Keep in mind that the receiver may have line-level outputs which are not specifically labeled as such. See if it has TAPE OUT or TAPE RECORD jacks.
I've never seen a receiever that didn't have a TAPE OUT or TAPE REC. jack.
Of course, if it doesn't you could always get a line output converter (as used for car stereo amplifier installations) and connect that to the speaker level outputs to get a line level output.
