[quote author="alk509"]I think it depends on the circuit... I've put TL783's in some tube gear, and I could hear a difference for the better. Then again, I think a lot of what people call "tube sound" has to do with the unregulated supplies found in most tubed boxes... I guess it's really a matter of taste. I have yet to do any real A/B testing with different circuits, but as soon as time permits, I plan to get to it.
When I was building the PSU for my
AKM78, Gus and Marik were adamant that I use an unregulated supply for sound reasons... I don't know about you, but I trust those two! :wink:
Peace,
Al.[/quote]
When I did a tube signal path but sand-supported design for an audiophile friend I had final passive decoupling at the tube plate loads etc. The regulators were mainly used to further reduce hum and noise because the low frequency path had a huge amount of gain. The big box was an electronic crossover and the woofer channels compensated for what is practically a free-air big woofer. It does make the speaker system less placement-sensitive for bass though, but oh the power required.
Even at that the regulators were quite a lot of trouble, and I wound up with a pretty complicated discrete design before things had good transient response, were robust, and were adequately quiet.
It's instructive to play with three-terminal regulators and see just how bad the transient response is. Hook up a power FET and a pulse generator and a load to the output and look at the response of the regulator. Of course it's worst-case---no real audio signals will challenge the thing as much as that---but it still shows how slow and ringy most simple regs are.
With a discrete design you can fine-tune the response to be more or less what you want. Again, usually not necessary, but it can be done.