The SR-71 ‘Blackbird’ is a full-featured two channel tube preamp in a pedal with two truely independent channels. Each channel has it’s own dedicated interactive Bass, Mid and Treble controls. The clean channel is based on the classic ‘Blackface’ circuit Leo Fender developed from the RCA Receiving Tube Manual. The overdrive/distortion channel is a hot-rodded 4-stage tube clipping circuit that can create symmetric and/or asymmetric tube clipping distortion. Both channels are 100\% tube analog, operate at 250V and feature true bypass switching.
An external switch allows biasing to be selected for 12AX7, 12AU7 or 12AT7 tubes installed in the overdrive channel. Internal bias trim pot allows further adjustment for other types of dual stage miniature B9A tubes such as 12AV7, 12AY7, etc. Swapping tubes allows the fundamental character of the drive channel to be altered to replicate a wide range of vintage guitar amps. The Blackbird has two output jack sockets. One is a tube buffered output for connection to guitar amplifier. This output is a low impedance tube cathode follower stage with +10dBu of gain and is capable of driving long cable runs with lowest possible tone loss. The second output is a Jensen C12N speaker emulated output based on an analog inductor/capacitor circuit. This is a discrete buffered output with +20dBu gain allowing direct connection to mixing desk, PC sound capture card, low imepdance (down to 8 Ohm loads) headphones or power amplifier. The Blackbird is built to last and for rigorous touring – each preamp pedal is meticulously constructed and tested by the designer, Phil Taylor. Polyester capacitors and instrumentation grade resistors are used throughout the circuitry which is housed in a tough powder-coated aluminium alloy enclosure.