[sdiy] stereo output questions.....

[jure zitnik]

since he wrote "2 XLR cables", he obviously means balanced stereo.

again, when you say TRS, what exactly do you mean? "TRS" does not
describe a signal, it merely describes the mechanical connector. so if
you take the 6.3mm jack (male) connector with 3 contacts an look at
it:
T(ip) - the end of the jack
R(ing) - the middle section
S(leeve) - the rest, this contacts is the biggest

the other 3-contact mechanical connector is called XLR, again, it's
just a name for the connector, meant to fit on a 3-conductor (3 wire)
cable.

now you can use those 3 contacts - on a TRS or an XLR connector - and
the corresponding 3 conductors in the cable for different purposes,
but mostly the following two:

1. unbalanced stereo audio - usually TRS is used for this, i don't
think i've ever seen XLR used for stereo.
the TIP and the RING contacts are used for left and right audio
signal, the SLEEVE is used as ground for both. that way you get a
stereo signal on 3 conductor cable, with TRS jacks.

2. balanced mono audio - both TRS and XLR are commonly used here, but
TRS are usually used in studio. they are less bulky but also less
durable. on stage, you'll usually see XLR.
the idea of balanced audio is to use two "copies" of signal, using two
separate conductors, to eliminate the noise that is common to both
copies. the general idea is to send the signal and an inverted copy of
the same signal. then at the receiving end the inverted copy is
inverted again and the copies are added together, but the common noise
between the two subtracts (because of inversion). so at the end you
get the signal twice the amplitude, minus the noise. for this, you
again need 3 conductors. one for the original signal ("hot"), one for
the inverted one ("cold") and again one ground for both together.

so, which one do you need, the question is not "TRS or stereo". the
question should be first "stereo or mono", then "balanced or
unbalanced", and then "XLR or TRS".

On Thu, Nov 27, 2008 at 3:51 PM, John Mahoney <jmahoney at gate.net> wrote:
> Here are 2 ways to carry stereo signals:
>
> 1) A pair of 2-conductor cables, one for L and one for R. Each cable has a
> hot (signal) line and a ground.
> 2) One 3-conductor cable, with a hot line for L, a hot for R, and a common
> ground.
>
> 3-conductor stereo cables typically have TRS connectors. Example:
> headphones.
>
> However, TRS connectors are also used for mono, balanced cabling, which also
> has 3 wires (signal+, signal-, and ground).
>
> XLR connectors can carry stereo signals but they are usually used for
> balanced mono.
>
> When you say "stereo not TRS", do you mean separate Left and Right cables
> instead of one stereo cable?
>
> John
>
>
> At 08:47 AM 11/27/2008, Dan Snazelle wrote:
>
>> no i think i mean just plain stereo..not trs
>>
>> the guy wants to convert a stereo signal (left and right) into an adapter
>> that goes into 2 XLR cables...
>> i was pretty sure he said STEREO not TRS but he might not know the
>> difference.
>>
>> so basically if i send an inverted signal to one side and a normal to the
>> other, that is TRS?
>>
>> thanks
>
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