Ultra High-End Transistoramp Sirrah V2.0
My intention was to build a one board design with low effort and a maximum of sound quality. Thus the idea originated to build this amplifier, sounding on the level of the Sirius V4 with reduced output voltage.
Connect the input to ground and adjust the output between +Out and -Out to 0V with R57. Now connect your voltmeter to +Out and ground and use R50 to adjust it to 0V. Now repeat these two steps again. Repeat this procedure after 20 minutes when the amplifier is warmed up.The amplifier is now adjusted and ready for use.
With a supply voltage of +/-200 Volt the amplifier can output more then 250 Volt eff. The power consumption of the amplifier is 30 Watt. A change of the environmental temperature of 20° C resulted in an voltage drift of 1 Volt at the output, that is nothing for an electrostatic headphone.
It can drive all STAX Pro headphones (580Volt BIAS), if you reduce BIAS to 280Volt it can drive all STAX headphones. Certainly you can drive other electrostatic headphones like KOSS, Sennheiser, etc too, just fit the BIAS to the desired value. The amplifier sounds very clear and detailed. The basses are dry and strong, the frequencies at the high end are sounding very transparent. With its very fine resolution the amplifier sounds on eye level to the Sirius V4. With the 250V output voltage you can reach 110 dB sound pressure with the most Stax head phones. That corresponds to the noise of a chainsaw in 1 meter distance.
distortion level at 100V: 0,02%
signal-to-noise ratio: 100dB
output impedance at 1KHz: 300 Ohm
frequency response (-3dB): 0 - 50000 Hz
power consumtion: 30 W