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G6Tanuki · 14th Jul 2019, 8:36 pm

Practically, you need to consider what service your EL84 will be used in.

Simple single-ended Class-A - its cathode needs to be able to deliver twice the emission-current of its static-current, because if it can't you get 'clipping'.

If you're running a push-pull pair in Class-AB2 or well into proper full-on Class-B you may be only running 20 Milliamps of static current per valve, but on peaks more like 150 Milliamps - so your maximum cathode-emission needs to be good enough to handle this.

I built a bunch of guitar-amps and transmitter-modulators using a pair of EL84 and with proper AB2 biasing they could do 40W output for ages.

Though I rather preferred the 5763/QV03-12 because I could run a pair of them in near-class-C [static anode current 20 milliamps, peaking at 300mA at 350V HT] to give 50W and despite the anodes glowing they would survive for 100+ hours.

It was never Hi-Fi, we always had things TURNED UP TO ELEVEN!!!

14th Jul 2019, 8:36 pm	#16
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: Maximum cathode current for an EL84? Practically, you need to consider what service your EL84 will be used in. Simple single-ended Class-A - its cathode needs to be able to deliver twice the emission-current of its static-current, because if it can't you get 'clipping'. If you're running a push-pull pair in Class-AB2 or well into proper full-on Class-B you may be only running 20 Milliamps of static current per valve, but on peaks more like 150 Milliamps - so your maximum cathode-emission needs to be good enough to handle this. I built a bunch of guitar-amps and transmitter-modulators using a pair of EL84 and with proper AB2 biasing they could do 40W output for ages. Though I rather preferred the 5763/QV03-12 because I could run a pair of them in near-class-C [static anode current 20 milliamps, peaking at 300mA at 350V HT] to give 50W and despite the anodes glowing they would survive for 100+ hours. It was never Hi-Fi, we always had things TURNED UP TO ELEVEN!!! Last edited by G6Tanuki; 14th Jul 2019 at 8:55 pm.