UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 120W PP EL34 amplifier re-born.

bikerhifinut · 22nd Oct 2018, 4:57 pm

Lovely work Andy!
By eck you don't do things by halves.
Well I think that should shame me into rebuilding my baby EL34 amps a mere 35W! I was holding back in the expectation that the house would be "rebuilt" by now but I should have known better and its scheduled to start next march with the erection of a "tent" over the whole building while the roof comes off. So I have this winter in the garage (brrrrrrr) to do any project work rather than my planned warm and dry upstairs study/work room.
Mine won't be as complex as yours, I'm sticking with tried and trusted "conventional" circuitry that I know will work and work extremely well. I will be doing the rework as an "all in one" stereo amplifier as we discussed earlier which should simplify matters. My main bit of nervousness is the need to use DC heaters on the EL34 as well as the signal valves due to the winding being 9V on that lovely big toroid of joes. Although I am tempted to bung in a separate 6V tranny for the power valve heaters maybe rated at 8A so that if I get a notion to redesign for KT88 types there'll be enough there. It'll be a heavy beast! I have a nice piece of aluminium here for a top plate but the main issue for me is not so much carving holes in that for transformers and valves etc but making the wooden framework for the chassis. I doubt I will be able to do rebates like you. Top marks!
A.

22nd Oct 2018, 4:57 pm	#28
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: 120W PP EL34 amplifier re-born. Lovely work Andy! By eck you don't do things by halves. Well I think that should shame me into rebuilding my baby EL34 amps a mere 35W! I was holding back in the expectation that the house would be "rebuilt" by now but I should have known better and its scheduled to start next march with the erection of a "tent" over the whole building while the roof comes off. So I have this winter in the garage (brrrrrrr) to do any project work rather than my planned warm and dry upstairs study/work room. Mine won't be as complex as yours, I'm sticking with tried and trusted "conventional" circuitry that I know will work and work extremely well. I will be doing the rework as an "all in one" stereo amplifier as we discussed earlier which should simplify matters. My main bit of nervousness is the need to use DC heaters on the EL34 as well as the signal valves due to the winding being 9V on that lovely big toroid of joes. Although I am tempted to bung in a separate 6V tranny for the power valve heaters maybe rated at 8A so that if I get a notion to redesign for KT88 types there'll be enough there. It'll be a heavy beast! I have a nice piece of aluminium here for a top plate but the main issue for me is not so much carving holes in that for transformers and valves etc but making the wooden framework for the chassis. I doubt I will be able to do rebates like you. Top marks! A.