Pre3 Valves

[david]

Hi,
Does anyone have any knowledge of the valves and the effect of the hi above ground potential voltage lift for the heaters in the Pre 3 (and 2)?

I’ve had one ECC82 go very noisy whilst I’m still effectively doing running in hours and I had the same issues with the Pre 2 and PCC88s before until I replaced the valve with a Mullard NOS ECC88.

I half remember something about the high voltage breaking down the cathode insulation……..does that ring any bells anyone?
Thanks
David

[Richard]

Hi David,

The heaters are raised to protect the cathode on the last ECC83 section of Phono. This is a cathode follower and runs at 110V on the cathode. In fact ECC82 and 83 are specced at 180V max h-k so it really is protection rather than essential, perhaps depending on valve manufacturer.

(The voltage raise may have been inherited from KLPP1 which, I think, used an ECC88 as cathode follower and does have a lower h-k rating of 50V, but I don't have that circuit to confirm.)

Anyway, the raised voltage won't be the cause of your problem on any of the 2/3 modules.

What will be the cause, if your exp is like mine, is those JJ valves with the short plates that look like ECC88. Bin them.

I first had one JJ ECC82 (Tim dP branded) go noisy in a new Ear 834L 2 months ago. Then a month ago in WD Pre3 (JJ branded). Then, lo and behold, after 4 years of light use, a week ago, a JJ ECC83 (Fender branded) in our Fender twin amp.

All the same symptoms; a sort of feathery rustling sound like it was trying to tune in a radio station at idle. Swapping for a different valve fixed it instantly. It was also noticable that the different ones were quieter, as in less hiss, apart from the rustling.

Rich

[david]

Thanks Rich. Which ones do you recommend? I tried some NOS RCA ones from Parts Connexion and they were rubbish: much lower gain and more mcirophonic than a microphone.......
David

[Dik Dolan]

On Richards recommendation, I bought a pair of "ECC82/CV4003/M8136/Mullard" from Watford valves a while ago, and they sound excellent in my pre3. Price was about £25 each I think, plus vat and p&p... not cheap but to me, worth every penny.

[david]

Oh Mullards again! They are brilliant-but expensive!
Thanks

[Richard]

Yes the Mullards are nice and a bit cheaper here,

http://www.langrex.co.uk/sales.html

Also look at their GE5814WA (ECC82) which are a dark bargain for £5 and the RFT ECC82 for £8 which are a little brighter sounding.

For ECC83 in Phono, the EI at £6 are storming, not for the faint hearted, absolutely full-on.

Rich