(20-10-2023, 09:01 PM)Murphyv310 Wrote:(20-10-2023, 07:29 PM)Jez Wrote: I design hi fi equipment as the day job, using valves as well as solid state BTW, so I'm familiar with the likes of the EF86. A pretty useless valve actually. Low noise compared to what? other very noisy pentodes? I've never found a use for them in audio!
Hi.
Well that's a statement and a half! So what would you consider a low noise valve? The EF37A was considered a low noise valve but what is the benchmark you are using to make comparisons?
All pentodes are useless as low level low noise valves. That is kinda the point. An ECC88 in cascode will give at least as much gain and way lower noise. A decent ECC83 is pretty low noise and no slouch mu wise. Most low level valve circuitry back in the day was pretty rubbish really so I guess they got away with the EF86 and at least the spiral filament helped with hum. They didn't appear to know that resistors generate noise for a start and you will see things like 1M in feedback or EQ networks or shunt feedback RIAA with a resistor of 22K -100K ish in series with the magnetic cartridge
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