Question about Stax Lambda Pro Headphones

Q1) Good question. I couldn't find input impedance specs on the 1980s Stax adapters, which would allow a definitive answer. FWIW, though, my guess is that there would be no problem. Not sure I'd bet the health of my amp on it, though. I did find the input impedance of the ca. 1970 Stax SRD-5 described here as follows:

Not more than 30 Ohms anywhere in the audio band. 5 Ohms DC.

If the spec on your adapter is similar, which I would guess it is, there would be no problem. A problem might arise if the input impedance is significantly higher than that, in which case potentially damaging or reliability-degrading "inductive kickback" could occur in the output transformer of the amp (assuming the amp has an output transformer).

Q2) Sure. Stax itself makes several models today, as well as Woo Audio and possibly one or two others. They are not inexpensive, however.

BTW, I also have a pair of Stax Lambda Pro headphones, which I purchased new in the 1980s. I recently acquired a Stax SRM-T1 tube headphone amplifier, ca. 1990, at a small fraction of the price of the current Stax models. It replaced the solid state Stax SRM-1/Mk-2 amplifier and Stax ED-1 Diffuse Field Equalizer combo I had been using for the past 25 years or so. I'm VERY pleased with the improvement. SRM-T1's don't seem to appear for sale very often, but if you see one in good condition grab it!

I've connected these Stax models, btw, to the tape outputs of my preamp, not to the main preamp outputs (which would just introduce unnecessary circuitry and an unnecessary volume control into the signal path).

Regards,
-- Al

Frogman, thanks for the input about using the ST-70 with a Stax Energizer, which of course adds confidence that Mabonn would be ok using his with a tube amp.

Regarding the ED-1, my perceptions have been exactly as you describe. Its most notable effect IME has been to mitigate the tendency of the Lambda Pro/SRM-1Mk-2 combination to sound thin and lacking in harmonic richness, most notably in the upper midrange and lower treble, together with excessive brightness further up in the treble region.

It accomplishes that, however, at the expense of some sacrifice in transparency and definition. How that tradeoff nets out has seemed to me to be recording dependent. And more often than not I had found myself switching the ED-1's equalization off, especially with recordings that are well engineered.

In any event, that mitigation no longer seems necessary now that I'm using the SRM-T1, and so I've removed the ED-1 from my system.

A further point that seems likely to be relevant to Mabonn's situation: Ever since I purchased the Lambda Pro's ca. 1986, and continuing to the present day, I've consistently noticed that if they are not used regularly, and especially if they are not used at all for a period of say a few weeks, they need to be given a good workout to again sound their best. By "good workout" I mean playing them at very high volume (louder than would be safe if they were on your head) for two or three hours or so. Otherwise the negative tendencies I mentioned in the second paragraph of this post tend to become considerably more pronounced.

Best regards,
-- Al

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