The best way I've found to run a pair of Lambdas is to use the Class A headphone preamp Stax made for them in the 1980s. It was called the SRA-12S. I had one, and used it for my regular preamp, and the Lambdas. It had output jacks for 2 sets of Stax phones. No attaching to the amp's speaker leads was required, it was all done in the preamp. Let me tell you, this thing got hot! You could fry an egg on top of it. There were inputs for 3 types of phono inputs, MC,MM,and Stax proprietary strain gage cartridge. There was a tape loop, aux, and at least 1 pair of main outs. All volume, balance, and switching was done on the front and the 2 jacks for ES phones were on the front. I ran this as the main preamp with a Stax DA-80 amp for awhile, and it sounded pretty good. Between the 2 space heaters, it was too hot for me to keep. I just knew that all that heat was no good for the passive components in those units. But the ability to properly drive the Stax phones was unsurpassed. It was built like a tank, with all the quality you'd expect from the old Stax line.