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G8HQP Dave · 16th Jul 2011, 1:38 pm

Half an ECC83 is available, in the form of EBC91/6AV6. Just ignore the diodes.

Pentode partition noise is mainly white, with only a small 1/f part. As a result, the noise advantage of triodes at RF is not so obvious for audio. That means that an audio cascode is little better than a pentode. Most valve 1/f noise comes from the cathode, so affects triodes and pentodes in the same way.

A pentode should normally be used with g2 decoupled, otherwise it is not acting as a pentode. Comparing a pentode to a cascode, the V1 anode/V2 cathode corresponds to somewhere in the electron stream, and V2 grid corresponds to pentode g2. Pentode g3 does not have a cascode analogue. Most pentode g3 provide little screening as the pitch is too coarse.

16th Jul 2011, 1:38 pm	#36
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: Triode vs Pentode Half an ECC83 is available, in the form of EBC91/6AV6. Just ignore the diodes. Pentode partition noise is mainly white, with only a small 1/f part. As a result, the noise advantage of triodes at RF is not so obvious for audio. That means that an audio cascode is little better than a pentode. Most valve 1/f noise comes from the cathode, so affects triodes and pentodes in the same way. A pentode should normally be used with g2 decoupled, otherwise it is not acting as a pentode. Comparing a pentode to a cascode, the V1 anode/V2 cathode corresponds to somewhere in the electron stream, and V2 grid corresponds to pentode g2. Pentode g3 does not have a cascode analogue. Most pentode g3 provide little screening as the pitch is too coarse.