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417A

Hi njjohn

The 417A (or its electrically equivalent 5842) is an 9-pin, wide bandwidth, low Rp, high-ish gain, IDHT triode that is supposed to present the tunes pretty decently. It is fairly commonly used in phono-stages, line stages, and driver stages of power amps. It has also made an appearance in a spud amp or two. They are popular drivers in DIY amps, where their co$t is less relevant and are suitable for two stage SET amps - Steve Brown, Thorsten and a few others have schematics floating about.

Gordon Rankin of Wavelength Audio uses them as driver stages in some of his amps. IIRC, he like a ~130V plate, 10mA bias (~ -2V at the grid) for these. They can be a b*****d to match between pairs - I think Gordon's designs now use a CCS in the cathode circuit to keep them matched? They have four grid connections and require some effort to prevent RF oscillations...

They sound like a pain in the a*s to use, are becoming expen$ive (especially if your require very close matching), but their reputation for good sound, gain, and low Rp are worth it for some.

Hope this helps

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