Anybody have any experience of these valves for hi-fi...???

[Cyndale]

Does your valve amplifier have auto or manual biasing? The Croft Series 4S has manual biasing for each valve. The EL34 setting is 60mV and the 6550 is 80mV. Biasing has a huge effect on sound quality!

Manual biasing, Its a Chinese R8 Willsenton and designed to take either EL34s or KT88s - there's a switch beside the mains socket to choose which you which to use. I also have an Airtight which really only likes EL34s but again is manual. I prefer manual biasing if only for peace of mind, after changing tubes I would check and adjust adjust for a couple of days afterwards.

I have enough 6550 valves which I started out with, I might just give them a try while I am trying to figure out where to get some EL34s.

I suppose EL34s/6550s/KT88s are a personal choice if they can all be used in the Croft!. From memory KT88s are a classical music lover's choice.