Greetings,

I'm looking at a used NAD that has only pre-amp out and no dedicated subwoofer out. Can a pre-amp be used for a sub (EP125)?

NAD:
http://nadelectronics.com/products/hifi-amplifiers/C-320BEE-Stereo-Integrated-Amplifier

If it doesn't shut off the built in amps, I would think that it would work, but I'm not sure how you'd mix the channels.

I'm also looking at this NAD, and it does seem to have a sub out.
http://nadelectronics.com/products/hifi-receivers/C-720BEE-Stereo-Receiver

Have a look at this receiver

Plenty of power, less money and two sub outs.

I have two of them and they are very good receivers for the money.

They go on sale quite often as well, I got two for the price of one on black friday two years ago.

I like the NAD 320 because it is a bit more compact. A radio is not that useful for me as this will go into my basement office. This is for music listening, from my computer. The NAD 720 is a second choice. The HK looks very large.

Sorry, I didn't realize that you were looking for a more compact setup. The H/K is pretty big.

Neil, it'd be possible to arrange the 320 so that the pre-outs could feed a sub amp. The connecting links to the 320 amp would have to be removed and replaced with a Y-adaptor or cable so that both the 320 amp and the sub amp would receive signal voltages. The sub amp would need two line level inputs(the EP125, for example, has one). There really wouldn't be any benefit from going to this trouble, since the 320 would provide no bass management on the full-range signals it sent to the sub amp. A simpler solution would be to connect the speaker level outputs of the 320 in parallel to the speaker level inputs of the sub with speaker wires. The low-pass filter control of the sub would then be used to try to get a good blend with the natural roll-off of the mains.

The 720 has a fixed 100Hz low-pass filter on its combined single sub out. This may or may not blend well with the mains.