Howard - I know that you no longer sell Stax equipment but you did say in an archived Q&A I saw on the internet that you were prepared to answer questions. Apologies if that is not the case. I have an SR-404 earspeaker that I use with a small solid state energiser (SRM-X). I note that most people seem to use an SRM--006T with this earspeaker. Would I get a significant benefit from upgrading to a vacuum tube energiser? It is not an inexpensive option.

I know all of the STAX items you mention very well indeed. If it were my money, and with the experience I have, I’d stick with the SRM-X for now. The reason being that it is utterly silent (or rather, my ones were) and in comparison with the 006t there is always a little valve ‘rush’ or ‘hiss’ in the background. This is not entirely eliminated even with the 007t. Such is the downside of valve energisers with electrostatic earspeakers.

However, there is a naturalness to the 006t sound which is quite seductive and very pleasing on naturally recorded music and speech which makes the SRM-X a tad ‘electronic’ is comparison.

I should point out that eventually nearly every SRM-X I sold went wrong after many years of faithful service and could not be repaired due to the unavailability of parts in general and the transformer in particular. A great pity as STAX never again built an energiser quite like the SRM-X.

In a nutshell then, no I don’t think you’ll achieve a significant upgrade currently. Therefore spend any surplus money you have right now on more music. Incidentally, I did not find the 006t Mk2 to be significantly superior sonically to the Mk1 version. Hope this helps.

Howard Popeck