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Old 22nd September 2017, 06:14 PM
bikerhifinut bikerhifinut is offline
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Join Date: Jan 2006
Location: Penrith, Cumbria
Posts: 828
Default Re: My Cathode follower with active load.

Another thing springs to mind Bob.
You are using "gold pin" ECC88, I guess that means they are specially selected or even (if the older mullards) specially manufactured to close performance tolerances and matching between the triode halves. I think some of the older E88CC were like that too although now i feel the "special quality" claims are bandied around fairly randomly on newer production valves.
Anyway, I think this means your ECC88 are actually working bang on their design parameters, the resistor values are right on the money, broskie supplies exact values not just preferred values. Whereas the Russian valves may be a rebadged 6N1P or something and also perhaps not so well matched between triode sections.
Something to ponder on Bob and would explain the evidence of your ears?

As I remember it, the ECC88 was never designed to be an audio valve, it's intended home was in the front ends of VHF receivers. This would suggest matching of triode sections was fairly low down on the priorities although it was designed to be suitable for cascode use? And again, a valve with capabilities at VHF frequencies could well be oscillating up there and perhaps this is why your russian ones sound harsh?

I believe your findings Bob, and I hope my amateur attempts at explaining your Experience make some sort of sense?

Andy.
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