The Magnificent Lamm Amp
The are small amps, there are large amps, there are stereo amps, there are mono amps, and then there are Vladimir Lamm's ML3 Signature two-chassis monoblocks, demmed at FSI with Verity Lohengrin speakers, a Lamm L2 Reference preamplifier, LP2 phono preamp, NeoDio CD transport and DAC, and Kubala-Sosna cables, and Critical Mass Systems racks.
The ML3 Signature runs a single Russian GM70 directly heated output tube (introduced in 1948, the year I was born) with 1200V on the plate to give 28 watts into 8 ohms. The GM70 is driven by four paralleled 6N30P "Super Tubes," with a single 12AX7 as the input stage. The choke-smoothed power supply in a separate chassis uses four 12AX3 diode tubes as a bridge rectifier to derive the high-voltage rail for the output tube, with another two 12AX3 tubes supplying DC to the front-end tubes.
Listening to Louis Armstrong singing "Blues in the Night" from LP, I auditioned the amps with no negative feedback and just 1.2dB of negative feedback. You wouldn't have thought it would make a difference, but darned if switching in even this minimal amount of feedback—which, in theory, should make the amplifier perform better—didn't diminish the enormous sense of space on the recording.
Oh, the price? Each pair of ML3 References costs upwards of $130,000 and takes two weeks to manufacture.