This preamp is realisation of many ideas that had been floating around, about the "best" way to do things. The aim was to exclude semiconductors, feedback and electrolytic capacitors, series switching connections and potentiometer wipers  from the audio path and power supply. The result is a preamp with valve rectification (EZ80), shunt regulated HT supply (12BH4, 12AX7), anode follower input (ECC81), and SRPP type of output (ECC88, E88CC, ECC288). It also incorporates some unusual (or just odd) features because I wanted to see how they performed. The output stage gain is set by 5k1 resistor after the output decoupling caps (20uF). The input selection and volume control are both shunt.

Inspired industrial design, fully LVD compliant etc. No I didn't have any small children when I built this device!

The inside, OK so it does have an electrolytic in, but that was a later addition, and it is before the inductor. There is quite a thump (about 10 volts) on the output when the neon strikes, pulling the HT into regulation. This necessitated the fitting of an output muting relay. This was valve driven (ECL80), but took a heavy load from the HT and caused the transformer to buzz.
P.S. When I look at it now, there is probably a less radical mod that could stop the thump. At the time a valve controlled muting circuit was a challenge!

The shunt input selection and volume control aim to remove any mechanical connection from the direct audio path. It is always lossy, but if you put some valves in the box as well, gain comes for free. The absence of large decoupling capacitors on the first stage anode supply leads to a loss of channel separation at low frequencies. Further low frequency misbehaviour occurs at the output. The output frequency response is OK, but when measured on the inside of the output capacitor it rises as the frequency drops, leading to some compression (at 10 volts output) on normal music when large bass is occurring. Oh yes how does it sound? Above reservations noted (not a problem in normal output levels) what can I say, it is good, so so good. Clean, fast, effortlessly transparent, beautiful to listen to, and I know it sounds silly, but the authority and completeness with which the input selection and volume control work is uncanny. If it is so good why don't I use any more. Two inputs can be a limitation, and, new directions were calling....
P.S. In the future I intend to resurrect this circuit an use it with the 1MHz output stage...