I built this pre-amplifier using the THEL VX-D modules for line-level amplification. The enclosure is made of a 90 mm thick chunk of layered birch ply. The bottom and rear plates are aluminum plates that were cut and engraved using a CNC machine. The custom-made source and volume control knobs were machined using a lathe.
The THEL VX-D electronics use a discrete MosFET output stage with a very low output impedance. This prevents high-capacitance cables and low-impedance power-amp inputs from affecting the sound signals.
The power supply uses rechargeable batteries instead of the conventional DC conversion from AC voltage derived from the wall outlet. This results in the cleanest possible DC voltage supply that is free of any hum or noise, which might affect the sound quality. The batteries are recharged automatically when the pre-amp is not in use to make sure the pre-amp is always ready to play.