Zesto Andros PS-1 Tubes

@Todd

Just seeing your post now. I recently found my manual and realized that while I had my pairs in the correct spots, I had the input and output positions confused.

I'm still using the Telefunken/Mullard box plate combo but have been thinking of digging out my pair of Amperex short plates. Your description of them pretty much mimics how they sounded in the MiniMax phono. I would imagine similar results in the Zesto Andros.

Rob, thanks for the update. I'm sticking with the Amperex/Mullard config for now.

One update to mention: The 2dB observed increase in gain might have been due to the Brimar's being weak. I installed them as NOS about a year ago but when I pulled them they only tested out at about 50%. Not sure what happened there. I did make the assumption the Andros was self biasing so maybe I damaged the Brimar's? Does anyone know if you need to re-bias the Andros when installing new tubes?

I thought you said it was autobiased. If you change the output tubes on an amp and it is manually biased ,that is when you need to bias the tubes. I never heard of anyone biasing small signal tubes. (I am sure there is an exception out there ...)
So are you happy? It sounds like the tube rolling addiction might have gotten to you. Be careful it is a slippery and steep decent. Best and good luck-

I'm pretty sure that there's no need or way to change the bias on the Andros. I've never had any tube gear that called for biasing of the small signal tubes, like Mechans said.

Sorry to hear your Brimars got tired-out prematurely. I think that my Cary line stage can be hard on tubes (6SN7) but I haven't noticed any of that with the Andros.

I do like what I'm hearing with the M8137 tubes now on the inputs and the Tele ribbed-plates on the outputs.

The Teles are very durable they seem to last forever. Did you get your ECC83 12AX7 = M8137 equivalent NOS NIB. If so it should also have a long life. I am wondering why your Brimar gave out so quickly even if it had a limited lifetime by measurement.
Did you try the New Sensor Gold Lion ECC83? I heard they were sort of Mullard like, sweet and melodious If you don't need all the gain of the 12AX7 you might want to try a 5157. I like them a lot, and now that the NOS and OS (Old Sh*t)12AX7 are getting hard to find.