OOPS wired amplifiers

RobHolt

RobHolt

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Stay with me......

Way back in the mists, must have been early 1980s I recall a magazine article in Hi-Fi Answers on something known as OOPS (out of phase system) for improving amplifier performance.

The idea was touted as a free way to squeeze a little extra from stereo amplifiers sharing a common power supply.
You invert the phase of the source on one channel only and then restore it by reversing the speaker connections on the same channel. So you have the signals out of phase as they pass through the amplifier. Why?
Well, the idea is that when both channels are playing in phase they will be making equal demands on the PSU rails at precisely the same time, both swing to positive and negative together. Reverse one channel and you give the PSU an easier time, so the theory went.

Anyone remember this or tried it?

The recollection is a bit foggy and I might have got it wrong, so please correct things if you recall the idea.
 
RobHolt said:
Stay with me......

Way back in the mists, must have been early 1980s I recall a magazine article in Hi-Fi Answers on something known as OOPS (out of phase system) for improving amplifier performance.

The idea was touted as a free way to squeeze a little extra from stereo amplifiers sharing a common power supply.
You invert the phase of the source on one channel only and then restore it by reversing the speaker connections on the same channel. So you have the signals out of phase as they pass through the amplifier. Why?
Well, the idea is that when both channels are playing in phase they will be making equal demands on the PSU rails at precisely the same time, both swing to positive and negative together. Reverse one channel and you give the PSU an easier time, so the theory went.

Anyone remember this or tried it?

The recollection is a bit foggy and I might have got it wrong, so please correct things if you recall the idea.
Click to expand...
Yes tried it, it was a bunch of cock unless you were really providing a cheap PSU, you might get a benefit from a walmart type plug in. Anyway using discrete channel PSUs is a much better solution.
 
How do you invert the phase of one channel in a stereo amp with unbalanced inputs? Both channels have a common earth.

Was extra circuitry needed, or was it possible with phono cartridges and rewired tone arms?
 
It was usually done by reversing the blue and white phono cartridge connections.
 
RobHolt said:
It was usually done by reversing the blue and white phono cartridge connections.
Click to expand...

I remember doing this now, after reading the article in HiFi Answers. Reversed the blue & white on my Ortofon VMS 20 (on a Dual 505), sat back and listened to it through a NAD 3030 and Mission 710s, and wondered whether or not I was deaf, cos I couldn't make out any difference.

Stupidly left set-up in place when recording some vinyl on a good old JVC cassette deck. Sounded fine played back through my system, sounded crap (OOP) on other systems, leading to curious looks in my direction for the crap party tape...
 

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