Earphones driven by preamp RCAs?

I am also interested in finding out more on the topic....lately I find myself browsing through the for-sale ads for headphones, but my current setup (pre, cdp or amp) does not have a headphone jack. It would be great if I could avoid buying a separate HD amp. I'll be keeping an eye on this thread...

It may maximise the power transfer but if there isn't enought drive power to begin with it won't matter.

Antique Sound Labs (ASL) makes an impedence matching device specifically for driving headphones from a high voltage pre-amp RCA output. If anyone wants more info, email me off-forum.

I have plenty of volume at 12:00 - that is not the really what I am interested in here.

What about the quality of the sound? What if I compare my headphones on the pre, to my headphones on a headphone amp RCA, to my headphones on a pre with a headphone jack? Sure, the answer will depend on the specific units compared, but how do they compare in general? What are the pros and cons? If I wanted to get the best sound, which direction would I go? Or are all three just as capable?

If I already own a fantastic pre (RCA out only), would there by any reason to add a headphone amp?

Thanks

1. In general, a well constructed purpose-designed device, like a headphone amp, will be superior, for driving headphones. Note, they have a much lower input impedance than that of the average amp. Of course, such a general statement is irrelevant when you get to real-world specifics.

2. Just because it's loud enough does not mean that it has enough power to work into that load without distortion. A 12 o'clock setting is pretty high (in general and without knowledge of your preamp or the gain curve of the pot). Is that where you set it to feed the amp/speakers?

3. Why not just try a decent headphone amp and see for yourself if it is better? Surely, there are web dealers with a useful return policy.