Zesto Andros PS-1 Tubes

I lived with the stock tubes for quite a while and was very happy. I only swapped them out when I was chasing some noise gremlins (which turned out to be a preamp tube).

I started with a set of Tungsram-Austria labeled 12AX7's and a set of Telefunken ribbed-plates. Not bad, but seemed to be lacking something....maybe too much of a good thing. I swapped a in set of Mullard M8137's in the front positions since I was familiar with them and put the Teles in the back. This was a good pairing and one that I could live with - balanced without overemphasizing any particular frequency band.

I recently swapped out the front pair of Mullards with some GE 5751 TMBP that were a favorite in the buffer spots of my Minimax. Still plenty of MC gain using a DL103R. Probably a bit more focus.

I'd like to know the tube layout/function for each position. I'm assuming the front spots are the input tubes and the rears are the buffers. One reviewer mentioned swapping only one of the stock JJ's with a Mullard, so........

@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.

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.

@Mechans: I bought the M8137s lightly used from a fella who bought them NOS from an online dealer.. I think he had tried them in a Marshall amp and decided he was looking for something else. One NOS tube dealer that I've worked with called the M8137 "the un-Mullard like Mullard tube." The Teles I got from a seller here a while back so I would say they were ANOS, but tested really strong in my B&K 707.

Sorry to hear that Toddc's Brimars didn't hold up for some reason :(