For future reference, all that PA amp is doing is sending it's output into an impedance matching transformer before sending it to the terminals on the outside of the box.
The actual amplifier inside is the same as a normal PA amp plus this transformer.
Add a transformer to the receiver, and suddenly it too can be a 70V line amplifier. Most cheap receivers these days are MUCH happier with 8 ohm loads (4 ohms may damage them or cause a shutdown), so be sure to get a transformer with an 8 ohm primary.
Stereo mixes are odd, most of the information is on the left channel for some reason. If you have a mono system, connect it to the left output. DO NOT attempt to bridge the output of a receiver, catastrophic damage to the output section may result. This is essentially a short and the protection circuit on most receivers will be blind to this type of fault. Most are only good for same channel lead to lead or lead to chassis ground shorts. Some sort of isolation is required and even then, with anything above line level (1-4V p-p), I wouldn't push your luck.
Radio Shack used to sell a 100W 70V line matching transformer for this purpose, but that was 10 years ago when the still sold replacement speakers during my grade school ultra cheap project days.... I miss the old RS.
Wait I take that back....who am I kidding.... I live 13 miles from the Mouser Electronics warehouse and I have a business account with them so I can do will call.... makes even RS in its heyday look silly and
ridiculously expensive.
