There is also the Z-man Analog Signal Enhancer (ASE) which uses a single 12AX7, has a decent power supply (not a wall-wart like the MF X10-D) and an on/off switch. I've used mine in some high-res systems with very good results. Currently I use one in a system with Magnepan MG-12s and an InnerSound ESL amp. They can sometimes be found used for $90 to $120, but I don't think they are currently in production.
Passive tube stage/non-DAC device?
Happy holidays to all audiogoners...looking for a passive tube stage device to add a more analog "rounded" nature to my CD source...happy with my present built in DAC....any thoughts? thanks...