UBER TUBER rev. 1 What are P1 and P2?

[Ariosto]

Hi, I cannot find in the PDF no information at all about these two trimpots. Should they be left blank?

Ariosto

[somnif]

They're the Plate bias resistors (they were static 100k resistors in the first board version, then changed to trims to give a bit more flexibility).

The info about them is on the first page of the document: https://www.madbeanpedals.com/projects/_folders/Tube/pdf/UberTuber_rev1.pdf

To quote the document:
The difference between the two versions is that rev.1 replaces the 100k plate resistors with 500k trimpots. This change was made in response to several builders having trouble achieving proper plate bias with fixed resistors. And, this makes sense due to the wide variety and age of 6111 tubes as well as being from different manufacturers.  With the trimmers, you should be able to dial in the proper bias voltage so long as you have a good tube. Rev.1 also changes the layout slightly

Other notes:  I've tested a wide variety of 6111 tubes now using a test circuit and there is a lot of variation in them. What I've found is that they are very forgiving in plate bias. When setting the new trimmers, P1 and P2, anything between 11v and 13v (Measured at TP1 and TP2) will give a good result. You can even go a bit higher and lower without issue. With all the tubes I personally tested getting about 12v on the plates was no problem. And, if you buy the UberTuber with an included 6111 tube it is guaranteed to work in the circuit.