Owner's Manual

7
5. Output section mode: Solid-State / Tube / Tube+
The Pro iDSD Signature is a one-of-a-kind product that is able to switch between:
'Solid-State' - a purely solid-state J-FET based circuit of fully-discrete Class A topology.
'Tube' - the J-FET circuitry is switched to the valve Class A section based on 2 x GE5670.
'Tube+' reduces available negative feedback to a minimum. As a result, a greater amount of
the tubes natural harmonic distortion is produced (even order harmonics dominate).
When switching, there is a momentary pause as the circuit switches over.
The audio circuit is a development of iFi's revolutionary 'TubeState' design. It is fully-discrete,
fully-balanced with either tube or J-FET input switchable, bipolar second stage and mosfet-bu-
ered bipolar Class A power stage (with Class AB for low impedance headphones and very high
levels). The circuit is fully DC coupled.
Please note that, due to the wear on the cathode of tubes after an extended period of time in
solid-state mode, the tube heater element will automatically power down and turn o the tubes. If
the tube heater is shut o when switching to tubes, they will need to warm-up again (as if the
whole Pro iDSD Signature itself was powered up from cold). Music will continue to play via the
solid-state section until the tubes are ready.
This ensures maximum longevity for the NOS General Electric 5670 tubes.