Bare Knuckle Pickups Forum
Forum Ringside => Guitars, Amps and Effects => Topic started by: MDV on January 18, 2012, 05:57:49 PM
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I found two =C= EL34s. The valve fairy put them in my valve drawer and didnt tell me.
I will put them in my JVM410H
Its 100W, obviously.
Do I run it out of the same impedance as normal, or run it out of half impedence (4 ohm in this case)?
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Impedance ratios are FUN!
Ballpark figures, let's assume it's 5k ohms Ra-a with 4 output tubes to 4, 8, 16 ohms. Popping two tubes means you need to reflect 10k ohms to the primary because you've removed half the parallel resistance. That means your 4 ohm tap (5000 to 4 impedance ratio) with 8 ohms across if reflects 10k to the primary of the OT.
tl;dr - yes. Enjoy your Winged =C= growl.
EDIT: That's yes to half impedance by the way. Use the 4 ohm tap for an 8 ohm speaker.
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Thanks :)
TS;WM if anything.
Not afraid of technical exposition, dont understand a couple of terms in there, could do with a glossary, but i get the jist; for the valves to see the same load when running half your power amp you need half the impedence. Gotcha.
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Let's try an easy version then ...
* OT matches the high impedance of the valves to the low impedance of the speaker
* If four tubes need to work into a 5000 ohm load then two tubes will need to work into a 10,000 ohm load
* If your OT ratio matches 5000 to 4 ohms (on the 4 tap) then it will match 10,000 to 8 ohms on that tap