Vintage Yugoslavian made 12ax7 tubes for ARC

I have been using the Ei 12ax7 ( Thor T1000 mk2 ) for years and the trick to them is to find a good tight pair..Some of the later ones don't measure and or last very long ( but still sound good )and if you can find some of the 70's Vintage they are noted to be one of the best of the
Ei's...They are crisp,clean, and airy ( as described )and extremely transparent...Very nice sounding tube..Not overly warm,but for me just the right tone.......

It has been said that those tubes were made on the retired Telefunken machinery. Of course there is alot more to a good tube than what equipment poops it out. To me, they do resemble the ribbed plate Telefunkens in sound but aren't as good overall. Not a rich or warm 12ax7, but very good in the right application like phono preamps - a total absence of bloat and smearing of the signal. Very fast, detailed and transparent. A great value when they were current products, not sure what they go for these days. Remember though, a good Tele can cost close to $100.00 now.

I use "Yugo" tubes in a couple of pieces of equipment. They are also known as EI and were made by EI.

There are more than one model 12AX7. The one most folks refer to has a long grey plate and is modeled after a Telefunkin. A very nice clean/clear balanced tone but I wouldn't like it, I think, in a system already on the edge of brightness. It wouldn't warm it up much.

The other I use has a short(er) grey plate which has a little less high frequency energy and a more mellow tone. Each type serves a purpose and it depends on the equipment as well as synergy with other stuff in your system.

FWIW.