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The chassis will be all .125" Aluminum, no steel other than transformer laminations and bolting Yes, I will use a thermistor for a soft start and all of my caps will be rated for around 100V over no load B+.
I'm fortunate to have a group of local diy builder friends who are designing and building amazing sounding transformer coupled tube amplifiers. Two techniques some of them now implement is to attach a sub-chassis to the top plate made of Delrin that they attach the delicate input/gain stage and tubes to (and sometimes the output stage). The damping of the Delrin reduces vibrational and microphonic energy that will be carried to that section if mounted directly to the metal top plate. It requires drilling slightly larger holes in the top plate as the tube sockets will be mounted a bit below the top. The second thing they have been doing is to add a dedicated transformer and power supply just for the input section. Apparently, no matter how large the main power supply is there will be voltage fluctuations and sag feeding the input section, which needs very consistent voltage supply. With these two changes added to otherwise existing amplifiers they have taken their builds to much higher performance levels. Don't know if you're familiar with these techniques but thought I'd mention it since you're at this early stage of your build.
Thanks for the ideas Rusty. I am familiar with the pros of having the tube sockets suspended from a dampening material, I just haven't seen delrin used that way. I would think it would get to soft with the heat in the chassis and droop over time....
Single ended class A with a proper power supply and solid state rectification shouldn't have a problem.I know someone that likes to use Delrin for the top plate.
The 211 is a different world from an EL34.
Look, the EL-34 amps I posted pictures of (p/p) are one of the amplifier pairs that recently added the independent input supply. I didn't know it had been done, was very familiar with the sound of the system prior and when I visited was really impressed by how much better it sounded. When I asked what changed, he showed me the addition to the amplifiers. That was the only change. Since then, these builders have incorporated this into any new amplifiers they build and added it to existing amplifier pairs they had on which there was room. I'm not sure if you've tried these suggestions in your own builds and they were unsuccessful, or if you're in the camp of "I've never tried it but I can't believe it will make a difference, therefore it's a bad idea." The OP asked for suggestions for additions to his new build, I responded. Apologies to you for the annoyance.
Have you bounced your design off the members at diyaudio.com? They have no shortage of opinions, but there is some real expertise there, too...
Thanks, these irons looks nice. Edcor use M6 at lower price and Hashimoto use Hi-B.
I orders some custom wound OPT from Thermionic Labs. They will be 20 watt OPTs with 5k primaries and both 8 and 12 ohm secondaries. A 42% CT and air gapped for 80mA each. If you want to order the non-custom spec, here is the website with the specs. https://www.thermioniclab.com/en/single-ended-output-transformers/single-ended-5k-4-8r-20w-ultralinear-output-transformers-pair-1.html
