What are your favorite tubes in the GOTL with your Aeolus?
The fun aspect to the amp is that your favorite can change often, and mine does, depending on what combination is in the amp. Mine has the configuration with 6 power tube slots, 1 slot for SN7-compatible tubes, and 2 slots for C3g-compatible tubes. Like many in the Glenn thread, I don't often use SN7 tubes in that slot anymore, it's almost always a pair of 6J5/6C5/12J5 tubes (with an adapter from
@Deyan ), sometimes glass but most often metal versions. My preference is for metal RCA's from the 40's (meatball logo) as those just sound very natural to me. But if I'm going for larger staging or separation, then it's Tung Sol or Sylvania 6J5 or 12J5, both glass. The Tung Sol's are extremely spacious and deep and have great realism. Those are some of my favorites for creating the "in the room with the musicians" sound. That said, I like the tonality of the RCA better.
For the C3g slots, I had some Mullard EL32's with adapters in those slots for months. This was the position I changed the least. But recently I have been going with a pair of 6J7's as they use the same adapters as the EL32. The only 6J7 tubes I have so far are RCA (meatball) and Sylvania, both types are metal. These tubes have similar characteristics to the 6J5-type tubes in their sound. So right now I'm listening to a pair of 1942 glass RCA 12J5's and a pair of 40's metal RCA 6J7's and I enjoy the tonality so much I just want to put my head back and enjoy. If I want to mix up this sound and get a bit of each, swap out the RCA 6J7's for Sylvania 6J7's. Or keep the RCA 6J7's but swap out the RCA 12J5's for Tung Sol 6J5's. The last few nights have been all RCA though and I'm not in a hurry to change it.
In the power slots, I used 6x 6BX7's for a while when I first got the amp. My favorite of those tubes are Tung Sol's, but they don't have as much bass as GE 6BX7's. The Aeolus has enough bass on it's own, so that's not really an issue. With the HD650 that has less bass, this doesn't work as well. A pair of Tung Sol 5998's works very well in these power slots, and like other Tung Sol's can give excellent clarity and staging. But they need the right 6J5's to balance that out. I'm not a fan of Tung Sol 6J5's with Tung Sol 5998's (it can be too much clarity, almost too sterile, but take comment to mean relative to other options, it's not actually sterile). This is even though I like both separately, when combined with other tubes. I have a pair of GEC 6AS7G's for the power slots. As highly regarded as they are, they're not my favorites, and I'm not sure why. I just can't get on board with them. Maybe I haven't hit on the right combination with driver tubes yet. That needs more work.
My favorite power tubes for the last several months are 6080's. I most often use Sylvania's from the 60's (right now I'm using a pair from 1966). Sometimes 2 of them and sometimes 4. They just seem to work with every tube combination I put in front of them. They are among the cheapest power tubes I have. The combined cost of the Tung Sol 5998's and GEC 6AS7G's could probably buy another pair of ZMF's, but I just use the Sylvania's more.
I think it's cliche in the Glenn thread, but the GOTL can make most tubes sound good, and sometimes favorite tubes end up being unpredictable, and not even necessarily expensive. Right now I have 6 tubes in (2x RCA 12J5 glass, 2x RCA 6J7 metal, 2x Sylvania 6080), and their combined cost was maybe $70. And it sounds awesome.
I'm not sure I actually answered your question, I think I just gave a rambling monologue
. It's a hard question to answer with the GOTL and Aeolus because you almost can't lose. Anyone thinking of getting either will hear nothing but encouragement from me.