Phase reverse box?

[Taylor]

I was reading about a Vermona retroverb, and it says it has an option to reverse the phase of one half of a stereo signal, which creates the psycho-acoustic effect of ths stereo field "spreading out" and becoming more spatial. What would be involved in a box that does just this, and does such a box already exist? I would think that this would actually just make your signal sound bad, like when you wire one of your speakers backwards in a stereo. Any thoughts? I'm not talking about a phaser, by the way. 

[Nasse]

Do a search for such words as retro stereo anderton

You need two amps or some kind of stereo setup (whatever it means ) to play or record it live

[Taylor]

That circuit looks cool, and maybe it's what I need, but it seems to be designed for creating a pseudo-stereo sound from a mono signal. I already have a stereo setup and 2 amps, though. I was just interested in something that make the stereo spread seem wider. Would that sort of circuit do this to an already-stereo setup?

[Satch12879]

A center-tapped transformer will do switchable phase reversing.

[Ge_Whiz]

A bit of simple acoustic-phase theory.

If you feed the same signal in phase to both halves of a stereo system, and listen via headphones or speakers, the sound will appear dead centre in the stereo field (assuming that the levels are identical on both sides). If one of the signals has its phase reversed, the acoustic effect is that the sound now comes from hard right and left of centre. Thus phase difference gives the effect of spread in the stereo field. If the phase is varied with time, or with frequency, or both, various stereo effects become possible.