Can you convert a pre-amp to a headphone amp?

Hi Audiogoners,

I have a Rogue Perseus Pre-amp going into a Spectron Musician 3 power amp and Martin Logan SL3 speakers. It sounds great. However, (and here's the rub) the neighbors are less impressed. I would like to do some headphone listening later in the evening. Is there a way to use the pre-amp (or even the power amp) as a headphone amp by connecting some sort of box in there. Ideally it would be something passive so as not to degrade the signal quality (and maybe cost less).

Does such a thing exist, or do I need to get a dedicated headphone amp such as the Musical Fidelity XCan V3?

Thanks in advance,

Here is a Rube Goldberg method. Put splitters on your pre-amp out puts. Plug your amp into one side, and some RCA to headphone adaptor cables into the other. Plug your headphones into the adaptor and listen. If your pre-amp has enuf gain and there is not a gross capacitance mismatch it might work quite well.
On a related note, the Berning MicroZOTL is a superb headphone amp, which can and does double as flea-powered amp for ultra-high efficiency (100+ db) speakers. If matched up right it actually does a very nice job as an amp. I was really impressed. Don't even bother if your speakers are below 100db effifiency, so you're SL3's are out of the running. Highly recommended if you do get a head amp.

Get a pair of Stax Electrostatics and hook them up via their converter box to the back of your power amp. It's just a hassle to connect/disconnect the box. Or really spend the money and buy a dedicated stax amp. you can plug your source directly into the better stax headphone amps as they have a volume control.