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Balanced 1/4" to Unbalanced RCA / stereo jack connection. Please explain 8-)
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| blacknoizybox |
A little intro..
Well, now that i've bought turntables and stuff for mixing i finally decided to try myself in music production. First thoughts were: 1) soundcard 2)studio speakers 3) midi keys. Anyways I decided not to buy speakers since I cant afford 350 bucks for 1 piece (KRK RP8/Yamaha HS80 in mind), Im more prone to buy good studio headphones like AKG K-701
 (assumingly having one 1/4" male jack)
So here's a few points I would really like to understand..
Here is what I want to get:
Question 1: How do I connect my headphones (having 1 male 1/4" jack) to a soundcard having separate L and R 1/4" outputs?
Question 2: As you can see from the M-Audio 192 picture there are 3 pairs of 1/4" balanced connections. One pair (red+white) is definitely INPUT (L+R). Are the other two pairs (red(R)+white(L)) OUTPUTS? i mean does M-Audio 192 have 2 stereo outputs or am I not getting something. I surfed M-Audio's website and it says:
-2 balanced analog inputs (1/4” TRS) (1 R+W pair)
- 2 balanced analog outputs (1/4” TRS) (1 R+W pair)
what is the purpose of the 3-rd pair??
Question 3: How do I connect M-Audio's 1/4" balanced INPUT/OUTPUT to mixer's RCA INPUT/OUTPUTS if neccessary..? |
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| mysticalninja |
| whats the difference between balanced/unbalanced? |
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| blacknoizybox |
| quote: | Originally posted by dj_palm
its gonna be okay. just ask the dealers what u need and they get it for you. dont mind balansed or unbalansed it works either way. if ur equipment (later) has balansed outs then think about stuff. where are u planning to connect your headfones btw? |
TO THE SOUNDCARD!!! thats why im asking you people how do i do it when there's 2 seperate 1/4 female jacks out and only 1 1/4 (1/8) male from the headphones :) |
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| SgtFoo |
ideally you should connect the i/o cables from the soundcard to a mixer or even just a monitor matrix to get a headphone feed from the mixer or matrix, rather than the card directly.
rememeber, 2 of your i/o are digital as well.... 2 in 2 out.
psst...
if you wanna go the other way... you could also get a Y-cable that does 2 TRS balanced males to 1 TRS stereo headphone female |
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| rulzz |
Q1: just use stereo spliter backwards you'll still need a pair of short TRS cables though
Q2: its actually pair of MAIN outs, pair of Monitor Outs and PAir of INs (i have this card)
Q3: don't bother cuz any signal coming from the mixer will be unbalanced |
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| Derivative |
| quote: | Originally posted by mysticalninja
whats the difference between balanced/unbalanced? |
Electronic balancing is a method of reducing the effect of signal attenuation and line noise using a phasing trick.
An unbalanced line consists of 2 wires - the line that carries the positive signal and the ground. If you look at a 1/4" TS unbalanced cable and open it up you will notice the signal line is connected to the Tip, the ground is connected to the Sleave. (TS = Tip/Sleave)
As the signal travels along the length of the wire it attenuates. Or if it is not shielded properly you can pick up interference from other electrical or RFI sources or even other wires crossing its path at right angles.
A Balanced line works differently and consists of 3 wires - the line which carries the positive (in phase) signal, the line which carries the same signal with its polarity reversed - i.e. the negative (anti phase) signal and the ground. If you open up a 1/4" TRS balanced cable, you will notice that the tip has a divider on it which separates it into 2 parts. The positive line is connected to the Tip. The negative line is connected to the Ring. The Sleave as always is grounded. Hence TRS = Tip/Ring/Sleave. In an XLR connection, you have a separate pin for the positive, negative and ground lines.
You can convert a balanced line to an unbalanced line but you lose the electronic balancing process. Basically you have a completely unbalanced line.
A 1/4" TRS to 1/4" TS jack to jack connection would have the negative + ground lines connected to the sleave of the unbalanced end. The positive line goes to the Tip. Easy.
What is electronic balancing?
The reason balanced cables carry the signal both in phase and in anti phase is part of a trick.
Both ends of the cable need to be balanced and you need inputs/outputs that can can accept balanced lines (otherwise it wont read the anti phase signal and nothing happens).
Ok. As mentioned before, the signal attenuates as it travels along the length of wire. The longer the wire, the greater the attenuation. Keeping calbe runs short minimuses this but doesn't stop RFI interference.
In a balanced system you send the signal from the output stage both in phase and in anti phase. Both signals travel along the length of the wire and pick up interference along the way. For whatever reason. Cable crosstalk, RFI etc. whatever. Whatever noise is picked up by the in phase signal is also in phase. Whatever noise the anti phase signal picks up is also in phase with the anti phase signal. When both signals reach the input stage at the other end, The anti phase signal has its polarity reversed so it is completely in phase. This puts the attenuated noise difference out of phase.
What this means is you have:
Positive line: in phase signal + in phase noise
Negative line: anti phase signal + in phase noise
Reverse the polarity of the negative line at the input stage and you get...
Positive line: in phase signal + in phase noise
Negative line: in phase signal + anti phase noise
As you know, if you sum 2 identical signals that are in opposite phase you get total destructive phasing. IF you sum 2 identical signals in phase you get an amplitude spike.
Both the positive and negative (phase reversed) lines are summed at the input stage and the difference is cancelled by destructive phasing whilst amplifying the original signal.
For many reasons this process is never perfect. For one, the signal is degrading over the length of the wire but it makes more sense to think of a signal that has noise added to it. Secondly, any interference that is picked up will not be totally symmetrical on both lines. However, balancing does work, and the summed result at the end allows you to have a much hotter signal. A balanced system can easily run a few decibels louder than an unbalanced system and you NEVER get a ground loop.
Golden rules of building a signal chain: Shield everything. Ground all sleaves. Balance wherever possible. |
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