balanced vs unbalanced inputs, etc

J

j

New member
my pc audio interface (aardvark direct pro 24/96) sports balanced inputs..i'm not sure exactly what those are, cept that they are more often found on 'pro' quality equipment than on cheap crap.......i use a line6 pod and run it into the sound card with cheap trs cables which must be unbalanced...however, the pod also has balanced outputs.....do you have to use balanced cables? i'm thinking that you must ...that is if you want to take advantage of the balanced ins and outs.....also, is it really that big a deal anyway...any really good reasons for taking advantage of the balanced ins and outs?.....if you are in favor of using balanced cables in this type of situation, could you suggest a good place to purchase them mail order..i just flipped thru the musician's friends catalogue and didn't see any balanced cables (though i may have over looked them)...thanks,
j
 
Man, I'd kill for the BBS search engine to be up and running right now... There's many great discussions in the archives on this exact topic, with links to websites that have diagrams and everything. Since that's not the case, you'll have to settle for my version of the answers to your questions. BTW, you are just hitting the tip of the iceberg of cable discussions. You'll find lots of good posts recently that compare different brands of cable. In other words, balanced or unbalanced isn't your only cable decision. Higher quality cable like the Monster Pro stuff is expensive, but some people say the difference is worth the money. Anyway, that's just FYI... Now onto the question you asked...

You never HAVE to use balanced cables with balanced input and output connections just to make it work, but the connection will be unbalanced if the cables are and it can make a difference in the amount of outside interference and hum you might pick up. If you are using short cable runs then it's no big deal. If you are using cables that are like 20' long or more and running them next to all kinds of electrical lines and equipment, then having balanced connections will cut down on the noise level considerably. TRS stands for Tip Ring Sleave, and means the cable is balanced. Most normal instrument cables (guitar) aren't TRS though, so make sure you have TRS cables and aren't just refering to an unbalanced instrument cable as TRS. (This is where that diagram would come into play nicely :cool: )

You should be able to buy balanced cables from Musician's Friend, search their website if you don't see them in the catalog.

Here's a sample of the HR FAQ on the main HomeRecording.com page that gives some more details on balanced/unbalanced connections.
-----------
Balanced vs. unbalanced is a different matter: -10 is usually unbalanced, +4
is usually balanced. Balanced lines offer excellent immunity from hum and
noise pickup. This is usually the reason a studio is using +4dB because
they want the balanced lines.
An unbalanced line has the "hot" and "ground" wires.
A balanced line contains a "positive" and "negative" (electrically
inverted) copy of the signal (called "hot" and "cold" respectively), plus a
shield ground. The receiving-end of the cable inverts the cold and adds it
to the hot (assume the "value" of the signal is 1:

N = noise pickup in the cable
hot wire + (- cold wire) = 2
(+1 + N) + (- (-1 + N)) = 2

You end up with a double-voltage signal (the doubling is 6dB of gain). Any
noise pick up cancels out neatly.

These are line levels. Mic levels are typically about -50dB, instrument
levels are about -20dB (but they can vary widely).
-----------

[This message has been edited by Jon X (edited 05-20-2000).]
 
first, thanks for the info.....did do a search for 'balanced cables'before i posted my message , but the first few hits didn't really say much about balanced vs unbalanced...i did, however come across a discussion of monster cables...they sound very expensive.

guess, i'll do another search later...i am still curious about the difference between operating at -10 , or +4....thanks, j
 
There is no noticeable difference in audio quailty between +4 and -10 if used properly and short cable runs, even if +4 is the standerd with Pros.

If you are using cheap cables then that should be a consideration.
 
Here's a link to another site that gives easy to read and understand info about Balanced vs. Unbalanced Connections. http://homerecording.about.com/entertainment/homerecording/library/weekly/aa082697.htm?rnk=r&terms=balanced

Here is a link to very detailed and technical information about the subject, including the different Decibel units/terms (i.e. dBu, dBV, dBv, etc.) Warning this one will make your head spin for a while, but if you REally want to know this site has everything that you want and don't want to know about dB's, balanced, unbalanced... on and on.
http://www.prorec.com/prorec/articles.nsf/files/EA68A9018C905AFB8625675400514576

Rev E
 
ø Balanced vs. unbalanced is a different matter: -10 is usually unbalanced, +4
is usually balanced. Balanced lines offer excellent immunity from hum and
noise pickup. This is usually the reason a studio is using +4dB because
they want the balanced lines.
An unbalanced line has the "hot" and "ground" wires.
A balanced line contains a "positive" and "negative" (electrically
inverted) copy of the signal (called "hot" and "cold" respectively), plus a
shield ground. The receiving-end of the cable inverts the cold and adds it
to the hot (assume the "value" of the signal is 1:
N = noise pickup in the cable hot wire + (- cold wire) = 2
(+1 + N) + (- (-1 + N)) = 2
You end up with a double-voltage signal (the doubling is 6dB of gain). Any
noise pick up cancels out neatly.
These are line levels. Mic levels are typically about -50dB, instrument
levels are about -20dB (but they can vary widely).
The difference between dBu, dBV, dBv, and a dBm?
dBuV and dBmV imply a reference level of one microvolt and one millivolt,
respectively - which are simply not relevant here.
dBu is referenced to 0.775 volts (1 mw into 600 ohms)
dBV is referenced to 1.000 volts (1 mw into 1000 ohms)
dBv is the same as dBu (0.775 volts... just to confuse us)
dBm is the old power reference of 1 mw
Note also that dBm is 10log(P/Pref) while dBu,V,v is 20log(L/Lref).
Pro gear indeed has a larger signal - by a large margin (though not 14 dB!)
A X-Y mic'ing setup?
The following was taken from a mailing list posting
I keep reading about this particular mic technique suited for acoustic
guitar. Its called the X-Y setup, or something like that. I know it
involves 2 mic's with different placements, but I am not clear on how
these are to be set up. If anyone could shed some light on this, it
would be appreciated.
Sure, it's real simple. It takes two directional mic's and you want them to
be as closely matched as possible. By directional, I mean either cardioid
or hypercardioid, pickup patterns. Omni won't work for this technique,
since it depends on the directional response of the mic to get a stereoeffect.
You put the mic's with their capsules as close together as you can get them,
and have them pointing at angles to each other, probably in the range of
90-110 degrees apart.
So if you're using "pencil style" small diaphragm condenser mic's, you get an
arrangement that looks like a "V" with the capsule ends of the mic's
together. Run that into two channels on your console and pan hard left and
right.Having the capsules together like that helps keep the phase of the sound
coherent, and then the directionality of the mic's gives you a stereo sound
field. You can vary the angle between the mic's to determine how wide the
stereo separation sounds.
 
I actually have a few questions on connections:

1. I have an old Radio Shack Highball mic. If
I changed the connector from 1/4" to an XLR,
would this improve the signal I would get from this mic?

2. I've seen "high impedence" or "low impedence" refenced in various places. What's considered what? Is 50ohms low and as a consequence 300ohms high? What is the threshold when something becomes high-impedence?

3. I'd like to take a direct line out of my guitarists' effects processor. He's using the left out to his amp. If I take a line from the right out into a direct box with a 50ohm 1/4" in, and out 300ohm output (XLR), can this go into an XLR mic input of a mixer?

Hopefully I made sense in asking all of this.Thanks everyone for their input.
 
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