The Symmetra-Peak is a fascinating unit. Completely passive, it provides a phase shift/time delay over the audio spectrum, the magnitude of the effect depending on the frequency. The brochure and patent are interesting. I snarfed these off W3AM's website. Hope he does not mind me calling attention to these units and his work; I got them for myself since I have a couple of these units, but might as well post them. Interested parties will want to check out his site for some very detailed information on audio processing for AM, as well as explanations about what the Symmetra-Peak does and why it is important, why it is a great find, and how this is done today with modern active components.