Which valves?

[Baggy Trousers]

On the old site I mentioned having a quartet of NOS Tung Sol and the new Russian equivalents. They really are equivalent with, in my judgment, the Russian variants being every bit as good as the prototypes when used in the Ka/Kit 6550.

You won't do better with the output valves.

Richard.

[Richard]

Originally Posted by Mike G

Hi guys,

So any more ideas? I'm sure there were alot more posts regarding valve upgrades on the old WAD site, I don't really have to go back there and trawl through all the old posts! Only really interested in vaves for WAD KAT6550, and PreII.

Many thanks.

Mike.

Hi Mike,

You're right but that amp was a few years ago now and most of it has been tried and done I guess.

I had Kit88 and tried at least 6 of each 6au6 (inc RCA, Tung Sol and Mullard ef94 etc) and ecc82 and 4 KT88/6550 types.

Best for me was Sylvania JAN 6au6wc (maybe same as Philips US production) Mullard box anode CV4003 (ecc82) and Svet 6550C.

I've tried several ecc83 makes in 2 other amps and like the near-equiv 5751 (GE) as being more natural and open sounding.

Rich

[Black Stuart]

HI Richard,
I only wished I'd bought 3, instead of 2 EH 5751 for Phono11, they really are better than the standard valve and as I've said elswhere - why did'nt WAD design Phono11 around this valve - it's exactly what you say. I will have to look for the best place to buy some GE ones any ideas anyone?

I also take back what I said about EL34s, I made a few small changes in Angela's KEL34 and it does sound very good indeed now, using Svetlana EL34.

Black Stuart

Richard, Stuart,
I agree on the 5751's - I've used these in my PhonoII for a long time now and they are clearly clearer! I can't remember where I picked up the suggestion but it was a good one.
NickG did mention that the different electrical characteristics of them (compared to the ECC83) may be making some difference to the RIAA curve, but I like their sound however it is being achieved. I recently tried some cryogenic Chelmer ECC83s (also comparing to standard and uninspiring Chelmers) and they came close but the GE5751s went back in.

I also agree about Svetlana EL34's, when I had my old AI s500 amplifier I first 'upgraded' it with some Mullards and then bought the Svets as 'spares'. After listening to the Svets I sold the creamy Mullards and enjoyed the clearer and punchier new production valves.

The first rule of tube-rolling though, should be try to try before you buy!

[Black Stuart]

Matt,
I think that WD could do far worse than build a Phono stage around this 5751 valve, which would of course mean that the RIAA curve would be correct.

Black Stuart

[NickG]

I think the 5751 is close enough to not worry about it.

[Bizzie]

When I tried a pair of 5751 in my phonoII it hummed constantly but there did seem to be a sweet sound if you could cut through the hum.

Anyone any ideas why I would get a hum if they've worked ok for others.

[Black Stuart]

Bizzie,
what did you use for the driver valve? I have used Svets 12AX7 (too warm and cuddly), EH 12AX7 slighty harsh sound but the best yet with EH5751s' and Tung Sol 12AX7 detailed but somehow wrong and no bass but there was no hum at all with any of them.

As you probably know the 5751 has more headroom but lower output. Does your Phono11 have any special features and how have you earthed it?

Black Stuart

[Bizzie]

My PhonoII is built pretty much standard I used a mullard ecc83 yellow print as driver valve and have two more in it now and it doesn't hum with any other valves I've tried just the 5751's.

The 5751's were used when I got them and I didn't pay much for the pair maybe its the valves at fault I'll have try them in my mono blocks if I can remember where I put them.

Nick,
Thanks for the reassurance about the RIAA when using 5751s in the Phono II.

Stuart,
I think that WD could do far worse than to 'inherit' the WAD Phono II kit and sell it!

When I stuck my MC Txs in (the Lundahl 9206s), I wired them for 20x, so any loss in gain when using the 5751s is not noticed as my Phono is still quite a bit louder than my other sources. I can't guess why you got hum with them Bizzie...?