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.

Oops!!! Sorry about that! :-)

I was serious about the above though...I had all of my components hooked up correctly, but my left and right chanels were reversed when I played the HFNRR test record. It was all of my sources, so the problem has to be in my Counterpoint SA-5000, NP-100, or Merlin Battery Bamm. I switched my cables to fix the problem. (I assumed that was what people were talking about when they mentioned "phase inverting" preamps, so that explains my posts above)

Has anyone ever experienced a component flip-flopping chanels like that??

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.

There seems to be a lot of confusion about this. There always is. Mr. Ghost is correct.

Phase and polarity are NOT the same thing. A phase shift is a shift in time. A change in polarity is a change from a positive to a negative, or vice versa.

A simple example would be a 20 Hz sine wave that starts at zero volts, goes to a positive peak then decreases until it crosses zero, going negative until it reaches a negative peak and then returns to zero. Like this little symbol ~ .This is one complete cycle of 360 degrees. This happens 20 times a second so each cycle takes .05 seconds.

If this exact same signal had it's polarity inverted, it would start off going negative instead of positive, but would start at the same time.

If this exact same signal was phase shifted 180 degrees, it would start off going the same direction, but it would do so 1/2 cycle (.025 seconds) later or earlier in time.

Thus the comment about "flip the signal 180 degrees back to positive polarity" is wrong. If you are dealing with a repetitive waveform like a pure 20 Hz sine wave, than a phase shift of 180 degrees will look just like a polarity inversion. Draw a picture and check it out. But music is not so simple.

The comment from Mr. Brie is also a little off base. The recording is not out of phase, it has had it's polarity reversed. When you engage the phase button (should be polarity button)) you do indeed invert the signal. What was going positive will now be going negative, and vice versa. This can also be done by reversing the speaker leads. The common example is that of a drum that produces a very short WHAP sound. Lets say the initiation of the original WHAP sound caused a compression of air. The initial movement of the speaker cone should be towards the listener, which will also compress the air. If the polarity is reversed anywhere along the path form micrphone to speaker, the initial movement of the cone will be away from the listener causing the opposite. Whether this is audible is another story.

Of course, Herman. It was an attempt to account for the confusion w/re phase and polarity. But it doesnt matter in this context. All the preamp owner needs to know is to reverse his speaker cables, and not left to right as he was told. He doesnt need these 1000 word essays.