This was the first incarnation of my KT88 mono-blocks. The artistic rendition arrived in my email as a complete surprise from Steven Spicer (see links page, Kiewa Valley Stereo). I had sent him the photograph and he was moved to do this! Steven is the author of the excellent "Firsts in High Fidelity", the products & history of H.J. Leak & Co. Ltd. Published by Audio Amateur Press, ISBN 1-882580-31-1
60 Watt triode connected KT88 mono-block. The power bandwidth is 10Hz to 50kHz. The drive topology is two DC coupled long-tailed-pairs, 6SL7 and 6SN7. The second pair features Shunt Regulated Push Pull active loads. I have dubbed this topology Differential SRPP Pair (DSRPPP). I have not seen it published before. Separate vacuum tube regulation is provided each for the drive stage, output stage and negative rails. It accepts both balanced and unbalanced inputs. The output transformer is a Bartolucci Model 106 (now Model 555).
Pictures show the "parts kit" ready for assembly to the chassis. All circuitry was pre-build as sub-assemblies. The right hand picture shows: Top left, DC heater regulators; lower left, high tension regulators; right, amplifier.
Click here to see Amplifier schematic:
Click here to see Regulator schematic:
Click here to see PSU schematic:
I wrote an article on this amp for VTV magazine which they were apparently keen to publish. It never was - no reason was given. Click here if you want to read it.