The Signal Transfer Company is the only source for PCBs guaranteed to comply with the power amplifier design philosophy pioneered by Douglas Self. The crosstalk performance of preamplifiers, and the linearity of power amplifiers is often defined by the fine details of PCB layout. An apparently minor error can have dreadful effects on performance. Our PCBs have been designed with meticulous care at every point. The board layouts are precisely the same as those approved by Douglas Self when his famous series of articles appeared. You can therefore be confident that in some respects at least, proper operation is "built-in". We supply the finest quality fibreglass PCBs, double-sided with gold-plated pads. All boards have full solder mask and a silk-screen component layout. Each PCB is supplied with extensive constructional notes, previously unpublished information about the design, and a detailed parts list to make ordering components simple. A range of kits of parts to build our PCBs is now available: kits contain all parts including machined heatsink coupling plates for the power amplifiers. Douglas Self is available to answer any questions relating directly to Signal Transfer products. He can be contacted at: If you like to keep an eye on Douglas Self's website, you will know that recently it has not been available at its usual address of dself.dsl.pipex.com, nor at aqpl43.dsl.pipex.com. It has now been permanently rehomed at: douglas-self.com

The Signal Transfer amplifier power supply provides a high-current power supply for feeding two of our power amplifiers, combined with closely regulated +/-17V supplies at 500 mA for powering op-amp circuitry, including the Low-Noise Balanced Input Card, and the Amplifier and Loudspeaker Protection Card. Available as PCB, kit, or fully built and tested.

The Compact Blameless Power Amplifier. A small-format Class-B power amplifier card that will fit into minimal space when the full low-impedance load driving capabilities of the Load-Invariant Amplifier are not required. in every other respect this design has all the features of the of the other amplifiers we offer, and it gives the full Blameless performance into 8 Ohm loads. Available as PCB, kit, or fully built and tested.

A comprehensive amplifier & speaker protection card that provides relay muting and guards against DC offset errors that can destroy expensive speakers almost instantly. It also gives a slow turn-on and fast turn-off to mute power-up and power-down transients, two channels of over-temperature protection, and a shutdown input. Available as PCB, kit, or fully built and tested.