For as long as I've been using a pair of HD600's I've been using a first generation Earmax Valve headphone amp to drive them (lovely combination).
But as I've now gone n bought a new pair of HD600 I thought it was high time to change the valves as well.
10 years is a pretty long time to be running valves almost 24/7, but then these kinda small pre-amp valves aren't driven anywhere near as hard as valves in a power amp. All in all they've lasted pretty well!.
This is a pic of the old tubes out of the unit:
http://www.musicprogressive.com/images/valvechange.jpg
..and the new valves in place:
http://www.musicprogressive.com/images/newvalves.jpg
The new tubes are all Mullard tubes, the outer ones ECC86 made in Holland, and the central one a 12AT7WA made in the UK. Powering on new valves for first time is always bit unnerving, hoping not to see any nasty blue flash or other unusualness. But they powered on clean with nice orange glow to the rods inside.
Instant noticeable difference was that everything sounded more solid, the top end a lot more focused n less hissy and even the bass seemed to extend a bit more (I'd read opinions of old tubes sounding more bassy, not in this case). A not to dissimilar improvement to what I noticed from comparing my 10 year old HD600 to the brand new pair.
Overall very pleased with the sound, just wished I'd changed them sooner now!
