The slight method to all this madness is that I want to take my developed designs and then make some PCBs. The whole ethos of these designs is that they will be cheap to build using 12V LED SMPS power supplies and the DC-DC buck converter, and that they will operate from any line voltage because SMPS, much like the honey badger, don't give a shit. The cost of both of those is less than £10 combined on ebay. A 2U rack chassis is £30-40.
Enough babbling, here are some pictures.



Since I intend to run some pretty high gain preamps up in this bitch, I'm going to use a MOSFET gyrator choke to clean the power supply right up as the DC-DC boost converter can sometimes add a little bit of chirp. Something like the circuit below will attenuate PS noise above 100 Hz by ~70 dB for very little voltage drop!

I'm on lockdown from work a the moment due to COVID-19 so as long as I have enough bits in my inventory I should make pretty good progress on this quickly. The final part of the puzzle is the output buffer. Usually I'd opt for a high voltage MOSFET (IRF820 or similar) here, but this time since I have a convenient 12V supply I'm going to use an opamp. I have a bunch of TL074 quad opamps so I intend to use one channel as the buffer, a second 2 channel active baxandal tonestack to simulate presence and depth controls (https://sound-au.com/articles/eq.htm - fig 5). I have 2 left over so one might be used as a mid boost and then the final one as a voltage follower to buffer the master volume to output. This is all low voltage stuff and can be breadboarded outside the chassis while I find what I like.