Alright everyone, I have the next big modification to my franken-crack ready. Meet the tube-rectified bottlehead crack! I completely re-implemented the power supply with an oversized power transformer capable of supporting a tube rectifier. The high-voltage winding is maida-regulated for a consistent, stable, low-ripple B+ voltage no matter what rectifier is plugged in. Any 5V rectifier is supported. I've tried 5U4G, 5U4GB, 5AR4, and 596 rectifiers with great success.
One neat thing here is that if I wanted to go back to SS rectification, I can! I have a SS plug-in rectifier that fits in the octal socket. This was tons of fun, and I learned a lot about power supply design in the process!
Under the hood you can see the maida regulator for the HV winding, as well as the massive heatsink attached to it. I managed to fit this while keeping all the previous upgrades in place, including the onboard DAC.
I also replaced the input wiring with shielded cable, as there were now AC lines closer to the input wiring. With the shielded wire in place, the amp is completely silent with no hum whatsoever from the new PT. It's silent using both the RCA inputs as well as using the onboard DAC.
Overall I am very pleased with how this turned out. The differences in sound are noticeable, and my BHC has never sounded this good! Aesthetically, it came out better than I expected too. I managed to fit the new transformer in such a way that it covered the massive hole in the top plate from the original transformer.