I built my first tube (pre)amp using a couple of 6GU7's I had laying around and a cascode design from https://www.diyaudio.com/community/threads/franks-ultimate-tube-preamp.12042/. The original design was for 12BH7A and a complex power supply but since it was pretty low power, I built a full DC tube preamp using a VDC 5 amp wall PS. For the 305 VDC power, I used a $10 high voltage boost converter from Amazon and a cheap LM317 voltage regulator for 6.3 heater voltage which is heatsinked to the chassis with a piece of bar stock. I did several stages of filtering to clean up the high voltage and had to play around with what the converter liked but it is dead quiet. I found a 22uf capacitor followed by an inductor and some 330uf caps (which I repurposed when I upgraded my Wilsenton R8) was the best combination. The heaters are DC and can be either 6.3 volts for the 6GU7 or ~12.6 for the 12BH7 (I added a switch not shown). I am using this like the color preamp Skunkie built on a class D amp and it greatly improves the sound. I need to add a power switch on the front and I have a nice LED pushbutton sitting on my bench. I cleaned up the paint job by adding a couple of white pinstripes. I'd like to clean up the wiring/layout of the power supply filtering a little. I was also wondering about adding a bypass capacitor on the bottom tube with a switch but it sounds pretty good as is.