Those kind of changes can be expected depending on the tube. The Russian (Sovtek) rectifiers run a bit hotter than some of the others. It is still pretty well within spec for the tubes used.

Personally, I wouldn’t make changes to the biasing there. Biasing hotter (more voltage) gives you more headroom and more power, thus more volume (theoretically). But the tubes die quicker. Running these as you are describing is not really running “hot” as much as a but hotter than with the other rectifier so you are really in a good place with your measured levels.

Tube curves are a fun thing to get into. Here are a couple good sources:



If you havent read Blencowes book on Preamps, it is a great (best in my mind) resource. We still have some that we are offering with donations:

I have been able to pick up a few copies of Merlin Blencowe’s books “Designing Power Supplies for Tube Amplifiers” and “Designing Tube Preamps for Guitar and Bass”. Both are excellent resources for the tube amp builder.

As a way of supporting both the site and builders, we will give away the books for a PayPal donation. We have limited numbers available, but we can get more if necessary. Right now, we will offer BOTH books for a $70 donation. If you check on Amazon, the price for both books is around $80 pre shipping. We will include shipping for the $70.

If you are interested, click the “Donate via PayPal” button on the sidebar of the site. Once our quantities run out, we will have to reorder so be patient if we have strong demand.