Phase inverting preamps

Ghostrider is correct about reversing the + and - on the speaker terminals. It is NOT reversing the left and right channels. Some preamp makers (Conrad Johnson, Blue Circle and others) do this because adding another otherwise unnecessary gain stage, just to make the preamp phase correct, would only degrade the sound.

I will add, that a recording that was recorded with the polarity reversed can be corrected by reversing the phase of the speakers, etc. The CD player's (or other source's) output voltage is still phase correct, even if the music was recorded with the polarity wrong. Data on a CD or LP (a piece of plastic) cannot change the actual voltage polarity of the audio component. There are some CD players that let you reverse the polarity of the recorded data at the DAC chip. This does not affect the output voltage polarity of the player itself. A loud bass note in a phase correct system that electrically pushes the woofer out, will do so regardless of how it was recorded at the studio.

There is a BIG typo in my post above. It should say that an out of phase recording CANNOT be corrected by reversing the speaker terminals.

I give up posting on these type of questions. Bob is right, it is simple, if an audio system has an odd number of phase inversions it will be out of phase. Some preamps have a switch to add a stage to change that kind of phase. However, if a CD was manufactured with the polarity reversed, that audio system will still have an odd number of phase inversions in the signal path and is still out phase. You end up with a sound out of phase with the polarity reversed; two different things.

It is sometimes caused by having the microphones out of phase. You will hear the difference, but it does not magically add another electrical circuit to your audio system to change your system's phase. If it does call Moulder and Scully.

In some regard your system will playing an out-of-phase sound, in phase (or an in-phase sound, out-of-phase.)

It is similar to when the AC power socket has that other type of polarity wrong. No matter which way you plug your components in, that same system with the odd number of inversions is still out of phase. Having your AC polarity wrong affects the sound, but not by reversing the phase of your system.

These reversed polarity recordings are similar. It has to be corrected at the CD player when the digital is converted to analog. There are some players that do this.

For some fun reading see:

http://www.mega.nu:8080/gallery/phase_and_polarity.html

Yes, I agree with both of you (Herman and Bowbow). It is just terminology.

Herman: Rent a copy of the movie "The Green Berets" staring John Wayne. There is this one very nice sunset scene on the beach in Vietnam. It is interesting because the Vietnam coast faces east!! Talk about phase inversion!!