[Radio Wrangler]

Aye, Andy.

THe problem with valves is that when you want to up the power, you either have to parallel a number of devices and then get worried about matching and current sharing, or you are forced into higher power devices running much higher HT. Scary HT.

I wonder if it's a case of keeping the cathode current and area within bounds where they can be sure of the current density being shared well across the area?

The directly heated nature of a lot of the powerful beasties is another inconvenience.

I keep suggesting 3-500Z to audiophiles. Triode, check!, directly heated, check!, looks the biz, check! Anything that looks like that ought to sound awesome, using their logic. But really, I'm just thinking of the top cap anode connections and the kilovolts they sit at and the possibility of thinning the ranks of the audiophiles a bit.

I designed my last valve amp in the early 1980s. Lots of TV line output valves in parallel with two groups operating as a totem pole output stage, DC coupled, no output transformer. The stereo pair was monstrously big, but it was done for a purpose: To investigate the differences between no-holds-barred designs based on Valve, Bipolar and MOSFET technologies. It served its purpose and the bits got recycled for other purposes. I couldn't hear any difference between the three when I didn't know which was in use. I thought I could when I did know but that was probably my own suggestibility. I tried other people. Some musicians, some audio hobbyists, some uninvolved people. So the Mosfet beast has sat in my living room, beside one of the speakers for over 35years. It just works, and works well enough that I don't feel any need to go further down that path. I was comparing three no-holds-barred designs each having had no corners cut or costs saved. I wasn't comparing a complex semiconductor job against a minimalist valve job.

That said, I think designing a reasonably acceptable valve amplifier is a good deal easier than designing a comparably acceptable transistor one. But when you account for component availability I think it's a skill worth acquiring..

For me, hifi should be fun but some other people take it far too seriously. There was a quotation of a Mr Shankley after someone had said that football wasn't a matter of life and death "No, it's more important than that." was his qui, but he had a sense of humour. It's the people without that which worry me.

So, if your 807 amplifier is just for the hell of it as a learning exercise, then go for it!

David