rewiring preamp will it work

Al, the DJH does not have coupling caps. It's direct coupled. I don't know how that influences impedance, but I wanted to point it out.

There is very little in the way of documentation on this preamp. I had one for several years and loved it. You should contact Cary if you have any technical questions. They are good about answering.

Thanks, Mingles. That could very conceivably help the situation. The question for Cary then, simply put, is what is the minimum load impedance they recommend for use with the preamp.

Regards,
-- Al

Adding a switch to choose between the two outputs would cure the impedance problems. Of course, anything added to the circuit (wire + switch) may degrade the sound ever so slightly. Probably less compromise than an unpredictable impedance mismatch however.

Your headphones' impedance could be too low even all by itself. Many headphones have impedances like speakers', in the 4 to 16 ohm range. (Putting a high impedance amp in parallel to a pair of headphones would not make a lot of difference.)

Presumably, you would unplug the headphones while listening through your speakers, so the preamp should be OK then. But when listening through the headphones, the low impedance of the headphones could result in damanding more current from your preamp than it can supply without distortion, as others have already aluded.

So, why don't you plug your headphones into the output of your amp instead?