What cap(s) are you running for C2? I have tried the 120uF electrolytic listed in the BOM, a 270uF electrolytic, 2 100uF motor run caps incombination with those or stand alone. I was targeting at least 300uF for C2 but keep coming back to just the 2 motor run caps only. I would prefer a solution that uses less space though.
I have used multiple different combinations including nothing at all, just a bench power supply wired into the board with C2 removed so I could test at voltage level that would make my current C2 very unhappy. The listening tests over the past few days were done with a 120 uF 500 volt Panasonic electrolytic cap in the board and a 100 uF motor run cap in parallel. For space limited builds I usually use the biggest electrolytic that I can fit into the board and parallel it with the biggest polypropylene cap that I can fit under the deck. In my 45 based TSE that is a 40 uF 400 volt ASC cap that I got surplus. I have some polypropylene "Unlytic" caps that I bought from another used here many years ago that will find their way into my UNSET when I build it.
I am on the fence regarding if I want to build this as an integrated amp or as a stand alone for use with a pre. The SSE that the UNSET will replace is integrated with a volume pot, source selector to switch between the dac or phono, and sub out. The biggest problem with this setup is if my wife turns it off to watch TV the dac may still be streaming and signal will pass through to the subwoofer which can be very annoying.
When I had a similar setup in Florida I simply plugged all of the "HiFi stuff" including the powered sub, into its own power strip which was turned off for TV watching so the TV played through it's own speakers. The setup in my work room used a line stage which could be turned off to silence everything. I used it primarily as a buffer with multiple outputs, each with it's own volume pot so I could feed a common signal to one (or more) of several amps in my setup. I also had a box full of relays and switches to select one or more sets of speakers for each amp.
Other things I am thinking about is if the uNSET needs a fan and if it should have exposed tubes with those top caps.
I have 1 amp pico fuses wired in series with my 1 ohm cathode resistors. Yesterday I shut off the fan that blows air across my board and let it get hot for about an hour with no signal applied (worse case heat). The idle current will creep upward as the fets get hot which lowers their threshold voltage. I was curious if this could lead to a runaway condition. The idle current was set at 110 mA after a 5 minute warm up and it leveled off at 121 and 123 mA after an hour. The heat sinks were too hot to touch with readings between 70C and 84C with my $20 IR thermometer. The same thermometer shower readings of 240 to 260C on the glass of the output tubes near the caps. If real, this is a bit too hot, but I am running them at 40 watts, which crept up to nearly 46 watts over time. I think that some of the heat sink heat was IR absorbed from the nearby tubes. My other unfinished UNSET board will have the heat sinks on the bottom, but I will try using the chassis deck as a heat sink in a build, and add a finned heat sink to the top if needed.
I am not a fan of fans, but it is possible that I use one here for entirely different reasons than hot heat sinks. When I lived in Florida there were three people living in the house, myself, my wife, and my daughter and two cats. All were taught to respect electricity, that it could kill you dead, and cook your body to a crispy state if touched. The door to my workroom was closed whenever I was not there, and there was this big red killswitch button on the corner of the bench which depowered everything in the room except for the lights and computer. The bench was "hot" only when I was there. By high school my daughter was in the marching band and a house full of kids armed with musical weapons was not uncommon. They knew that the workroom was off limits and that stuff in there could kill you, but all of the amps and musical gizmos that they played with came from that room so it was respected. I made guitar amps for the kids that wanted one, which helped in the respect department.
Today I have 4 grandkids. They do NOT know about, fear, or even understand high voltage electricity. This is prevalent in today's "YouTube and TikTok generation" where stupid deadly stunts seem commonplace. People are often seen playing with live electronics, and most of that is relatively harmless 5 volt or 12 volt stuff. We also see videos of people poking around in a live microwave oven, or using a microwave oven transformer to burn wood which recently killed a couple and burned down their house. Unfortunately there is rarely any differentiation between these two extremes given.
Again, my entire workbench is cold whenever I'm not there working. Potentially deadly things like my UNSET test board have its power cord removed when I'm not working on it. I do this out of habit since I got zapped a few times from simply yanking the cord from the power strip. All power cords are black and it's too easy to unplug the wrong one. Anything built for use in my basement workspace must be "grandkid proof" which means insulating them from high voltages and hot tubes. That's the real reason my 845SE amp has remained cold and up on a shelf. It has exposed 1050 volt wiring on both chassis and 845 tubes that get real hot. Now that I have UNSET, I'll probably part it out or sell it for parts.
An UNSET based amp, and a push pull big brother or two will find their way into the rack of equipment that is part of my computer based music workstation. There is already a rack mount PC in that workstation which contains multiple fans. The UNSET that I make for this workstation will be rack mount and probably be built into a rack mount PC cabinet, so the enclosed tubes and top caps are a given. A PC fan or two may be used to direct tube amp heat out the back of the rack so it doesn't cook everything above it in the rack.
If I build a conventional looking tube amp it will have a cage over the tubes. The cage will probably be a wire office basket from Ikea, Walmart, or a thrift store. To cage or not to cage is a decision best made depending on your use case. Kids, cats and anyone not understanding the danger must be trained not to go near an uncaged amp, or protected from touching it. It took two years of blasting kitty in the face with a water gun to train him not to go into the work room. Did that keep him from jumping onto my turntable in the living room when it was in operation? No, it resulted in the destruction of a Garrard Zero-100 in the mid 70's which turned out to be a good thing since I bought a Technics SL-D2 which I still use today.
