Newsgroups: rec.video.production,sci.engr.television.broadcast
Subject: Re: Who on earth still use unbalanced RCA audio? WHY??
References: <[email protected]>
"ZACHARY R. TOMCICH"  writes:

> I'm an audio engineer doing a fairly sophisticated video installation at a
> large roadhouse-type theatre.  Right now i'm shopping for some audio
> follow video switchers, RF modulators, signal Amps, etc.  It's a pretty
...
> Anyway i'm specing out some equipment, and i am ABSOLUTELY HORRIFIED that
> i'm finding broadcast quality components with unbalanced RCA plugs!  

Unbalanced auudio connections usign RCA plugs seem to be here to stay in
most of the audio/video  systems, even though good balanced interconnections
using XLR connectors are superior in many ways. The fact seems that
if you are putting up any large AV system, you always end up having
RCA cables here and there, enven though you would not want them.

> Who in their right mind would EVER use such a thing?  Why?  

They are cheap, they are widely supported and work quite OK for
small systems. But for large systems unbalanced interconnections
and RCA connectors are pain in the ass because of their tendency
to pick up hummign noise and because theit poor reliabity.

> What's wrong with the broadcast world?  

Gap between consumer, semipro and pro equipments is just dissapearing
with good and bad consequences. 

> While i have the option of purchasing balanced audio I/O's on some of
> these broadcast pieces of equipment, it's only available on select models-
> naturally none of the ones that i'm looking for.  I've looked at
> manufactors from Ocean Matrix, Kramer, and Comprehensive.  All of these
> companies had unbalanced RCA plugs as the standard audio I/O jacks on most
> of their products.  As a result, i'm going to have to switch many of my
> balanced audio channels to unbalanced to process along side my video
> signals.  What a major bugger!

That's a major bugger you are right. There are matrixes with
balanced connections, but they are harder to get and propably much
more expensive. I have seen such thign somewhere, but I don't
remeber any particulat brand.

> As an audio engineer i'm totally puzzled, confused, and utterly horrified!  
> Is there really a TV studio out there that still uses unbalanced audio for
> anything?  

Yes. Even some newest broadcasting studios have unbalanced audio
connections here and there for connections to some equipments
with unbalanced interfaces. 

> Why?  

Practially when you are putting up the system, you just can't
get all equipments having balancd audio connection in them.
In reality you end up having to still have some unbalanced
connections for connecting some equipments to your system.

> There must be a lot of them, because otherwise why would
> a majority of the components use unbalanced audio.  

The fact of life is that even though you try to keep everything
balanced, you end up having unbalanced connections somewhere.
Ledd unbalanced connections in large broadcaster professional
systems (only few of them for some effect processors and some VCRs etc),
but for smaller systems like small cable TV studios or small
video editing systems you easily end up having half or even
more than that of the audio interconnections unbalanced.

> Maybe i'm just checking out the wrong manufactorers?

Maybe. Maybe an Internet search on the companies
which have their products on-line woudl hep
to find such thing. For example search
http://www.google.com/search?q=balanced+audio+video+matrix

Gives links top many pages with this kind of products listed.
For example the second link http://www.vtx.co.uk/info.htm
seems to have matrix audio/vidoe switches with balanced stereo
audio connectors.

> If there is indeed any professional broadcast house out there that
> actually uses RCA audio jacks for ANYTHING, please fess up and explain why
> you would ever use such a horrible sounding audio standard.  

RCA connectors sound OK if the connectors are in good condition and
transmission distance is only few meters. And if there are no
groundloops and powerful noise sources nearby, the connection
can be even quite usable noise free. The reliabity oof those
connections is not the best, but is quite usable with good
connectors if those RCA connections don't need to be connectd
and disconnected too often (those connectors wear out quite quicly..)

For anything longer connections than few meters and for any harder
use I recommend using balanced interconnections. They are the way to go
best performance an trouble-free installation. 

If the equipment is just besides the mixing desk, then unbalanced
connections are usually usable. If the equipment is further away,
then going to balanced connections saves from many headaches!

> Everything that's ever used in the proaudio world has to be balanced,
> and that's for a very good reason.  

There is very good reason to use balanced interconnections. They
work well from anyhign from microphone level signals to line level
interconnections without too much trouble. Unbalanced are in some
rare cases, but building a klarge system using them is just
like asking for problems and noise to enter the system!

> Balanced Audio sound perfect no matter what the
> length, it's immune to all sorts of noise and ground loops (as long as it
> stays balanced), and it has a very low noise floor.  None of this is true
> for the vastly inferior sounding unbalanced audio.

True. Unfortunately not all balanced equipments fullfill all of
those promises. The balanced system should be practically immune
to the groundloop problems and magnetic interference, but
unfortunately not all equipments are that immune.

Audio isndustry has given some bad name for balanced connections
by f**ked up two things in balanced connections:

1. That stupid pin 2 and 3 diagreement. Some manufacturers used
   pin 2 hot+ and some other pin 3 hot+. This has caused lots
   of confusion and problems on signal phase. Unfortunately
   nowadays the manufacturers have settled up for same standard.

2. Grounding parctices inside equipments have been impelemnted
   in many equipments in so stupid ways that ground loop humming
   can enter the system. The mistake has been to ground pin 1
   to the sensitive audio signal ground insted of case ground!
   This grounding practices mistakes have made some equipments
   quite sensitive to ground loop problems. Not balancing or
   input transformer does help if the noise in groudn wire
   enters to the senitive parts of the audio euqipment circuitry!

Anyway the balanced conenctions is very much superior
to the any unbalanced connections, which is still adequate
for some applications (like home hifi systems).

Here is some more information on the mistakes that has been
made on balanced connection impelemntations:

Good and bad balanced connections
Balanced interconnection systems used in professional audio world are
naturally very good at rejecting noise problems. The shield grounded
on both ends of the cable to equipment cases provides a very good
shields agains RF interference and electric fields. The blaanced
narure of the signals will very effectively eliminate the effect of
small potential differences between the audio equipments. The twisted
narure of the wires is good at reducing the effect of noise from the
magnetic field. 

Because those design choises, a balanced audio interconnection should
be quite much free of any ground loop problems when the whole system
is done using balanced inteconnections. And if there is need to
connect anything unbalanced to such system, those should be connected
using DI-boxes and isolation transformers. This should provide a hum
free operation for equipments. 

Unfortunately in real life the situation is not so simple. Many audio
manufacturers, conciously or unconsciously, connect balanced cable
shields (pin 1 in XLR connector, sleeve on 6.3 mm jack) to audio
signal ground instead of the equipment case ground where is is
suppored to be originally connected. The result of this design choise
is that any currents induced int the shield modulte the ground where
the shield is terminated. This also modultes the signal referenced to
that ground and the result is typically annoying humming noise. 

Unfortuantely the practice of connecting noisy cable shields to audio
ground is very widely spread. This improper arrangement of shield
grounds amazingly sometimes achieves somewhat acceptable
performance. It performs well in many stadard qudio equipment bench
test, but tge peformance on the field can be quite much varying. This
means that getting good performance from such system need quite much
testing and tweaking including ground lifts and isolation
transformers. 

The hum and buzz problems with too many balanced equipments with
signal grounded shields habe given balanced equipments a bad
reputation. This has created great confusion among system designers
and users. Unfortunatley this is the situation where we have to live
in. 

The truth of a balanced interconnection is that a properly designed
and built balanced interconnection is very much better than any
unbalanced interconnection in rejecting humming noise. Properly
dessigned balanced interconnection means that for fully balanced
operation the signal wires should be well impedance balanced and the
shield of the cable should connect to the chassis ground the the point
of entry. 

> Nobody should ever use unbalanced audio for anything other than
> headphones!  

Unbalanced audio should belong to only for headphones, intercom
lines and home hifi systems. Not for any serious professional
audio systems.

> Balanced audio (+4 dB) should be used exclusively in all
> professional and broadcast settings.  Given the enormous price tag that
> comes with most broadcast quality video equipment- why would anybody
> choose to use unbalanced audio?  

Some quesses for reasons
- save few pennies on cables
- you have wider selection of equipments if you don't insist
  everything to be balanced
- because of stupidity of ignorance (it worked well at my home hifi,
  lets use it here also)
- it is easier to find equipments with unbalanced connections
- when you use unbalanced connections you can drop in some not
  so professional equipments if needed...
- when many users demand unbalanced connectiosn and don't want
  to pay extra for balanced (don't see the benefits), manufacturers
  don't put ba�anced because it would make equipments more expensive 

> I thought civilization has moved beyond unbalanced audio. 

Civilization has not moved beyond unbalanced audio.
That practice seems to be here to stay.

> So please, PLEASE, for fuck's sake, JUST SAY NO TO UNBALANCED AUDIO!

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/