Question about Stax Lambda Pro Headphones


I have an old pair of these headphones, 1980s vintage. They are driven by an "ear speaker adaptor" which connects to the speaker terminals of a power amplifier. Question #1: Is it safe to use these with a tube amplifier ? In other words, when the selector is switched to phones, does it present a safe load for the amplifier ?
Question #2: Is there a tube headphone amplifier available that will drive these headphones ? Preferably one that can be driven from pre-amp outputs ?
mabonn
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 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.