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[bikerhifinut]

Originally Posted by Richard

Hi Andy, we're following with interest, please post pics if poss

Re the valves, ECC81 and 88 were Radio/TV types, and 82 and 83 were low and high mu audio amplifiers. 6CG7 is similar to ECC82 but has a different heater arrangement, 6.3V only for controlled warm up when series wired, and uses twice the current (you probably know that but it may affect psu arrangements). I've not used it but do like ECC82 which has many plug'n play varieties such as 5814, 6189, CV4003 etc which vary in tonal quality but most sound good

Yeah a bit of research seems to throw up that the ECC82 was a bit of a "Do it all" valve, used for frame and timebase oscillators etc and driver stages.
The ECC88, I already had figured as it was developed as a VHF RF amplifier, giving better performance than it's predecessors. That they work well as an audio valve is a bonus, however I am given to believe that Microphony can be an issue as with a lot of RF valves as it wasnt so much of an issue in the rf and if stages of a radio/tv set. Some seem to be more prone than others.

In a line level preamp I wouldnt expect microphony to be such an issue, its microphone and the first amplification stage in a phono preamp where I imagine the issues would be more apparent.

The trouble is, valve types can be a bit "marmite" some love certain types, some don't like em so I say go with what you prefer cos that's the right one.
The ECC81 seems to be a case in point, I think its a great valve in a lot of applications but there are a lot who don't rate it. Shame as generally speaking they can be very cheap for good NOS.

ECC83.............. I have tried many types and in the end I think you have to go a long way to beat the JJ ones as supplied in the WD kit. I got hacked off with "NOS" mullards after sepnding a bit in the past on them only to find that a lot had a tendency to either fail (heaters) or go noisy/microphonic. I think theres a lot of "NOS" touted about that were reject quality back in the day.

Andy.