Hi Frogman,
I’ve used Stax Lambda Pro headphones ever since I purchased them in the 1980s. Until 2014 I was driving them with the SRM-1 Mk2 solid state amplifier together with an ED-1. I found that on the majority of recordings it was necessary to switch in the equalization provided by the ED-1, especially to eliminate or mostly compensate for a thinness in the mid-range and lower treble. With that amplifier I would not have wanted to be without the ED-1.
However in 2014 I purchased a used tube-based SRM-T1 amplifier. With that amp and my Lambda Pros the equalization provided by the ED-1 was totally unnecessary, and the resulting sonics were far superior to the SRM-1 Mk2/ED-1 combo regardless of whether the ED-1’s equalization was switched in or out. Frankly I was amazed at the difference; it was as if I had purchased different and much better headphones.
In 2014 I sold the ED-1 for a bit more than $600, and I sold the SRM-1 Mk2 for a bit under $400.
Best regards,
-- Al
Edit: I just noticed that the original post is from 2004! Oh well, perhaps the recent responses will be helpful to someone else.