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Microphone Month

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Balanced, Unbalanced, Stereo? what are they?

sabianq

In the professional audio world,
we work with a type of signal called a "balanced" signal. you might be familiar with the XLR connection:

but less known is the TRS, paradoxically widely known as a 1/4 inch stereo plug.
this stereo plug is only a stereo plug when it carries two channels of unbalanced audio. otherwise when it is used as a single channel connector in a balanced system, it is called a balanced TRS connector or 1/4 inch balanced TRS

a common misconception is that fact that when used as a balanced connector to connect a mixer to another piece of pro-audio equipment, this plug is not a stereo plug, it is a single channel plug that is balanced.
So what is a balanced signal?
i will refer to my post in an earlier section so i don't have to retype all of this:
http://www.audioforums.com/forums/showthread.php?t=13988&page=2&highlight=balanced
the balanced cable method is a way of minimizing unwanted noise from audio signals along very long runs of cable.
the principle of Balanced audio is that two identical signals are inverted 180° out of phase will cancel each other out. balanced cables in such systems are designed to carry two versions of any given signal and are manipulated in polarity relative to each other to eliminate noise and hum.
Balanced single channel cable

this will make more sense when we examine unbalanced and balanced cables.
unbalanced cables not unlike balanced cables use two lines to transmit the audio signal but part of the audio signal is carried through the ground.
un-balanced single (mono) channel cable

unbalanced stereo (line level) cable with rca and 1/8 inch stereo plugs

a hum can be picked up in these cables if the run is to long or if there is a difference in voltage potential on the ground of the the chassis of your equipment (this can be caused by plugging your equipment into two different power sources with a voltage draw between your common and ground)
There is a common misconception that Balanced audio equipment and cables are quieter than unbalanced equipment.
quite the contrary, as balanced equipment is great at hum rejection and is used for live "pro" applications, some of the best equipment in the world designed for mastering and audio reproduction is actually unbalanced.
The actual electronics in your Balanced equipment is actually unbalanced is just isolated from the chassis. the ground shielding of the cable provides a route for radio frequency and induction hum to get to ground without infiltrating the entire signal, any hum or RF frequency is canceled out when it propagates down the cable when it hits the other end leaving the audio signal by itself.

as you can see, there are great advantages to using balanced equipment.
for one, your pre-amps for recording are extremely sensitive to interference, induction hum and radio frequency (RF) infiltration, the use of balanced cabling eliminated that potential for radio and noise interference.
lets look at exactly how unbalanced cables work
paraphrased from this website
http://www.mediacollege.com/audio/balanced/cable-balanced.html
Balanced audio cables use three lines, they consist of a hot line (positive), cold line (negative) and earth. The audio signal is transmitted on both the hot and cold lines, but the voltage in the cold line is inverted in polarity so it is negative when the hot signal is positive. These two signals are often referred to as being 180 degrees out of phase with each other but this is not exactly correct as the signals are not delayed to be out of phase but are inverted so they are not in polarity.

When the cable is plugged into an input (on a mixer or other equipment) the hot and cold signals are combined. the signals are combined and placed back in to correct polarity and the signal becomes stronger. that is why you can run a balanced cable fro thousands of feet without signal loss.
the connectors of a balanced cable have no effect on signal quality.
there are many different types of connectors because different manufactures have different ways.
the most common are the TRS and the XLR
the TRS or commonly misidentified as the 1/4 inch stereo phono plug means (Tip Ring Sleeve) the Tip (3) and Ring (2) Carry the signal and the Sleeve (1) is the ground.

the Mono plug or 1/4 TS connector is used in many different applications, but normally carry a signal along the ground (sleeve) (1) and the Tip (3).
The mono plug can be used to carry Speaker level signals in older PA gear but more commonly is used to carry instrument level signals like from an electric guitar to the direct box.
history of the XLR taken from
http://www.soundfirst.com/xlr.html
At one time Cannon (now ITT Cannon) made a large circular connector series that was popular for microphones called the P series. Mics used the 3 pin P3 version. Some loudspeakers use the P4 or P8 versions of this connector to this day.
In an attempt to make a smaller connector for the microphone market Cannon came out with the UA series. These were "D" shaped instead of circular and were used on such mics as the Electro-Voice 666, 666R, and 655C.
There was a desire for a smaller yet connector. Someone pointed out the small circular Cannon X series. The problem with this was it had no latch. Cannon rearranged the pins and added a latch, and the XL (X series with Latch) was born. This is the connector others such as Switchcraft and later Neutrik have copied.
Later Cannon modified the female end only to put the contacts in a Resilient Rubber compound. They called this new version the XLR series. No other company has copied this feature. It is amusing that XLR has become the generic term since what everyone else copied was the XL and not the XLR!


so you can see that the connector is just a fancy way to connect equipment.
there is no difference in the audio quality of different balanced connectors.
August 30, 2007 @05:50pm
still

I have two separate line level 1/4" unbalanced outputs. I have one line level stereo 1/8" input. Is it safe to send both unbalanced outputs via "Y" cable into the stereo input? If so, then will one signal go to left and the other to right?
My concern is that the two line level signals will overload the input, but I hope I'm wrong.
Thanks.
August 1, 2009 @12:30am
still

Thanks for the reply!
August 4, 2009 @11:05pm
regutz

Safe, but inadvisable if optimal performance is desired, as each output ends up driving a load impedance that is as low as 50 Ohms. The outputs need to be resistively summed. See Rane Note 109: http://www.rane.com/note109.html

Yes, this dual mono to stereo Y-connector is safe to use.
The 'Rane Note 109' talks about a stereo-to-mono Y-connector.
Cheers!
December 14, 2011 @07:24am
bouldersoundguy

I have two separate line level 1/4" unbalanced outputs. I have one line level stereo 1/8" input. Is it safe to send both unbalanced outputs via "Y" cable into the stereo input? If so, then will one signal go to left and the other to right?
My concern is that the two line level signals will overload the input, but I hope I'm wrong.
Thanks.

Regarding the title of your post (Dual unbalanced to single balanced. Safe?), you aren't going to a balanced connection but a stereo one on a single plug. If you actually connect a stereo signal to a balanced input like that you would decode a difference signal. This is why in the pro world we are fairly particular about how we reference connectors. "Stereo" and "balanced" are applications while TRS and XLR are connectors. TRS connectors can also be used for inserts (send/return/ground) or for amp channel and effects switching. XLR is also used in lighting control systems, very occasionally for stereo and even on speakers.
December 17, 2011 @04:55am
carefree

Currently, i am using unbalance rca to xlr individual cables and a 10m xlr cable extention (from the unit rca line output to the speakers).*
It works like a charm from the karaoke player, however I want to utilise my existing mixer/amplifer and using the same wiring only 1 channel works (i am able to switch speakers/wires with this working output channel but the other output is dead signal).
I was advised by the retailer that if i connect 1 speaker it will be mono and 2 speakers from the get go will produce stereo (this was originally for the speaker wires not rca line out). I am uncertain if this has anything to do with my problem, or either the amp is broken, or my wiring (done some googling on unbalanced, balanced, mono, stereo and also on some unbalance/balance converter unit).
Thanks
February 12, 2012 @01:23pm
bouldersoundguy

"Speakers." "Mixer/amp." "Karaoke player."
Gonna need more info than that.
February 12, 2012 @04:27pm
carefree

I had just purchased x2 mackies srm450v2 (they use xlr cables)
My amplifer & karaoke/cd player are foreign hence why I attempted to describe them as best as possible. But here goes another try:
Karaoke/cd player model - Arirang AR-3600s
This player output is similar to a dvd/blu-ray player with 5.1 output at the back (1 rca for each channel i.e FL, FR, SR, SL, sub and video)
There is no problems with this player or either of my other players as I had isolated this by connecting other amplifiers and even the mackies using unbalanced rca to xlr cables.
Ampliifer/karaoke mixer model - Arirang SPA 909A
On the speaker terminal it does say use minimum 200watt @ 4ohm, i initally wired in some old karaoke speakers at 4ohm and blew them (the speakers stunk, and i do not know if this is causing the problem).
Please note - the retailer overseas also advised me to wire two speakers to produce stereo, else it will be mono (again dont know if this is causing issues)
Now, i am using the amplifers line out using the unbalanced rca to xlr cables for each channel. Only left channel is producing a signal to the amplifer by utilising the player or mic connected. The other channel no sound, please note as its a karaoke amplifer there isnt usually a distinctive left and right. The sound produced in left sounds mono.
Should i use a 2 rca (left and right) unbalance to xlr balance di converter unit thing?
Or any ideas?
February 13, 2012 @12:20am
Drew_Free

So I'm trying to record workout videos using a wireless headset mic (Samson CR77) but the audio that is getting recorded along with my video is coming out mono. The UHF receiver has balanced and unbalanced outputs. I'm using the unbalanced output (1/4") and then having to use an adapter to get it to 3.5mm so it can plug into my little Canon HD video camera. How can I get this signal coming into my camera to record in stereo? Do I need to use the balanced output with an adapter to get it to the 3.5mm input on my camera? Or do I need to get some different kind of adaptor?
June 5, 2012 @06:38pm
AndyH

Almost all microphones are mono, except for the not the terribly common stereo microphone, which is two normal microphones built into one package. Each microphone input is properly recorded to one track (mono). Stereo requires (at least) two independent inputs. These two (or more) could be recorded to the two channels of a stereo track but in almost all cases it is more useful to record individual mono tracks and process them as desired, post recording.
If you mean that the recorded audio track is playing back through only one channel of a stereo playback system, there are two possibilities.
(1) you have (improperly) recorded a stereo track. Since the microphone input is mono, it only goes to one of the two tracks, leaving the other blank. Record to a mono track and you will get equal output from both playback speakers in most systems.
(2) you have (properly) recorded a mono track but the connection to the playback system is sending this mono track to only one side, instead of (the normal for this situation) both channels. You need a Y adapter or a mixer, or some more useful interconnect. This depends upon your system.
If you have adequate software, after recording you could duplicate the mono track into both channels of a stereo track to get it to play through both sides of your stereo playback system.
June 5, 2012 @07:57pm
Drew_Free

Thanks for you reply AndyH. I'm trying to figure out an easy fix for my problem. I'm using iMovie to edit my workout videos. The fix within iMovie does exist but is tedious and will double the time it takes to edit my videos.
The wireless microphone's receiver has a 1/4" unbalanced output which I've put an adapter on (1/4" female to 3.5mm male) so that it'll plug into my video camera. Is there anything other type of adapter that I can add to this set up so that my video camera receives a stereo input coming to it? You mention using a "Y" adapter but there's only a single input into the video camera. You also mention using a mixer. What type of mixer should I get?
Do you know of a simple solution to my problem? Does everyone that records video using a mic face this problem?
June 6, 2012 @07:07am
AndyH

It really isn't a problem. One mono track per microphone is the norm the world over. This is the most versatile and generally most useful way to record. However, if your camera has two input channels, so that it is capable of recording stereo, but you want to use only one microphone, it is possible to record that one microphone to both channels at the same time. This will produce two identical audio channels; there will be nothing stereo about it.
If there is one input jack on the camera for a stereo input, then that jack is like the output jack on any personal audio player. Look at any headphone that plugs into a personal player and gives the wearer the two channels of stereo, one to each ear. You will see that the plug on the headphones has three section: the sleeve, the ring, and the tip. These sections are for three separate electrical paths: the right channel, the left channel, and the common ground.
Your unbalanced microphone's plug will have only two sections: the signal (neither right or left, just the one and only signal) and the ground. If there is a real balanced output, it is still only one channel of signal that expects to play into a balanced input for noise cancelling functionality.
Adapters going one input to two outputs are commonly available. You need one that accepts a male mono (two sections) and internally connects its signal to both the right and left outputs. The output of that adapter will have three sections, as described above. I imagine the 1/4 to 1/8 inch adapter you are using has only two sections on its output to the video camera. The other possibility is that it is a stereo to stereo size change adapter and it expects two input channels (the three section plug), which your microphone does not have.
While I said that this one input to two outputs adapter is common, I'm not sure about the general availability of the size change (1/4 to 1/8) in a single plug with the channel merge. I know balanced to unbalanced cables in 1/4 phono are widely used but I've never had a need to reduce this to 1/8 inch. It may require a two step connection, one for the size, one for the channels, or perhaps both together in one adapter may be as common as three leaf clovers.
You must realize that all this is relevant only if the camera has stereo input. You haven't really described your current results. If the recording process produces a stereo track with the signal in only one channel, then stereo input capability for the camera seems likely, but if your unsatisfactory result is something different, then since I don't know what it is, it seems pointless for me to make guesses.
I see that your first post says the microphone receiver has both balanced and unbalanced outputs. If this is truly what they are, that is unlikely to be helpful in your particular circumstance. However, if the device is actually set up to just provide two identical channels on the "balanced" output, then all you need is a stereo 1/4 to 1/8 adapter: two channels in, two channels out. The receiver is providing the splitting of the one microphone signal to two outputs. -- again, the usefulness of this depends on the camera's input capabilities.
June 6, 2012 @10:22am