8417 amp

[KB5MD]

Has anyone retired an audio amp that uses 8417 tubes to use some other tubes that arent so pricey? That is rewired not retired.  I have acquired a nice McGohan amp but all the tubes are broken and they are 8417's.

[KF7WWW]

6550's, KT88's, KT90's... They all work in place of the 8417's..

[WD5JKO]

The 8417 was somewhat unique in that it has a very high transconductance...As a consequence very low grid swing is required, and a low standing bias. The other tubes likely need a higher bias setting, and therefore more peak grid driving voltage to fill out class Ab1 operation. Simply popping in a pair of 6550's without changing the bias will likely cause an overload with red plates.

If you have the room, and some flexibility in circuitry, perhaps look look at a quad of 807/1625's instead. These are still inexpensive, and will easily make 100 watts RMS audio for a quad in class Ab1. A quad of EL-34's is also a possibility as these are available new at reasonable prices.

Jim
Wd5JKO

[flintstone mop]

We had a nice Bogen PA that used those tubes. It rocked and rolled and made nice music in a Gas meter repair shop. There musta been 100 speakers hooked up to the amp and FM tuner. Then the battle began for rap music vs oldies but goodies. Then someone poured battery acid in the FM tuner. We removed the amp from the shop and installed a smaller amp and microphone so that the supervisor could page people who received personal calls during work.
Fred

[kb3ouk]

I've also read that 6L6s can be used in place of the 8417s, as long as you make sure that the bias and screen voltages are rightfor the 6L6, which I know requires more bias than the 8417, and I believe has a lower screen voltage as well.
Shelby

[w1vtp]

I'm have the same palpitations over a Bogen M60 that uses those tubes.  Also, an EICO ST70 that uses 7591s

The 8417s are unobtainium and the 7591s are expensive as he!!