In 2022 TubeSociety joined the shoot-out of the European-Triode-Festival in the Netherlands. A tube amplifier should be developed without an output transformer (so called OTL). We designed a special driver-stage with ECC88 with constant current load in the anode for lowest harmonic distortion. Within the constraints of the ETF a power stage with Mosfets was allowed. So, we designed our power stage with Mosfets closely behaving like pentode power tubes. The final result? Our new (no global negative feedback) tube-plus-Mosfet class-AB push-pull amplifier has a spacious detailed soundstage and is remarkably clean and quick with 50 Watts output power. This is exactly where we were aiming at. Please find all the details plus circuits in the description of the TubeSociety Project-2022.
The TS-2022-OTL mains transformer contains all the windings to power the Mosfet power stage and the special ECC88 driver section. See the short-specs below.
Power: 300 VA
Primary: 2 x 115 Vac
Sec.-1:190 V-ac / 100 mA-ac [ECC88 section]
Sec.-2: 22 V-ac / 6 A-ac [Mosfet power section]
Sec.-3: 22 V-ac / 6 A-ac [Mosfet power section]
Sec.-4: 6,3 V-ac / 1 A-ac [ECC88 section]
Sec.-5: 15 V-ac / 200 mA-ac [spare application]
Diameter: 125 mm
Height: 60 mm
Weight: 3 kg