Headphone amp for Sennheiser HD 560S (120 ohm) using readily available and cheap Toroidal transformers for power supply. A 50VA 55 + 55 volt with series connection for 110volts is sufficient and the filaments can be driven from an 80VA toroidal with 12Volts via LM317 regulators. The distortion (Simulated but not measured) is of the order of 0.04% at 10khz and mainly second at 1 Volt out. Power supply noise is un-auditable. The amp will run into 60 ohms ok but the distortion goes up a little. Sounds excellent.
Attachments
Some notes. Schematic developed in Microcap from ideas from Tubecad posts 297 (Bastode) and post 504 for output. C3 was left out but does reduce distortion very slightly in simulation . Q2 needs to be on a reasonable sized heatsink as it is running at 2.5 watts. The 2 x 56K plate load for ECC82 can be replaced with a single 27K at 1 Watt. My implementation used all half watt resistors hence the use of 2 x 56K. C5 and C6 only see about 40 Volts BUT for safety I would use 250Volt for all capacitors.
