What about the input tube ((12AX7)) on the M180’s? I’ve heard it can have a pretty significant impact on sound. Any recommendations on that one?
@500homeruns It does. That’s a fun slot to roll because it’s so easy (one per side, no re-bias). I used MANY on Apollos over the years. Best sounding tube was Mazda (also branded Cifte, Belvu) silver plates 12AX7 if you can handle a little extra energy on top. When I had daker sounding speakers these were divine. DON’T get the Cifte 5751 silver plates, these are brightness cannons.
For a bit of a warmer sound I really liked the GE 5751 TM BP "silver clips" version from ~1953. The later 50s non-"silver clips" TM BP are good too but not quite as magical.
Teles are relatively plentiful (used) and sound really good, just a tier below Mazdas. The ribbed plates are similar to Mazdas. Smooth plates are a little warmer. Most RCAs tend to be a little warm, but not like Mullards. Once in a while a run into an (oddball) obscenely bright RCA which surprises me (in the trash they go).
Various RCAs and Mullards are pretty good, I just preferred the above. Mullards are very warm and "thick" sounding if you need that.
You can even throw in a 12AY7 for something different. I had a red label GE that sounded pretty good (1963 / 64 vintage on red labels).
But you know what, I actually think the Russian re-issues sound really good and offer different tonal balances across the sub-brands. Mullards are warm (like real ones), Tung-Sol a little energetic up top, Gold Lions in between with a nice touch of sweetness.
The good news is most tubes will sound really good and give you a (slightly) different perspective. It really boils down to personal preference and system balance. I had a few dogs (usually just too bright and lean), but they were by far the minority.