I'm afraid Sage Audio is defunct - Les Sage passed away
nearly ten years ago. His designs have a good reputation,
although for obvious reasons you won't be able to rely on
any support from the company.
15 years ago there exists audio manufacturer Sage Audio (England), which produced amps and signal generators with very low THD.
From Sage Audio commercial:
Hi-Fi class A mosfet modules 50W to 250W pure class A
Sage Audio’s Supermos2 Modules, designed by Les Sage, features the most advanced and sonically accurate circuitry available today (1999)
class A circuitry throughout,
super fast slue rate for superbly detailed transients,
top grade audiophile components,
capacitor signature sound coloration eliminated,
totally distortionless constant IC VCE(?) circuitry, THD typically 1ppm,
advanced PCU feedforward ripple elimination,
localized feedback loops with extremely low overall feedback.
Sage Les 10p37 13p1 13p14 17p1 17p24
Active Loudspeaker Systems
Part 1 11p23
Part 2 12p4
Part 3 13p2
Minimalist Pre-Amp update 10p23
Nicam Stereo TV A/V Interconnects & the Scart System 15p16
Pre Amp Power Supply 1p9
Resonant Mode Mains Filters 16p9
Sage Super Supply 1p10 2p21 3p4 13p2
Satellite Radio 15p13
Star Earthing 2p12 3p3
Testing and Matching Active Components 17p7
The Syclops 5p5
Can't help you much - but I "built" an amplifier using the SuperMosII as an upgrade to my HY60 amps.
The unit failed on both channels after about 3 - 6 months of use. There seemed to be an internal short circuit - so I got a hammer and "Knocked Off" the potted circuit block off the heatsink and found that Sage Audio had not used insulators to insulate the output devices from the heatsink - but just relied on the aluminium anodising to act as an insulator. After short period of operation this "insulation" layer broke down.
I tried to "De-Pot" the unit using "Nitromores" the paint stripper, after a week or so got down to the PCB level, but don't start to reverse engineer the circuit.
The design used 6 Hitachi OPS devices and Zetex E-Line transistors. On "de-capsulating" the unit I found a cheap and nasty electrolytic coupling capacitor on the audio input.
I don't have any more information - but I wonder if the all the Supermos II modules where built the same way - without insulators, and they subsequently all failed? - if so, did the Stress lead to the untimely death of Les Sage? (may he RIP)
Its a great shame there’s appears to be no more information on these "State Of the Art Product" – even today, it would be great to see the memory of Les Sage given a second lease of life.
My greatest respects to a Great designer - even by todays standards,