Phono preamp tube rolling.

Mulveling 

I figured the last tube was  a cathode follower  or how could you get away with a 12 ax7 output impedance into the next stage.  Well  you and Lewm at least  helped him out with  there is a huge difference  between  12au7 and 12ax7.  The 12at7 in the middle.  Explaining how tubes work and how to read their data sheets,  is really  not  what he is looking for.

Enjoy the ride
Tom

IME, Mullard preamp tubes are best. They are hard to find but worth it. I got 12 12AT7s from a collector. Upscale may have some.But they are rare.

@tomwh The ares manual suggest that switch between 12au7, 12ax7 and 12at7 in case to play with the gain…. I did it successfully with no any problem.
My priority is listening to music and I’m not really interested in deep technical details of the tubes, it’s required lot of time. maybe I’ll explore this when I’ll retire… for now I just want to listen and roll, listen and roll :)…to figure out what I like the best…when I’ll be interested in tech questions I’ll post that… my current post is about something else as you could see. 

Andy at Vintage Tube Service in Michigan.

i was hoping @mulveling would weigh in also, he has a wealth of experience and some great phono stages as well. Where did you end up w the Herron ? 

on ARC , i got some serious hours out of the 6H30 in my REF5se, but keep changing the oil !

Fortunately, these small signal triodes tolerate a lot of abuse and can still sound”good” while being abused, if you don’t measure anything and are subject to listener bias. Which is all good. But it’s best not to draw conclusions like A is better than B based on a blind substitution of one for another type. If you think it’s fun and rewarding to tube roll, I submit its even more fun if you do some reading to gain a better understanding of what you’re doing. The science is fascinating.