebiased every time tubes are changed. You are not being fed a line, but You are running into a philosophy. Self biasing often just refers to cathode bias. I am not familiar with what Traynor is doing.
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