headphone amplifier


2015-03-15 5:11 pm
hello to everyone,
i wanna make a headphone amplifier. Propably the sapphire headphone amp. I wanna ask your opinion about the pass-trough circuit i wanna to make. Because the amplifier will be connected between my preamplifier and active crossover i need a pass-through circuit. The tube preamplifier will be connected to the headphone amplifier and via the pass-through the signal will continue to the active crossover. I have thought this 2 options:
1.When the headphone amplifier is off the input is connected to the pass-trough output via relay directly. When i power on the amplifier then the pass-through output is connected to ground via relay and after while the input is connected to the headphone amplifier board. With this configuration when i power up the headphone amplifier the speakers will be muted.
2. the rca input connected directly to the headphone amplifier pcb and the pass-through output. With this configuration the main speakers will not be muted.

what configuration would you prefer? The second one is simplier (there is no need for 2 relays neither for a circuit to activate the relays) but the preamplifier output will be driving the headphone and crossover input simultaneously. The crossover input impedance is about 20k and the headphone amplifier input is about 100k ohms. The tube preamplifier output signal pass through a capacitor and then through 2k2 resistor. I think that it can drive the both inputs simultaneously, can't it?
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