The BCF receives a balanced input signal and converts it to an unbalanced output. It is a unity-gain buffer that offers a high input impedance, a low output impedance, low distortion, and great CMRR. In addition, because the BCF uses a push-pull topology, its use is not limited to line-stages, as the BCF can be used as a headphone buffer-amplifier if the headphone's impedance is high enough (say, 300-ohms).
Aikido Line Stage Amplifier Kit (9-Pin & dual-mono)
Custom Aikido Line Stage Amplifier Kit (Octal & dual-mono). Select only what you need: tubes, resistors, PS and heater bypass capacitors, two types of coupling capacitors (PIO and film), printed circuit boards, ceramic tube sockets, and board stand offs.
Due to popular demand, the SRPP+ is back, minus the power supplies. The new PCB is 6in by 5in and, like all GlassWare PCBs, is crazy overbuilt, with extra thick double-sided PCB material and heavy 2-ounce copper traces. Each channel gets its own large power supply RC filter, whose voltage rating can be a low 250Vdc, perfect for high idle current applications, such as headphone amplifiers; or, 400Vdc, perfect for line-amplifier use. The SRPP+ PCB holds pads for two sets of output coupling capacitors. All in all, it's a fun little board and I can imagine many different audio applications, from the input stage of single-ended amplifiers to headphone amplifiers for high-impedance cans, such as those offered by Beyer and Sennheiser.
12Vac SRPP HPA holds two hybrid SRPP headphone amplifiers. The output stage is actually a small power amplifier in its own right (a Zen single-ended amplifier). It consists of one MOSFET that is loaded by a constant-current source, which is made up of an LM317P voltage regulator configured as a constant-current source. A two-resistor negative feedback loop sets a gain of 1 (unity) for the inverting output power amplifier. Each channel sees a 200mA idle current flow, which is enough to deliver 3Vpk of output voltage into 16-ohm headphones and twice that into 32-ohm drivers. Of course, it can also easily drive 300-ohm headphones.