Based around the Russian GM70 high voltage directly-heated cathode triode vacuum tube, our Russian importer Misha Kucherenko (right) commissioned these custom build monoblocks from David Manley in 1995. Only 6 pairs were produced, and Misha bought them all.

These amps were a Single-Ended design exclusively incorporating Japanese TANGO transformers and chokes. The B+ ran at around 1200 Volts DC. I remember one our technicians, Richard, using two Fluke meters in series in order to measure the rail!

One each 6SN7 and 6SL7 were used for the input and driver tubes. An interstage transformer coupled the input and driver stages through the paralleled driver tube's cathode to the output stage. While no global Negative Feedback was deployed, the input and driver tubes were surrounded in Negative Feedback taken from that driver-cathode to the first triode's cathode.

Here is a scan of one of our hand-drawn drawings documenting the physical layout for the builders.

And here is a photo of a crazy GOLD Manley system in Russia featuring 4 pairs of these rare Manley GM70 Single-Ended Triode amplifiers, a Manley 300B Preamplifier, a Manley Reference DAC from the 1990's and a gold plated Manley Massive Passive equalizer.