Scrap PA Amplifier

Since I do work in schools it means I get access to some old equipment. One of many is PA equipment. I knocked off some old PA speakers from work that we're meant to be thrown out but haven't been. I wanted to used that but couldn't. The reason I couldn't is that these are CV speakers that run off 100V RMS and those amplifiers aren't all that common to find (cheaply at least). With this in mind, I went to build myself an amplifier to run it.
It is made from a cheap Jaycar amplifier kit and a transformer. The kit has an 8Ω output at around 1W. I fed the output into a PA transformer wired in reverse ie power into the secondary. With the transformed wired up in this arrangement, I get about 20-180V on the lines. This can drive it pretty well but distorts easily and with the volume, all the way up overdrives the lines by 80V. The output of the amplifier is fed into an old switch box and then into the speakers. Eventually, I will design a proper one with proper impedance matching to keep the lines at 100V constantly.

Schematic

PCB Layout

Scale to 41*69mm

2020 OZFix