2. amps-preamps
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Phase Inversion in Preamplifer?

I just bought a used Audible Illusions 2D here on a'gon. This will be my first venture into separates. I've learned that AI preamps have inverted phase, so it's recommended that I switch +/- polarities at the speaker-amp hook-up. OK. But according to AI literature the phono stage of the preamp is NOT inverted, only the output stage is. So, since I listen to both vinyl and CDs, what do I do? Should I reverse speaker wire polarity or not?

Incidentally, the amp I'll be using is an ATI 1502 -- still haven't been able to find out if it inverts polarity or not. But based on my (limited) research thus far it appears that phase inversion is a design of preamplifiers more than power amplifiers. Is that right?

Thanks,
Rich
winegasman

Showing 3 responses by sugarbrie

sugarbrie
3,854 posts
 
The problem with this whole discussion is Polarity and Phase Inversion can either mean the same thing or something completely different, depending on who's talking and what component they are talking about.
sugarbrie
3,854 posts
 
If a system is out of phase you are more likely to hear differences at the frequency extremes, not in the center midrange like vocals. Affects the bass the most in my experience.

I would think having the right channel out the left and vise-versa would ruin the focus/image. Assuming the singer is in the center....
The voice would normally be to the left of the right channel microphones and to the right of the left channel microphone.
Switching the channels puts the sound of the voice on the outside of both channels instead of in the center.
sugarbrie
3,854 posts
 
If your system is phase correct, playing music recorded out of phase will not change the phase of your system. If not a mistake, they may have recorded it out of phase to create the sound they wanted when you play it back, that is all. Grooves on an LP or digital code on a plastic CD cannot invert the electrical signal going through your system or add a gain stage to your preamp. You are playing the sound of something out of phase on a system in phase, that is all.

If your CD player has a polarity switch, not sure if it really corrects it or just makes it something else. I have such a CD player and that owners manual says it reverses polarity, NOT to be confused with inverting the phase.

A way to have fun with phase is to play the same signal through both speakers (use bookshelf speakers). Reverse the speaker wires on only one speaker. Now place the two speakers together face to face. It won't be a perfect seal, but if perfect the sound volume would go away (or in your case it would be greatly reduced). This is because the two speakers are playing the same sound 180 degrees out of phase with each other. They will cancel each other out creating silence.

This is similar to the experiments they do to try to make luxury automobiles quieter. They play the frequencies of road noise out of phase to cancel out the actual road noise, making it quieter inside the automobile.
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