Delays and symetrical inputs outputs

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Delays and symetrical inputs outputs

patrick.forums.info

>>
>> Hi all,
>>
>> What is the complexity to write relevant code to introduce in a link
>
>> * a delay of a certain number of mS
>
>It's trivially simple to write an application that does this.
>
>> * a conversion of one channel into two channels ( + and - ) in order to
get
>> a symmetrical output
>> * a conversion of two channels into one channel in order to get a
>> symmetrical input
>
>If you want symmetrical ins/outs just use hardware that provides
>them. Doing this is in software is not the same thing, and it will
>fail to work correctly in almost all cases.

I know it is better to do that in hardware especially for the analogue
input. Indeed the common mode can saturate the inputs.

However it can be nice to do that by software to avoid electronic boxes and
their power supply colse to the cards.

It is probabely better than asymetrical connections ( for draft works )

Also it can be nice to have only one connection type ( the symetrical )



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Re: Delays and symetrical inputs outputs

Fons Adriaensen-2
On Sun, Jul 11, 2010 at 11:10:44PM +0200, patrick.forums.info wrote:

> Also it can be nice to have only one connection type ( the symetrical )

If on a single connector, yes. If you start using two
of them for a single signal the result will just be a
big cabling mess.

To interconnect my 'pro' gear I just need three types
of cables:

XLR-M <---> XRL-F   in all lenghts,
XLR-M <---> TRS     1.5m
XLR-F <---> TRS     1.5m

and that's it.

No if you start using two ins/outs for fake balancing
just imagine the collection of cable types you'd need.

Apart from that I have a collection of RCA <---> TRS
for the non-pro stuff such as CD player and tuner, and
one or two mini-stereo-jack <---> 2 x TRS for the MP3
player or laptop.

All of these are unbalanced, and there's *not a trace* of
hum or interference when I use them. The simple truth is
that in a home situation unbalanced connections are just
OK, and if you have problems with them that is in 99.9%
of all cases due to:

- trying to connect things that are incompatible,
- bad audio cables,
- bad mains wiring,
- or just lousy equipment.

Things are different on stage and when you are using
guitar amps. On stage just use equipment designed for
that type of situation. For guitar amps used at home
buy a decent DI-box, it will solve your problems even
if feeding an unbalanced input. If it doesn't replace
your sound card with one that works.

Ciao,

--
Je veux que la mort me trouve plantant mes choux, mais
nonchalant d’elle, et encore plus de mon jardin imparfait.
(Michel de Montaigne)
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Re: Delays and symetrical inputs outputs

John Rigg-16
On Sun, Jul 11, 2010 at 11:10:44PM +0200, patrick.forums.info wrote:
 
> Also it can be nice to have only one connection type ( the symetrical )

The reason balanced inputs are used is to reject common mode noise
and interference. Outputs do not need symmetrical voltages to take
advantage of this. They just need balanced output impedance. A
resistor of 50 to 100 ohms between the cold output terminal and ground
is usually quite sufficient. If you have an unbalanced output jack you can
make a balanced cable with an unbalanced jack plug plus an extra resistor
from the cold conductor to the jack plug ground terminal for example.

It's a waste of time adding an extra reverse polarity output as it isn't
necessary.

On the input side, an additional reverse polarity input is very unlikely
to have good common mode rejection because of the distance between inputs,
so it's a lot of effort for little benefit.

John
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