Anyone ever use a Dynaco Quadadapter QDP-i

If you don't like the effect you could call it diminished.A

I owned and used one when they were new- maybe 1977 or thereabouts. I recall from the user manual the recommendation that all 4 speakers have similar efficiency and impedance ratings. And- the powering amplifier must have (or use) a common ground between channels. Most do, but it is important to verify!

I really enjoyed my time using the qd-1, especially with certain albums. At the time, I was using Dynaco speakers. I may still have the original owners guide…

This is known as the Hafler circuit, and there are many articles about the circuit, and the man, David Hafler, available to ponder.