In or out

[Edgy_Gecko]

I am an absolute newbie and I want to learn more about guitar electronics. Although I have been constantly researching and gathering schematics I need to know one thing that keeps poping up. What does in phase and out of phase mean? Can Some one give me an acurate description?

[ansil]

of course but it involves basic math so here goes.

a sine wave is roughly what our instruments puts out..[this is for learning purposes.] there is a positive peak and a negative peak the positive peak is positive phase and the negative peak is negative phase.

if you apply basic math skills to this problem you will see how to apply guitar soundwaves in the same equation.

Johnny has Five apples

Johnny owes five apples to Ansil.

how many apples does Johnny have.

Answer -2 because i am charging interest..

JUst kidding.

when you take equall phased positive and negative signals they will cancel each other out resulting in a weak sound.

now you can also talk about magnetic phase but essentially the results are the same.

[Dugz Ink]

I always explain it like this:

Sound waves travel in a "wave" shape, starting with a positive value that is displayed as a peak in the wave shape, and ending with a negative value that is displayed as a trough in the wave shape. This is also known as being "in phase."

As the distance to the source of the audio becomes greater, a microphone becomes "out of phase" from the instrument due to the time it takes the sound to reach the mic; in a manner of speaking, the mic could be picking up the sound wave half way through the peak while the sound that is eminating from the instrument is just reaching the trough.

If your mic is at a specific distance in specific atmospheric conditions when you play a specific note (frequency) then the microphone is 180° "out of phase"... a state we also call "phase inverted"... because the mic is picking up the sound wave when it is at the highest point of the peak while the sound that is eminating from the instrument is at the lowest point of the trough.

In the case of phase inversion, the positive value at the instrument is identical to the negative value at the mic. In mathematical terms, the instrument's value is +3 while the mic's value is -3. Add the two together (+3 + -3) and you get a value of ZERO. This is why mixing an "in phase" signal with an "inverted phase" signal will yield "no sound".

When it comes to wiring your gear, connecting the "positive" to the "positive" will provide an "in phase" signal. But connecting the "positive to the "negative" creates an "inverted phase" because you are sending positive values down the negative connection. When this sound is played back over speakers, it sounds strange because the positive/negative values are now switched, so the speakers are "pulling" when they should "pushing" and vice versa.

That's basically a layman's description, and glosses over some of the technical details, but I hope it helps. If not, then your next question is FREE.

D~s

[Saber]

Here's another way to explain it. I'll use the analogy of stereo speakers to begin with. When the 2 speakers of a stereo system are correctly connected "in phase", and a mono signal is played through them, the speaker cones will move forward and backward at the same time so that the sound of the two will be added, and the result will be twice as loud as if only one was playing.

If you reverse the polarity of one of the speakers, then whenever one cone is moving forward the other will be moving backward so the sound of one speaker will be subtracted from the other. Theoretically, the result would be no sound, but in the practical world you just hear a very weak sound.

Again with one speaker connected out of phase, if the program material uses a lot of stereo imaging, then the sounds that are identical in both speakers (usually the bass sounds) will cancel each other out and be almost inaudible, and sounds panned to one side will be more easily heard because there's no out-of-phase equivalent from the other speaker to cancel it out.

With guitar pickups, the same thing occurs but electrically. When 2 pickups are connected in-phase, the sound of the two will be added together. When you reverse the wires (or polarity) of one of the pickups, the frequencies or harmonics that are common to the 2 pickups (especially the fundamental frequency) will tend to cancel each other. And whatever's different between the 2 pickup signals will be audible. Overall, it's a weaker signal but with its own unique sound.

Edited September 18, 2004 by Saber