lhulls,

No, the preamp section typically does not have enough gain to drive headphones. If you want to test that thesis, try connecting a pair of headphones to the main channel left and right pre-outs of an AV receiver. In most cases, you'll hear only a very weak signal. That is why the amplifier output is used, much attenuated.

Regards,

Alan Lofft,
Axiom Resident Expert (Retired)