Thank you!
The Agartha 2021 is an incredible piece of kit. I’m blown away every time I listen, especially with how resolving the are with the Elrog 300Bs
Don’t expect to roll as much as you did with the Pendant, 6AX5 (full wave rectifier) doesn’t have much impact on the sound. I’m not sure if that’s because of the rectifier itself or the fact that most (about 80-90%) were all made by RCA and rebranded. There are 2 types of construction but they didn’t have a huge impact on sound swapping between the two types IMO.
Unless you plan on rolling 300B’s that just leaves drivers to roll. Luckily there are a lot of options and drivers impact the sound significantly just like the Pendant
However the Revision 2 moved to a Noval front end (12A*7 and equivalent). I didn’t find these to be the best match for 300Bs. Justin did it in an effort to lower the noise floor. 12BH7’s worked well IMO (increased current makes these similar to ECC99, designed to drive 300B amps) G37-R is great too but not as outstanding as it was in the Pendant. I wouldn’t recommend a revision 2, I would look for a 2021 with the octal front end. 6SL7/6SN7 are just plain better in this amp (plus all the single triode equivalents 6J5 & CV6/VR135 really open up the possibilities for tube rolling). Octals have a wider, holographic stage and a more lush, romantic sound. Novals sound narrow and flat in comparison.
All that said, this amp isn’t without its quirks. Noise floor is one (3x higher noise floor than the Bigger Ben). Red October has a lower noise floor but it’s also twice the price. This is only an issue on the 300 Ohm tap, running 6SN7 (or single triode equivalent) fixes this for ZMF dynamics. Running a pre-amp also helps with this (and adds to increased dynamics as well)
All in all it’s an underrated amp, I don’t know of too many owners out there. It’s certainly not of of the top choices for 300B amps but now that I have mine dialed in I wouldn’t part with it. Not sure if you’ll be able to find a 2021 though, the one I bought was the only one I ever saw come up used.
Also it scales every headphone very well. ZMF Dynamics in particular sound incredible. It gave a new lease on life for my VO