More Circuit Design from the Archives

Going back through some old circuits I came across this circuit I designed back in 1999, 12 years is a long time in audio design, but I remember this fondly.
I built hundreds of prototypes, some just worked really well from the initial turn on, some tooks months to finalise, and some were just magic . And plenty were duds. This was one of the very good ones- a Directly Heated Triode Preamp, that is transformer coupled output, direct coupled between stages, uses uncommon DHT tubes.

The input tube is a 30, which  is a high gain dht triode, battery biased and directly coupled to the output tube which is a 33, a dht pentode, triode connected. It makes quite a respectable triode with low plate R - this gives the circuit low output impedance and will drive any power amp with excellent linearality.
The disadvantage with this preamp is both tubes are microphonic, something which has never worried me, I suspect it contributes to the euphonic sound of these circuits,but it freaks a lot of audiophiles when they hear the tinkle of a microphonic tube.
This design has aspects which are common to the DHT pres I build now, but they are much more evolved with different loading for the tubes, parafeed outputs, different biasing, fully shunt regulated power supply, etc, etc.
This circuit also works well with 71A DHT output tube, with adjustment for bias.
Still , most people would be very surprised by the sound, and I'm going to have to build another just for nostalgia.