Hi Wid,
FYI, even if an older stereo receiver does not have "amp-in" connections, you can use any analog line input except "Phono" as an "amp-in" connection.
Line-level inputs and pre-amp outs are standardized to accept, or output, respectively, at 1 or 2 volts. Pre-outs of course will output more depending on the setting of the other receiver's volume control.
The reason you can't use a Phono input is because it contains not only an extra gain stage for the tiny 5-millivolt output of a moving-magnet cartridge, but an RIAA equalization circuit (or two extra gain stages for a moving-coil cartridge, whose output is in microvolts).
Cheers,
Alan
