I did consider damper tubes, at first, but weighed a few pros and cons. I would need dual dampers in order to fit it all in a hybrid bridge, so that narrows down the choices as most dampers are singles. I considered 6CG3 compactron first because it is the only damper available that goes to 350mA, but that puts it right at the limit with no derate headroom in case I want to up the PT to 400mA some day. Another big consideration is that 5AR4 is still in current production widely used in guitar amps. Once I build this I can easily swap out the PT for one rated 400mA, so the rectifiers would have to exceed that anyway. In the end I settled on using parallel 5AR4 for all these reasons in a hybrid bridge, just install two tube sockets. As for timing, the B+ will arrive well later than the bias because I've found the 5AR4 tube to warm up certainly much slower than a DH rectifier like 5U4, plus they are more compact. But yes dampers were my first thought but the mechanical space I have is driving a lot of this. Space is also why I chose to try all toroid, we'll see how that works out as I dont think I've ever seen anyone use a toroid choke as an PSU input choke. Space was why I abandoned using the monster sized Hammond 193MP choke in favor of toroid chokes. That is why I figured I'd put a 400mA rated center-potted toroid as the input choke, a small 0.1 capacitor in front of it might help it from getting too punished, I wont know until I get there. I keep updating the schematic against the mechanical design with each space compromise I encounter. I just updated the schematic to reflect the fact that I will be able to fit eight DC link capacitors, four 52mm pin spaced ones and four 37.5 mm pin spaced ones, whether I use all 8 or not is up for grabs but I am keeping the schematic in synchonization with the mechanical design.
Last edited:
My last build was meant to be compact, but felt like trying to squeeze a quart into a pint pot. I had the top plate, which had had the main holes cut, and wooden case, but it was a continual battle to arrange everything to fit in the space, and still be maintainable so things like bias changes could be managed.
In some ways it has dampened my enthusiasm for another project. It felt like 1 day soldering, 6 months fettling. I did use layout diagrams and 2D drawings, but did not go to the level you have with 3D representations, so hopefully you will have less challenges along the way.
The worst part about a beautiful and complex solution like yours is that as you get closer to the end of the project, you become incredibly leveraged in terms of mistakes on the metal work side. Screwing up the countersinking of the last machine screw can ruin the appearance, negating a lot of work.
In some ways it has dampened my enthusiasm for another project. It felt like 1 day soldering, 6 months fettling. I did use layout diagrams and 2D drawings, but did not go to the level you have with 3D representations, so hopefully you will have less challenges along the way.
The worst part about a beautiful and complex solution like yours is that as you get closer to the end of the project, you become incredibly leveraged in terms of mistakes on the metal work side. Screwing up the countersinking of the last machine screw can ruin the appearance, negating a lot of work.