View Full Version : Preamp polarity questions....

09-09-2005, 05:39 PM
Hey all. I did a search and learned some, but I still have questions.

I have the following:

-ProTools 002R, running on an Apple PB G4
-R0DE NT1-A into a Presonus Eureka Preamp (Comp & EQ bypassed) with digital out
-MXL V69 ME with NOS Mullard tube into a Rane MS1b, into Eureka's 2nd digital out
-Both digital channels go into the 002R via high-quality S/PDIF

Now then, I am NOT looking for opinions on the gear, as valuable as yours may be. I am wanting to know about the polarity switch on the Rane.

I just hooked up this signal chain to record acoustic guitar. I love it. The R0DE condenser is the main mic, placed at the neck/body joint, and it sounds bright and clear. The MXL is the ambient mic, placed two feet back and directed toward the lower body of the guitar to pick up lower frequencies. It sounds nice, too.

I played a song and recorded each mic to a mono track in PT. Listening back, they each sounded great separately. However, when I played them simultaneously, the Rane track sounded horribly strident. So, I flipped the "Polarity" switch on the back from "Normal" to "Invert." The difference was night-and-day better. Panning the tracks left and right made it sound like I was playing a Jumbo on one mic and a Nashville on the other.

My question is this: What does this mean from here on out? Is it normal to have to flip polarity on one mic when using two? Does it have an effect on the recorded track that needs particular handling? Does polarity even matter if the tracks are panned to opposite sides? Is this a function of the difference in physical distance of each mic to the guitar (length of the sound waves)?

Any answers on this topic would be greatly appreciated.



PS - Notice that I have disabled the Comp/EQ on the preamp. I am trying to record as clean a signal as possible so that I retain production options later. Keep this in mind when answering my questions.

09-09-2005, 07:55 PM
This article (http://www.songstuff.com/articles.php?selected=50) might shed some light on it.

09-09-2005, 08:17 PM
Good article! Thanks for that.

I'm still open to other input, but that settles my mind on a few points.

Thanks, Spk.


09-10-2005, 04:25 PM
Other input...not all manufacturers are consistent (or care) about polarity. My simplest advice: if it sounds right, it IS right. Going deeper, you might find the same result by switching polarity on the other preamp (it is MOSTLY an issue of comparision or combining of signals). There are people that claim to be able to hear the difference on a single input (and some actually can) and you may find you notice one polarity sounds better than the other(especially depending on the frequency range of the signal). Those polarity checkers are a valuable tool. The average home studio could have mic cables wired wrong (even from the factory) or DI boxes wired wrong (yes Countryman, I mean you). Just imagine what can go wrong in an 80 box, 120K watt PA system! Keep learning and listening and you will get it.

09-11-2005, 10:26 PM
That sounds like great advice. Thanks for everyone's help!

09-12-2005, 12:49 AM
if someone thinks they can hear the difference on a single mono channel by playing with the polarity switch, it probably means something in their system is broken.

having said that, yes - phase across multiple channels is tremendously important (and probably the single greatest problem with effectively mic'ing up drum kits).

also, remember the distance a sound source is from a microphone will affect the effective phase of some types of signal. sometimes you can correct this by going into pixel-level edits and dragging a channel back so the peaks match up perfectly.