First Test for tube bias on ARC Ref 110?

It really depends a lot on where you got your new tubes and how well they were matched. That said, I test the bias a couple hours after replacing the tubes. Then about every 25 hours for the first 100 hours or so. The tubes will usually drift as they break in. How much they will drift really depends on how they were matched. Tubes that were purchased from ARC will probably drift a lot less than tubes from Joe's Guitar store.

The amp is brand new and the tubes are the KT-120's included from ARC. Sounds like I should probably start checking them now. They have about 54 hours on them at this point. Thanks for the feedback.

It's surprising that Reference models of ARC do not have an auto-bias. Even if the most primitive autobias circuit is implemented, you don't have to worry about biasing for at least half of tube life. I don't clearly understand ARC philosophy beyond that.

It's surprising that Reference models of ARC do not have an auto-bias. Even if the most primitive autobias circuit is implemented, you don't have to worry about biasing for at least half of tube life. I don't clearly understand ARC philosophy beyond that.

The ARC sound is highly resolved, open and transparent. Any additional circuitry that does not advance those goals (or worse yet that detracts from those goals) is not included in their designs. Convenience vs. sound quality I guess is at the core of their thinking. That is my best guess at their thinking.

I would check the tubes to see if they have drifted a bit. Then I would check them maybe around a hundred hours.

I also own a Ref 110 but I don't use ARC tubes. ARC burns their tubes in a bit before they are matched. This tends to make the matches much better than tubes that are factory matched. The Ref 110 is an excellent amp. I have owned mine for a few years now and it never ceases to amaze me.