Who on earth still use unbalanced RCA audio? WHY??
ZACHARY R. TOMCICH
large roadhouse-type theatre. Right now i'm shopping for some audio
follow video switchers, RF modulators, signal Amps, etc. It's a pretty
big system which will allow us to handle vast amounts of video in our
hall.
Anyway i'm specing out some equipment, and i am ABSOLUTELY HORRIFIED that
i'm finding broadcast quality components with unbalanced RCA plugs! Who
in their right mind would EVER use such a thing? Why? What's wrong with
the broadcast world?
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!
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? Why? There must be a lot of them, because otherwise why would
a majority of the components use unbalanced audio. Maybe i'm just
checking out the wrong manufactorers?
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. Everything
that's ever used in the proaudio world has to be balanced, and that's for
a very good reason. 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.
Nobody should ever use unbalanced audio for anything other than
headphones! 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?
I thought civilization has moved beyond unbalanced audio. This whole
ordeal i find to be very depressing, and is going to require many sessions
with my therapist.
So please, PLEASE, for fuck's sake, JUST SAY NO TO UNBALANCED AUDIO!
*scratches his head... *
hhhmm... perhaps i should shoot a letter of to Nancy and have her help me
with this crusade.
--
Ziggy
Richard Smedley
Richard
"ZACHARY R. TOMCICH" <ztom...@mason2.gmu.edu> wrote in message
news:8p4m6g$o...@portal.gmu.edu...
Tomi Holger Engdahl
> 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 baöanced 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/
Matt M
fact I'm not aware of any broadcast facilities in this area that use an
unbalanced audio signal. I am seeing a log of the lower end DV Cams &
Non-Linear Editing systems with unbalanced audio, but I always assumed that
these were more for the consumer/"Mom&Pop video" than actual broadcast. I
guess you could get away with using it for maybe cable spots (no slam of
cable production intended here), as they tend to be less "picky" than
stations. I personally hate unbalanced audio, but of course all of this is
just my personal opinion and what do I know?! ;-)
Matt
Tomi Holger Engdahl <th...@jolly.cs.hut.fi> wrote in message
news:lajk8cp...@jolly.cs.hut.fi...
Stuart
> i'm finding broadcast quality components with unbalanced RCA plugs! Who
> in their right mind would EVER use such a thing? Why? What's wrong with
> the broadcast world?
Who is the manufacturer/model type? Are you sure it's not some consumer
brand?
Werner Kliewer
the professional audio world, "balanced audio" cabling is to RCA jacks what
Differential SCSI is to normal SCSI. I am not sure, but I believe the new UDMA
IDE cables (80 wire) accomplish much the same effect, although with reduced
reliability because the connectors are still 40-pin.
The idea is to have a two wire pair, the difference in voltage/frequency
between them being the active signal, rather than a single signal wire matched
to an arbitrary reference. Interference, attenuation, etc. can affect the
single signal to such an extent that there are erroneous differences between
that and the arbitrary reference. When you have a two wire signal with a
differential signal, most interference, attenuation, etc. affect both equally
and in the same direction so that the difference between them remains constant
allowing much more accurate interpretation of that signal.
This is a layman's explanation of the principle and may not be electrically
precise.
In article <39b6...@wznews.webzone.net>, Richard Smedley wrote:
>
> What's "balanced audio"? ;)))
>
> Richard
>
Werner Kliewer
in Winnipeg
Jay Rose
and -- within the limits of practical equipment (we're not talking thermal
noise) -- there is nothing inherently wronger about -10 dBV vs +4 dBm. You
could even argue that the extra components required for balanced audio
(usually an additional inverting amp stage, but possibly a transformer)
degrade the sound. Incidentally, accidental phase inversions of one
channel in a pair are virtually impossible with unbalanced wiring.
Of course I'm talking short cable lengths in a controlled environment,
with good wiring practices. But it's perfectly possible to build a
professional-sounding studio using ubalanced wiring. I've done it.
In most facilities there's a definite advantage to using balanced wiring
because of its noise immunity and simplicity of grounding. And XLR
connectors are certainly more robust than phono plugs. I'd certainly opt
for an all-balanced system whereever possible.
But prejudices aside, the reason you're finding RCA audio in matrix
switchers is you're looking at units designed for the
duplicator/installed-sound market. Check any issue of Broadcast
Engineering for routers that handle balanced audio. They're more
expensive, of course.
--
Jay Rose <<jay at dplay dotcom>>
Clio/Emmy-winning Sound Designer
Want to learn audio for video? http://www.dplay.com/book
Maurice R Fleisher
> Anyway i'm specing out some equipment, and i am ABSOLUTELY HORRIFIED that
> i'm finding broadcast quality components with unbalanced RCA plugs! Who
> in their right mind would EVER use such a thing? Why? What's wrong with
> the broadcast world?
-snip-
I agree with everything you say and I speak, basically, as a now-hard-of
hearing cameraman not as a sound engineer however as an independent operator
I have a very healthy respect for the sound requirements of good production.
Pictures can be fudged to cover up errors. Bad sound is bad sound and there
is very little can be done to hide the gaping sore thumb.
My only additional comment to your abhorrence of RCA Phono connectors is
to say that 3.5mm mini audio connectors are a far worse abomination and
should be banned from ALL equipment, audio or otherwise.
Just my (crackle, crackle, break-up, crackle) two cent's worth.
Maurice
--
Maurice R Fleisher mailto:mau...@vident.u-net.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
VIDEO ENTERPRISES <http://www.vident.u-net.com>
High Wycombe. UK
Martian Welk
just because we GOTTA HAVE IT , well when they find they cant quadrouple the
price they will give on thier pricing a bit and then we will adjust
accordingly.
myself i have seen a "pro" run a "balanced" line 200 feet under 200feet of
florescent ballasts and my coaxed "line level" was clean and his
aparentally poorly balanced "balanced" line had more humm than the
florescent lights themselves.
so when some "pros/amatures" use a balanced line incorectally it could be
far worse forming a big ass huge transformer instead making the "pro" look
like an "idiot" for having spent 5-10x as much money to accomplish the same
task no better.
why does the same element setup for a microphone come for 750$ balanced and
75$ unbalanced ? Because they CAN.
i have never been in a single theatre that didnt have everything supposedly
"balanced" and still didnt have audible humm from dimmers and amps and , and
, and . the times i have not see this was when the system was brought in
from the outside kept away from the house system completly.
NO i am NOT saying that a line level wouldnt have been far worse
i am saying that it is darn expencive in both time and money and still can
have all the problems or more that these wonderfull balanced lines can have
when they arent used corectally. and being used correctally reminds me of
computers, if every one of them was used corectally no one would have a
problem would they :-) but an manuel typewritter doesnt cost 1/10th and
doesnt have to be used corectally. it just works.
this doesnt mention that once you have unbalanced because you have been a
cheapskate at one time or another, that matching balanced to unbalanced is a
juggling act that generally results in you dropping all your balls, as
somone makes off with your wallet.
after you spend that much on the camera, Who can afford audio :-)
opinions from the cheapskate
whos audio is still the best part of his video
reguarless of the horrendous un-balanced lines involved
you pay
you pay
you pay
but its just
another day
"ZACHARY R. TOMCICH" <ztom...@mason2.gmu.edu> wrote in message
news:8p4m6g$o...@portal.gmu.edu...
Mike Lambert
"glitch" swithers that have balanced in and outs (screw in type connectors,
no XLRs)
--
Mike Lambert
Quote of the minute:
"Life is like an onion, you peel off layers and sometimes you weep"
Some guy from one of the news groups I visit
"ZACHARY R. TOMCICH" <ztom...@mason2.gmu.edu> wrote in message
news:8p4m6g$o...@portal.gmu.edu...
DB
>
> I've never put anything out for broadcast using unbalanced equipment. In
> fact I'm not aware of any broadcast facilities in this area that use an
> unbalanced audio signal. I am seeing a log of the lower end DV Cams &
> Non-Linear Editing systems with unbalanced audio, but I always assumed that
> these were more for the consumer/"Mom&Pop video" than actual broadcast. I
> guess you could get away with using it for maybe cable spots (no slam of
> cable production intended here), as they tend to be less "picky" than
> stations. I personally hate unbalanced audio, but of course all of this is
> just my personal opinion and what do I know?! ;-)
>
> Matt
Matt
Do you think you can hear the difference between bal/unbal sound
quality???? {meaning freq response, quality etc not noise}. Balancing
allows longer cable runs and the possibility of less ground induced
hum/noise, but there is no sonic difference.
Dave
William Bender
not been able to find a switcher with XLR audio I/O it has all been RCA
bad news ).
William J. Bender
TV productions Instructor
Poinciana High School
2300 Poinciana Blvd.
Kissimmee, FL. 34758
Home address
3321 5th. St
St. Cloud, FL. 34769-2011
Home e-mail ben...@kua.net
Work e-mail ben...@osceola.k12.fl.us
Web www.wjbender.com
Work phone 407-870-4860 ext.348
Home phone 407-892-2104
Cell phone 407-301-7994
(Please remember that all donations can be/are tax deductible)
"ZACHARY R. TOMCICH" <ztom...@mason2.gmu.edu> wrote in message
news:8p4m6g$o...@portal.gmu.edu...
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Ira Wilner
>That is one reason that I teach my students to use a audio mixer, I to have
>not been able to find a switcher with XLR audio I/O it has all been RCA
> bad news ).
The professional signal routing switchers use the balanced audio format.
The control heads can be programmed to operate unbalanced video routers in
tandem with balanced audio routers.
Leitch comes to mind as an example of a pro video and audio router company.
--Ira
Ira Wilner
>There is absolutely nothing wrong with the "sound" of unbalanced audio,
>and -- within the limits of practical equipment (we're not talking thermal
>noise) -- there is nothing inherently wronger about -10 dBV vs +4 dBm. You
>could even argue that the extra components required for balanced audio
>(usually an additional inverting amp stage, but possibly a transformer)
>degrade the sound. Incidentally, accidental phase inversions of one
>channel in a pair are virtually impossible with unbalanced wiring.
>
>Of course I'm talking short cable lengths in a controlled environment,
I totally agree with Jay. And, indeed, it is easier to produce fabulous
audio with unbalanced line level interconnects as long as the source
impedance is kept very low.
Now, as for video gear with RCA jacks, notice that the video outputs and
inputs are already unbalanced whether they be RCA or BNC! Thus you already
have a grounding compromise of shields connecting two machines together in
most broadcast plants. The machines are therefore carefully setup, usually
in close proximity, sharing the same chassis grounds. This reduces the
ground loop noise issue for the audio feeds. If the ground loop noise was
significant, you'd have hum bars in your video too.
Ideally the video feeds should also be balanced! But the only place I've
ever encountered balanced video lines was at the telephone company. They
used to send video all around Manhattan over twisted pairs.
In the video studio of the future, all signal interconnects will be digital
and possibly optical. This would still permit single ended, unbalanced
connections but without ground loop and other noise issues.
Check out AES/EBU digital audio connections in TV facilities. They
typically do not use 3 pin XLR connectors with balanced AES-3 digital audio.
Instead they use coaxial cable, typically 75 ohm as that is the common
wiring available in the TV plant, used, of course for composite video. It
is less expensive, can utilize/share video patch panels and video routers
too.
--Ira Wilner
Mike Kujbida
(http://www.mackie.com/). You'll find a whole line of inexpensive audio
mixers (with great specs, BTW) that are fully balanced - except for the
usual tape/CD inputs. I bought my 1604 VLZ-PRO from a local music store
(best prices in the area - and a lot of bands use them). IMHO, the best
mixer for the money. Not to say that there aren't better (because there
are) but this line is damn hard to beat for the price.
Mike Kujbida
"William Bender" <ben...@kua.net> wrote in message
news:39b6f...@corp.newsfeeds.com...
Tomi Holger Engdahl
> My only additional comment to your abhorrence of RCA Phono connectors is
> to say that 3.5mm mini audio connectors are a far worse abomination and
> should be banned from ALL equipment, audio or otherwise.
> Just my (crackle, crackle, break-up, crackle) two cent's worth.
I can say the same on 3.5 mm mini audio connectors. They are
unreliable and huge pain in audio installations. Unfortunately
all major computer soundcards, PC based video editing card and
equipments designed for Internet TV brodacasting seem to have
those 3.5 mm jacks. When you have a dozen of such connections
in a large Internet broadcasting system, you can just use
gaffa tape to fasten the wires to table/computer case and pray
that they don't craccle and pop much during the broadcasting.
No can do with those connections, because that's the stuff
you get from the companies working in this field...
Other thing where 3.5 mm jack are even in worse place:
video cameras. If you are talking about any small
video camera (for example DV camera) not stricly for
broadcasting use, you very ofthen find 3.5 mm jack for
the (stereo) microphone input. Whan you want to
plug any decent microphone (some professional microphone
with XLR cable) for repoorting purposes, then only thign you
can keep thos thing to work is lots of gaffa tape to fasten
that thin cable in 3.5mm to XLR adapter and the 3.5 mm connector
itself to the camera. I really heate this kind of connectors
in this kind of use!
Ban those 3.5 mm stereo jacks in any decent audio. The
only thing where they are suitable are small portable
CD players and small radios as headphone connectors.
They are not the most realible connectors there either, but on
those applications there is nothign very critical going
on which would be messed up if sound cracles and pops.
Martian Welk
we would NOT be having this problem the cheap ass manufacturers save
themselves 1.2c per unit and you know what that means to the stockholders
1.2c dividends Horray for the stockholders Die stockholders :-)
if we have to have these things for size/weight conciderations they could at
least put in ones that Work.
replacing thier crappy plastic ones with crappy metal ones placed in a spot
on the case fixes this problem PLASTIC SUCKS
Plastic chassis suck plastic tripod mounts suck plastic doors break
plastic mounted bnc's get loose Plastic 747's crash You wouldnt drink a
beer out of plastic . were only thankfull that they havent figured a way to
make firestone tires from plastic :-)
"Tomi Holger Engdahl" <th...@jolly.cs.hut.fi> wrote in message
news:lajog20ed...@jolly.cs.hut.fi...
Richard Smedley
Richard
"Martian Welk" <T_...@hotmail.com> wrote in message
news:emQt5.175702$i5.25...@news1.frmt1.sfba.home.com...
Robert Casey
Ira Wilner wrote:
>
>
> Now, as for video gear with RCA jacks, notice that the video outputs and
> inputs are already unbalanced whether they be RCA or BNC! Thus you already
> have a grounding compromise of shields connecting two machines together in
> most broadcast plants. The machines are therefore carefully setup, usually
> in close proximity, sharing the same chassis grounds. This reduces the
> ground loop noise issue for the audio feeds. If the ground loop noise was
> significant, you'd have hum bars in your video too.
>
> Ideally the video feeds should also be balanced! But the only place I've
> ever encountered balanced video lines was at the telephone company. They
> used to send video all around Manhattan over twisted pairs.
I've seen video equipment that accepts unbalanced video with a
differential amp input stage. The center conductor/signal feeds
the positive/non-inverting input to the diff amp, and the ground
(which is isolated from the equipment chassis) of the coax
(the shield) feeds the negative/inverting input of the diff amp.
The result is that the common mode (ground loops and noise)
gets rejected, and the desired signal gets thru.
Would this work for balanced audio inputs? Or is there a transformer with
a grounded centertap on the input?
jcpop
specified are NOT Broadcast quaility venders and their ad's are full of crap
if they say they are. If I as a Chief Engineer would buy anything from a
company like Comprehensive I would be shot. Try Lietch for you routing needs
they carry a line of affordable routers that are Broadcast Quality.
Dave Stork
nearly meaningless. Everybody's equipment is "broadcast quality", even
if it's made entirely of cheap plastic and uses RCA jacks for all
audio AND video connections! :-)
The stuff you've been seeing in the catalogs is really more of the
"semi-pro" quality level, and intended for wedding/event photogs,
small project studios and guys running little post-houses based around
Video Toasters and the like. These edit suites usually reside on a
desktop and the cable runs are short, and unbalanced, low-level
(-10dBu) audio is usually not a big drawback. For real "broadcast"
equipment, look at offerings from Leitch, Utah Scientific, Pesa, etc.
Of course, these products cost quite a bit more than the semi-pro
stuff, and the extra cost might not be justified in a small
non-broadcast installation.
I agree with the original poster's sentiment that unbalanced -10dBu
audio and RCA jacks are generally to be avoided in a broadcast
facility. I'm a television engineer and I have the misfortune of
having inherited a medium-sized, low-budget operation where there is a
large installed base of consumer-type audio equipment sitting right
alongside the real broadcast-level stuff. Previous station managers,
operations personnel, self-styled directors of engineering and such,
who chose this lower-cost equipment to impress the tight-fisted
station owners, failed to take into account the added hassle and
expense of interfacing this equipment properly. If you save $200 on a
CD player, but have to buy an ATI Matchmaker or Henry Matchbox to
interface it to your system, have you really saved anything?
Luckily, for engineers in a position such as mine, consumer and pro
audio equipment can be made to co-exist reasonably well in certain
limited circumstances. If your CD and MD players are sitting right
above your mixing console, attached to it by four-foot cables, noise
pickup is not usually an issue. Assuming the "pro" and "consumer"
equipment do not share a common chassis ground, you can treat the
consumer machine's output differentially with good results in short to
medium cable runs. This is similar to the manner in which professional
video equipment uses a differential input to cancel common-mode noise
on "unbalanced" video lines. As an example, when connecting an
unbalanced RCA output to a balanced XLR input, you would connect the
RCA "+" to XLR pin 2, the RCA "-" to XLR pin 3, connect the shield to
pin 1 at the XLR end, and leave the shield floating at the RCA end. If
the two pieces of equipment _do not_ share a common chassis ground,
then the signal is balanced as far as the receiving-end equipment is
concerned.
This wiring scheme works well in instances where the LEVEL difference
between the consumer and pro gear is not a major issue. For instance,
it would work for a CD player, where the output is usually hot enough
to drive inputs intended for a level of +4dBu. For tape decks and
other such equipment that is normalized to a -10dBu level, the
situation is a bit more complicated. You need a source of low-noise
gain to bring the low-level output up to +4dBu, and a means to
attenuate the +4dBu signal down to -10 at the input end. This can be
as simple and no-cost as adjusting the input gain on a distribution
amplifier or mixing console and using a resistive attenuator at the
tape machine input, or it may be necessary to purchase (or build) a
matching device of the type described earlier.
Noise immunity has almost as much to do with the skill and knowledge
of the installer as it does with whether the audio line is balanced or
unbalanced. Overly long or improperly routed balanced lines
(especially mic-level) WILL pick up hum and noise. Balanced audio is a
powerful and useful tool, but it is not a panacea for sloppy cable
routing.
An engineer who inherits a situation such as the one I've described
will have to make creative compromises in order to achieve the best
possible performance from the equipment on hand. But if you're in the
position of building a new facility and have an adequate budget, don't
even bother with the consumer-grade stuff!
Dave Stork
New York
Ira Wilner
>Its the DAMN PLASTIC if the connectors were the metalic full ground style
>we would NOT be having this problem the cheap ass manufacturers save
>themselves 1.2c per unit and you know what that means to the stockholders
>1.2c dividends Horray for the stockholders Die stockholders :-)
>
>if we have to have these things for size/weight conciderations they could
at
>least put in ones that Work.
There is more to it than that Martian! The consumer camcorders have several
volts
DC superimposed on the mic input circuits to power cheap consumer electret
condenser
microphones. Several volts of DC on a mic input circuit that normally sees
a few millivolts of AC signal from the mic itself is asking for noise
problems, crackles etc.
Secondly, most 3.5mm jacks are directly soldered to PC boards. The solder
connection has to endure physical movement that ultimately breaks them. The
correct way, more expensive, to do it, as seen on some professional gear, is
to firmly attach the jack to the case of the device and use flexible wire
jumpers between it and the circuit board.
--Ira
Ira Wilner
Robert Casey wrote in message <39B859BB...@ix.netcom.com>...
>
>I've seen video equipment that accepts unbalanced video with a
>differential amp input stage. The center conductor/signal feeds
>the positive/non-inverting input to the diff amp, and the ground
>(which is isolated from the equipment chassis) of the coax
>(the shield) feeds the negative/inverting input of the diff amp.
>The result is that the common mode (ground loops and noise)
>gets rejected, and the desired signal gets thru.
>
>Would this work for balanced audio inputs? Or is there a transformer with
>a grounded centertap on the input?
Hi Robert. Very good catch on the floating input ground for an unbalanced
composite video input. Indeed it would work for audio and has been done
professionally. Stereo composite audio signals are fed from stereo
generators to FM broadcast exciters via single ended coaxial cable. Some
exciters and generators use floating grounds not referenced to chassis
ground to reduce ground loop noise.
Most modern sources of balanced audio use active differential direct coupled
inputs and no transformers. Today, those that do use transformers do not
use center taps to ground. That was a practice from long telephone line
days where grounding the pair without disturbing its differential balance
was a common way to reduce line noise from induced currents.
However, some microphone inputs do use what is essentially an AC grounded
center tap as the means of injecting 48 volt phantom power.
--Ira
Ira Wilner
>I'm a television engineer and I have the misfortune of
>having inherited a medium-sized, low-budget operation where there is a
>large installed base of consumer-type audio equipment sitting right
>alongside the real broadcast-level stuff. Previous station managers,
>operations personnel, self-styled directors of engineering and such,
>who chose this lower-cost equipment to impress the tight-fisted
>station owners, failed to take into account the added hassle and
Hi Dave,
When I was a kid, growing up in NYC, I had the opportunity to visit WPIX-TV.
To my horror, all of their in house cabling was unbalanced! This was back
in the late1950's.
In more recent years, I had to set up a new master control facility for a
small market TV station. The owners were very cheap. Video, audio, even
the STL setups were nightmares. And the tower crew managed to install the
directional UHF antenna facing the wrong way! That was in the mid 1970's.
Cheers,
--Ira
Martian Welk
if it stayed pc mounted it would indeed still have a easy way to break
i have not yet had trouble with using self-powered unbalanced mics with
these connections excluding the time i thought the 3rd wire on a sony was
part of a stereo pair when discarding the inbred mic for an external
connection. like you said it was power. and it sure wasnt stereo :-)
after the tech located the tiney fuse and replaced it i continued to
complete my connection by using a volt meter this time, and connected to the
two wires and had excelent sound with the self-powered microphone.
it didnt matter to me at the time that it cost 60$ (for the fuse
replacement) because the built in microphone would have cost me way more,
in crappy sound.
on those cameras for that use automatic gain was important and still
functiond well , neither being to low or cracking at the top.
having luck is important sometimes, i dont know what i would have done if
it didnt work, after the cerimonial destruction of the crappy onboard
microphone :-)
*picture cameraman with large mallot and big smile*
"Ira Wilner" <bdcs...@sover.net> wrote in message
news:zEBu5.37690$nq4.6...@news-east.usenetserver.com...