Receiver is a pristine Denon DRA 750. Sub is a Klipsch RW-10D with low level stereo input capability.
You can certainly hook up the tape record output to your powered sub - I haven't seen one yet that didn't have a low-pass filter built in. So the frequency range is not the problem. Really the problem you are going to have is that the output on the tape record output is not attenuated by the volume control. So basically you are going to get the same volume form your powered sub when the volume is down very low as you will when you crank it up. So you'll have to use the volume control on the sub quite a lot.
Double-check to see if your subwoofer has speaker-level inputs. That would be a better way of hooking it up, if you can.
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