Question about Stax Lambda Pro Headphones

I am sure that Al can do a much better job of explaining this, but my understanding is that it is not simply an issue of connectivity (cable/plug) compatibility. The Stax tube headphone amps are designed specifically to power their headphones; I don't think that, for electrical reasons, any other tube headphone amp would work. I have seen and read about one or two one-of-a-kind tube amps made by hobbyists for use with Stax cans, but am not aware of any made commercially other than the Stax amps. Additionally, I would not assume that a good tube headphone amp (even the Stax; as good as it is) is a sonic improvement over the SRD7 with a good tube power amp like your AR. IMO, if you are primarily a headphones listener and if you can live with the somewhat subtle sonic degradation to the sound from your main speakers as a result of using the SRD7 (I couldn't), then it seems to me you already have the best, or very close to the best, possible sound from your Stax cans.

Yes, as far as I know the only headphone amps suitable for use with the Stax "Pro" phones, which would provide the right bias voltage (580 volts), the right signal characteristics, etc., are those specifically designed for them. As I mentioned, though, Woo Audio and one or two others manufacture such amps, as well as Stax.

Here are links to the currently produced Stax models.

Links to the Woo models are near the bottom of this page.

Here are links to a couple of others.

I have no first hand knowledge of how using the SRD7 vs. one of these amps may compare sonically. I can say, however, that I doubt that anyone's sonic perceptions can be counted on to be more reliable than Frogman's.

Also, member Larryi, whose perceptions are also top notch, provided comments about some of these amps here.

Regards,
-- Al

Thanks for your replies. It has been very helpful. I think I will stand pat !

Thanks for those links, Al. Man, I had no idea. I have to admit that those amps look very interesting. For now, I am content with my Stax amp; but.....

Back in the 1980s, shortly after the Lambda Pro came out, I listened to both and thought the Pro sounded too bright (at least to my considerably-younger self), so I picked a pair of the considerably-cheaper regular Lambda. I have not heard any other Stax phones since then. 

I still have them and am still happy with them, and have used them all these years via the SRD-7/mk2 hooked up to a variety of power amps. Back in the day, I listened to headphones a lot more than I do now.

Now it’s an occasional thing. With all headphones I get a tiny soundstage right behind my forehead, but other than that, I have always been happy with them.

This is probably an extinct product, but I have a 25-foot Stax extension cable. The Pro has a five-pin plug, the regular Lambda has a six pin plug. This cable has a six-pin female end, so you can attach it to any pair of regular or Pro Lambda earspeakers, and a spring-loaded 6th pin on the male end that will retract if you plug into a five pin socket. 

The danger is is that the retracting pin will let you plug your non-pro phones into a pro-voltage socket when using this cable. 

The SRD-7/mk2 has one of each socket on the front. I put a sticker over the five pin socket just to be sure nobody ever plugged my phones into the wrong one and fried them.