VVR on EL34 push pull

[JoeK]

I've tried a search here but didn't find anything relevant. I'm doing a cathode biased EL34 30 watt amp. I've seen the half-power triode switch setup but I was hoping to find anyone who has tried to scale the power on a pair of EL34. I've used a vvr on an 18watt amp with just the PI and PA scaled so I'm wondering if I could replicate the same on a pair of EL34. Any advice or experience would be great.Thanks in advance Joe.

[fyl]

Same everything except thermal dissipation. You may have to heatsink the mosfet.

[Diablo]

I used the alternative, Variwatt from Skipz circuits, on a Tweed Twin clone (5E8A circuit). I'm also running EL34s in it instead of 6L6 tubes. I am using the fixed bias version of Variwatt which adjusts the bias voltage automatically as you dial the B+ down. The cathode biased version would be simpler, but should also work fine. I don't think it matters what type of output tubes you use. I built this amp about a year ago and haven't had any problems with the Variwatt.

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