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Re: 8417 SOS

Posted by unclestu52 (D) on January 5, 2007 at 11:26:00

In Reply to: Re: 8417 SOS posted by Webnick on January 5, 2007 at 08:40:43:

The QS 8417 amps are standard push pull designs and the 8417's are fully utilized. You have misinterpreted the design of the QS amps. The earliest 8417 models use a 7247 input, IIRC. It is a dual triode which has half of a 12AU7 combined with half of a 12AX7. When those tubes disappeared, QS switched to a separate AU and AX7 tubes of which only half was used. A modern design, the 8417 needs little drive to reach maximum power and is quite sensitive to input circuit design and stability.
GE 8417's are great sounding tubes but when run in ultra linear operation tend to have high grid emission. QS solved the issue by running lower filament voltage (5.9 volt, IIRC). The tube is also very stable if the screens are run at lower voltage than the plates.

Stu

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