I am so enjoying the ZMF Auteur on my solid state amp (Monolith 887), it sounds great, but I just could not ignore Zach (ZMF's owner) and many other ZMF users that they sound fantastic on a good tube amp. That meant some research, and I decided to talk to Glenn of Glenn Studio. He is a builder of tube amplifiers, on a custom basis, you can choose exactly what you want. I chose to order an OTL amplifier with some recommended upgrades. For me that includes:
A Lundahl transformer, two 6AS7 type output tubes, two 6J5 drivers instead of a 6SN7, and a rectifier tube, Gold Point stepped attenuator, Jupiter coupling capacitors, and XLR input/outputs.
I know many here don't think much of tubes, but the Glenn amps get a ton of love, including from ZMF, which is saying something, since they sell a different brand. When they go to Can Jam and other shows, one of the setups they use to exhibit what the ZMF headphones are capable of, they include a Glenn amp.
Glenn stays way busy, so I am on the waiting list. It will probably be a long wait, so I'll have to be patient. In the mean time I will just enjoy my current setup, it is producing excellent sound, so being able to compare them will be fascinating.