Are you familiar with the EAR HP4? I rolled mine with NOS RCA's. Dead silent background with high or low impedance cans, and with high or low sensitivity headphones. The problem with the HP4 is that it does not drive planars as well as other amps I have in house, The LCD-3 and the HE-6 sound very nice when paired with the CS-600 rolled with NOS tubes. Then again, the planars have low sensitivity and not subject to the somewhat infamous Leben headphone hum.
Edited by Dr. Roberts - 4/12/13 at 8:31am