Stax SRA-10S preamplifier / headphone amplifier. I added a Pro bias output to the amplifier, cleaned it up, adjusted it, and installed a contact cleaner on all switches and potentiometers. The preamplifier includes a phono stage and adds 10 dB of gain to the output of the already high gain speaker. However, it can be turned off from the front. Defective capacitors were also replaced. Only powered by 100 volts.