I am the cover model for the triode mafia. All triodes, all the time!... Use a pentode, go to jail!... and then it happened... on one of the many long conversations dave and I have while working late night, the conversation turned to why anyone would ever use a pentode. We inadvertently made a list not only of what triodes do better, but also a list of what pentodes do better than triodes. The two that are very obvious and very big are that pentodes are several orders of magnitude easier to drive, and that they have lower distortion driving low impedance. Guess what? This is exactly what we need to drive an LCR RIAA circuit.
I have now compared in two different circuits - IT coupled (yes, IT coupled pentodes!) to an S&B 10k LCR and also nickel plate choke loaded and direct coupled to a teflon and nickel Intact Audio LCR. In both cases, it was not even a contest. I am a believer! Much more music! When you find yourself enthralled with the ballads of Art Pepper as much as the hard cuts, you know you have found it. Critical comparisons stopped being critical thirty seconds into each band.
So add phono to the list of things that I do not think will be revisited anytime soon. DHT linestages with nickel 1:1's and nickel autoformers - check! stacked supply direct coupled amplifiers - check! pentode phono front end - gasp - check!
oh.. and no wondering where the chassis style for this one originated.... It is funny though, as I originally built this phono years ago, long before I owned a WE7A. I guess I have been pulled this direction for years. Now to work out the Western Electric pentode input and tennis ball triode output version.
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You are reminding us that thinking outside the box is completely different than existing outside the box...way to go, Jeffrey!
ReplyDeleteBTW: pentodes also work really well in guitar amps :-)
Jim