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system picks up Spanish radio - Help

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Anonymous
June 23, 2005 1:33:15 PM

Archived from groups: rec.audio.pro (More info?)

Hi,

I just started reading this group - even found a pair of mics in the
first day at a good price. It seems a very helpful bunch.

I am an amatuer live sound engineer - I've got basic training, and have
been reading a lot, testing a lot, and figuring out the rest by asking
around.

I've helped a local set up a club type of environment in his basement
(big house - basement fits about 200 standing with room to spare). We
have had a number of problems that I think are related to wiring. The
house is close to 100 years old, but the electrical running to the
basement is only about 3 yrs, and fully grounded.

We have two problems running sound that may be linked.

First - the system seems to be picking up local spanish radio - always
the same station, and noticeable when no signal is being sent to the
PAs and monitors

Second - We get a horrible buzz from DIs unless the ground is lifted

I'd appreciate any insight into findindg the source of the problem, or
any workarounds you would suggest.

Thanks,

E
Anonymous
June 23, 2005 4:35:57 PM

Archived from groups: rec.audio.pro (More info?)

Thanks everyone - ive got a lot to go on.

- E
Anonymous
June 23, 2005 4:45:15 PM

Archived from groups: rec.audio.pro (More info?)

evansgroove@gmail.com <evansgroove@gmail.com> wrote:
>
>We have two problems running sound that may be linked.
>
>First - the system seems to be picking up local spanish radio - always
>the same station, and noticeable when no signal is being sent to the
>PAs and monitors
>
>Second - We get a horrible buzz from DIs unless the ground is lifted

Check out the FAQ on the subject of ground loops.

And lifting grounds on DIs is just fine, that's why they have that
little switch on them. The reason you have a DI is so that you can
lift grounds and avoid creating loops.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Related resources
Anonymous
June 23, 2005 9:11:20 PM

Archived from groups: rec.audio.pro (More info?)

<evansgroove@gmail.com> wrote in message
news:1119544395.451460.254820@z14g2000cwz.googlegroups.com...

> First - the system seems to be picking up local spanish radio - always
> the same station, and noticeable when no signal is being sent to the
> PAs and monitors

What kind of board are you using? Brand, model? Powered or unpowered? Does
the station go away when all the faders are down? Does its level or sound
change when you move cables (including power cables) around?

> Second - We get a horrible buzz from DIs unless the ground is lifted

Are the things you have plugged into the DIs (presumably instruments on
stage) on the same AC circuit as the sound system? If not, they should be.
Does everything on stage have grounded plugs? If not, it should (death
hazard).

Peace,
Paul
Anonymous
June 23, 2005 9:58:37 PM

Archived from groups: rec.audio.pro (More info?)

<evansgroove@gmail.com> wrote in message news:1119544395.451460.254820@z14g2000cwz.googlegroups.com...
> Hi,
>
> I just started reading this group - even found a pair of mics in the
> first day at a good price. It seems a very helpful bunch.
>
> I am an amatuer live sound engineer - I've got basic training, and have
> been reading a lot, testing a lot, and figuring out the rest by asking
> around.
>
> I've helped a local set up a club type of environment in his basement
> (big house - basement fits about 200 standing with room to spare). We
> have had a number of problems that I think are related to wiring. The
> house is close to 100 years old, but the electrical running to the
> basement is only about 3 yrs, and fully grounded.
>
> We have two problems running sound that may be linked.
>
> First - the system seems to be picking up local spanish radio - always
> the same station, and noticeable when no signal is being sent to the
> PAs and monitors
>
> Second - We get a horrible buzz from DIs unless the ground is lifted
>
> I'd appreciate any insight into findindg the source of the problem, or
> any workarounds you would suggest.
>
> Thanks,
>
> E


How is the room wiring interfaced with the mixing console? Panels in the
wall or pre-assembled snake head... and if the latter, is it home made or
a pre-assembled snake?

I have found (time after time) that if a single connector is wired incorrectly
as pertains to *any* of the pins, and is plugged into the console, that the
moment a device is plugged into that - including sometimes just the mixer -
that you will be creating a loop antenna.

Having experienced this on multiple ocassions, I think you have an *audio*
cable wiring issue which probably has little to nothing to do with the AC.
(Although in reality, the can't be totally discounted, but isn't worth the worry
until you do some other checking)

I assume that this is a nearby AM radio station.

Also, the same question applies to each and every cable that you are
using for both microphones and interfacing with outboard gear. If *any*
of them are wired incorrectly and in use, you stand a good chance of
inducing the RF problem. Were all your cables preassembled or are
*any* of them home made? Each and every cable that is in use (or to
be used) should be completely checked out.

You should *not* just automatically have a 'buzz' from your DI boxes.
This is also caused, at least 85% of the time, by badly wired cabling or
cabling that has a open/short problem... likely an open if it's not just
improperly wired.

There's usually only one formula for finding and curing this problem,
and that is to *completely disconnect* all of the interface wiring. You
can start the troubleshooting as you disassemble your setup, by listening
to see if the problem stops at any point in your removal of cables. Start
with the interfaces to the outbaord gear, as there are actually the least
suspect. Eliminate each interface cable from the entire system until
you have nothing but the console and the outputs to power. If you still
have the radio, the problem is either in the mixer or the cabling to the
power. If the radio is gone, then start reassembling the system *one
wire at a time* until the problem recurs and then fix the problem cable(s).

I suggest that while the cables are off, that each one be physically
examined as well as put on a cable tester before re-using.

There's a very small chance, but a chance none-the-less, that it could
be a wiring issue inside a microphone or a DI, but no where near as
likely as a cable issue.

--
David Morgan (MAMS)
http://www.m-a-m-s DOT com
Morgan Audio Media Service
Dallas, Texas (214) 662-9901
_______________________________________
http://www.artisan-recordingstudio.com
June 23, 2005 9:58:38 PM

Archived from groups: rec.audio.pro (More info?)

On Thu, 23 Jun 2005 17:58:37 GMT, "David Morgan \(MAMS\)"
<mams@NOSPAm-a-m-s.com> wrote:

>I have found (time after time) that if a single connector is wired incorrectly
>as pertains to *any* of the pins, and is plugged into the console, that the
>moment a device is plugged into that - including sometimes just the mixer -
>that you will be creating a loop antenna.

I've seen places where you just plug a mixer into the AC and connect
the speakers and you get RF with no mics plugged in.
Anonymous
June 23, 2005 11:48:31 PM

Archived from groups: rec.audio.pro (More info?)

"Julian" <JulianPAdamsNo@SpamHotmail.Com> wrote in message news:a63mb1pugc14fjvkj3ugb5hg4uf1k5cm4q@4ax.com...
> On Thu, 23 Jun 2005 17:58:37 GMT, "David Morgan \(MAMS\)"
> <mams@NOSPAm-a-m-s.com> wrote:
>
> > I have found (time after time) that if a single connector is wired incorrectly
> > as pertains to *any* of the pins, and is plugged into the console, that the
> > moment a device is plugged into that - including sometimes just the mixer -
> > that you will be creating a loop antenna.
>
> I've seen places where you just plug a mixer into the AC and connect
> the speakers and you get RF with no mics plugged in.

That pretty well means a defective (or way too poorly designed) desk
or a similar problem with the amp. This could easily be cold solder
joints in the I/O stages of either device.... very similar to a bad cable
in symptoms.

DM
June 24, 2005 3:42:51 AM

Archived from groups: rec.audio.pro (More info?)

On Thu, 23 Jun 2005 19:48:31 GMT, "David Morgan \(MAMS\)"
<mams@NOSPAm-a-m-s.com> wrote:

>That pretty well means a defective (or way too poorly designed) desk
>or a similar problem with the amp. This could easily be cold solder
>joints in the I/O stages of either device.... very similar to a bad cable
>in symptoms.

Naw. Not necessarily bad cables or cold solder joints or even bad
design. You have no idea if the building wiring is good in the OP's
venue or what the ambient RF field is like in that neighborhood
either. RF interference is a real problem around high powered
transmitters. That's why the FCC requires that when you build a new
transmitter that EVERY complaint over the initial period after
installation MUST be individually addressed. I know of situations
where radio stations were forced to buy individual consumers new
telephones, TV's stereos, clock radios, etc., because the old ones
they owned now had problems after they put up their new tower.

1) Some mixers are just more immune to RF then others. I know a
student radio station in Bellevue WA where the AM tower that
broadcasts Spanish Radio a mile or two away has a tendency to leak
into everything. In most places I was able to fix it with improving
wiring and better grounding as you suggest. I had an old Ward Beck
mixer in the control room and everything was finally OK in that room
except the DJ mic channel on the main mixer. I swapped channel strips
and slots and other mic strips into different channels and they all
had RF. Line inputs were fine. Finally went with an external mic pre
and problem disappeared. Since then I've had 2 other mic pre's and
another mixer, no problems either. it was the channel strip that was
the weak link, but since I had extras and tried several and every one
of them was prone, it was the strip's design, not a broke piece or a
cold joint. It was an expensive piece too in it's day, not a cheap
design. Certain pieces are designed more immune than others
irrespective of price.

2) A high powered FM station in town has a poor grounding system.
I've spent a long time at that site with a senior RF engineer where
my station's transmitter is also located and he has pointed out to me
the why high power transmitter is not grounded properly. I've also
run live PA at several venues in that neighborhood with different PA's
over the course of 20 years and the best you can hope for is to keep
the RF down, you can never eliminate it. You get a buzz in the
speakers, which I believe is his AM component modulating the AC wiring
and then you can hear his FM station coming through at low volume too.
Same problem in several venues, different PA's. I have a couple of
pals who all have the same problem with their PA gear in that
neighborhood. All of our stuff ain't broke.

3) I was hired to install a sound system at a grade school where an FM
transmitter was on the roof. Their existing equipment was unusable
ever since the high school put their new transmitter up there. the
first thing I did was brought in several new mixer / amps and played
around with them to see which one was the most RF immune to begin
with. I sold them the one that had the least RF problems and then ran
cables in grounded conduit, made sure all chassis's were grounded and
used torriods on all cables as well. they ended up with a useable
system. Not badly design equipment, bad cables or cold solder joints
here either. Just a hostile environment, which could be the OP's
problem too.

Three strikes, you're out.

Julian
Anonymous
June 24, 2005 1:51:43 PM

Archived from groups: rec.audio.pro (More info?)

We used to set up a remote TV truck at the local high school and run a
snake from the auditorium or gym, and get ungodly RFI from an AM
station (1410) about a half mile away. The mixer was a Mackie 1604 (an
early one, from before the VLXPRO upgrade.) A mixer with preamps highly
succeptible to RFI.

Hmmm. Long wire (snake), preamp (Mackie)...that's an AM receiver, isn't
it?

We found a solution. When the snake fan (XLR males) was disconnected
from the truck, the RFI stopped. So I tried an isolation transformer on
each input (XLR-XLR, 600ohm) and it worked.
Anonymous
June 25, 2005 4:45:16 AM

Archived from groups: rec.audio.pro (More info?)

"Julian" <JulianPAdamsNo@SpamHotmail.Com>...

> Three strikes, you're out.

Julian... FWIW, I agree with 99% of what you say and have experienced
most of it first hand; but on equal footing, I don't think you can rule out the
cable/connector issue any more than I can rule out your observations.

So would you start by checking the wiring or building a Faraday cage?

;-)


DM
June 25, 2005 4:45:17 AM

Archived from groups: rec.audio.pro (More info?)

On Sat, 25 Jun 2005 00:45:16 GMT, "David Morgan \(MAMS\)"
<mams@NOSPAm-a-m-s.com> wrote:

>So would you start by checking the wiring or building a Faraday cage?
>
>;-)

Always the wiring first, yes. I just got the impression since the OP
had 2 problems that there was something hostile in the environment

Cheers,

Julian
Anonymous
June 25, 2005 9:31:52 AM

Archived from groups: rec.audio.pro (More info?)

"Julian" <JulianPAdamsNo@SpamHotmail.Com> wrote in message news:p hmpb19fbbk3489im657cujqimlhp5gkrv@4ax.com...
> On Sat, 25 Jun 2005 00:45:16 GMT, "David Morgan \(MAMS\)"
> <mams@NOSPAm-a-m-s.com> wrote:
>
> >So would you start by checking the wiring or building a Faraday cage?
> >
> >;-)
>
> Always the wiring first, yes. I just got the impression since the OP
> had 2 problems that there was something hostile in the environment
>
> Cheers,
>
> Julian


I only tend to jump quicker at cables than AC due to a recent experience.

About nine years ago (I was posting here then) I took over a small studio
that was only 1.2 miles from a 50,000 watt AM radio transmitter. The old
converted wooden frame house was 40+ years old, and until we added a
30 amp circuit for the digital tape machine and an isolated ground, there
had been nothing in the building other than 2-conductor romex. I had to
star ground the control room and deal with lots of little modifications to
audio cabling on both balanced & unbalanced and +4 & -10 connections.
The mixer was a D&R 4000 running +4 UNbalanced ! Fortunately, the
D&R was superb in it's RF rejection, and so was the Mitsubishi X-400.

I also inherited a good percentage of the pre-existing client base who
had grown accustomed to hearing the Texas Rangers play or the news
talk programming. When I finally tore into all of the audio lines from
the main room and iso booths to the control room... I found three jacks
which had been wired incorrectly, and merely plugging them into the
console would bring on the AM. Plugging a mic or DI into any of those
jacks would essentially turn the radio ON through those lines... clear
as a bell at about -30. Some of those old-timer clients thought I was
some sort of wizard, because they had been working there through
several owner/operators that had all failed to remove the radio and
thus limited the total number of usable connectors to just 17. Fixing
it meant we could do more instruments in a single pass. Others were
upset that they could no longer get a cue mix with radio so they could
keep up with the daily baseball game. <g>

You're quite correct however, that given the other symptom with the DI,
there could be an AC wiring issue, but the OP did say that the basement
wiring was essentially new and fully grounded. (Of course, the way some
electrical work is done these days, that really doesn't mean much does it?).

DM
June 25, 2005 9:31:53 AM

Archived from groups: rec.audio.pro (More info?)

On Sat, 25 Jun 2005 05:31:52 GMT, "David Morgan \(MAMS\)"
<mams@NOSPAm-a-m-s.com> wrote:

>I only tend to jump quicker at cables than AC due to a recent experience.

Yes, wires first. Still being that close to a high powered AM can be
very tricky. They like to build them in low elevation areas where the
ground conduction is good.

Julian
Anonymous
June 25, 2005 9:33:50 AM

Archived from groups: rec.audio.pro (More info?)

"Julian" <JulianPAdamsNo@SpamHotmail.Com> ...

> I just got the impression since the OP
> had 2 problems that there was something hostile in the environment

Quite possibly. Here's an addendum to my previous post...

http://www.krld.com/show.cfm?content=transmitter&title=...



DM
Anonymous
June 26, 2005 11:19:57 PM

Archived from groups: rec.audio.pro (More info?)

<blackburst@aol.com> wrote:
>
> We found a solution. When the snake fan (XLR males) was disconnected
> from the truck, the RFI stopped. So I tried an isolation transformer
> on each input (XLR-XLR, 600ohm) and it worked.


Is a 600 ohm load enough to keep most modern mics happy?

--
"It CAN'T be too loud... some of the red lights aren't even on yet!"
- Lorin David Schultz
in the control room
making even bad news sound good

(Remove spamblock to reply)
Anonymous
June 27, 2005 10:35:06 AM

Archived from groups: rec.audio.pro (More info?)

Lorin David Schultz wrote:
> <blackburst@aol.com> wrote:
> >
> > We found a solution. When the snake fan (XLR males) was disconnected
> > from the truck, the RFI stopped. So I tried an isolation transformer
> > on each input (XLR-XLR, 600ohm) and it worked.
>
>
> Is a 600 ohm load enough to keep most modern mics happy?

It seems to. We used EV 635s. Any port in a storm! We got the same
sound either way, except that the isos killed the RFI. My boss thought
I was a hero. (Of course, it was me who installed the Mackie in the
truck to begin with...)
Anonymous
June 29, 2005 1:16:59 PM

Archived from groups: rec.audio.pro (More info?)

When I was in high school in Columbus GA, my Fender Super Reverb
occassionaly picked up Radio Havana.
Anonymous
June 30, 2005 8:05:16 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> >BTW, how do you distribute your output? I usually use a standard
> >video/audio DA, like an Ocean Matrix, but it uses unbalanced RCAs (of
> >course, a lot of stuff at this level uses RCAs, too, like VCRs,
> >Servers, CD and DVD recorders and even cable modulators!) I'm looking
> >for ideas. I'll probably send the DA output to 1/4' on the side panel,
> >and a straight set of XLRs out from the Mackie to the panel.
>
> There are plenty of balanced audio DAs out there. A call to your local
> broadcast supply will probably turn up a bunch of used ones. Another
> nifty thing to have are the multi-winding transformers from Audisar and
> Sescom. You connect one primary to the output of the console, and you
> now have four secondaries that can go to outlets on the side panel. You
> lose either level in the process or output impedance, but that's no big
> deal. If you short one secondary, you lose only a couple dB in the others
> so the isolation is pretty good. Cheaper than a DA and it gives you
> transformer isolation for when you're dealing with untrustworthy feeds.
> --scott

We try, in our vehicles, to provide the right signal to the right
device at the right level and impedance. The maddening thing is that
there are so many types of signals and connectors. Low end pro video
decks are all RCA/-10, as are economical CD recorders, cassette
recorders, DVD recorders. The damn little Canopus converters are
RCA/-10. The cable modulators we interface with are inscrutable. I
THINK they prefer 600ohm/+4, but I'm not sure. A few pro video decks
use XLR/+4, but not many.

I end up installing two DAs, one RCA/-10 and XLR+4, and both interior
and exterior "in/out panels" with BOTH sets of connectors. Shheesh.

I think this is an article for Recording, if it hasn't been done
(Scott? Mike? Paul?): Why can't we settle on ONE standard for line and
one standard for mic?

It's the same damn thing in video. RCA, BNC,
SDI/component/Y-C/composite, F connectors for RF. I must have 19
different crimpers and cutters.

I suppose I should be happy that we don't use UHF connectors any more.
Anonymous
July 1, 2005 12:17:16 PM

Archived from groups: rec.audio.pro (More info?)

blackburst@aol.com <blackburst@aol.com> wrote:
>
>We try, in our vehicles, to provide the right signal to the right
>device at the right level and impedance. The maddening thing is that
>there are so many types of signals and connectors. Low end pro video
>decks are all RCA/-10, as are economical CD recorders, cassette
>recorders, DVD recorders. The damn little Canopus converters are
>RCA/-10. The cable modulators we interface with are inscrutable. I
>THINK they prefer 600ohm/+4, but I'm not sure. A few pro video decks
>use XLR/+4, but not many.

This being the way the world is, I figure the easiest thing to do is to
distribute everything as balanced +4 lines. When you need an unbalanced
line at -10, you use a pad and an adaptor. The big advantage of this
is that since you have a balanced line into the adaptor, you can break
the ground at the adaptor to avoid potential ground loops.

>I think this is an article for Recording, if it hasn't been done
>(Scott? Mike? Paul?): Why can't we settle on ONE standard for line and
>one standard for mic?

There is one standard! It's +8! Well, everybody _used_ to use it in
broadcast.

>It's the same damn thing in video. RCA, BNC,
>SDI/component/Y-C/composite, F connectors for RF. I must have 19
>different crimpers and cutters.
>
>I suppose I should be happy that we don't use UHF connectors any more.

Hey, I still have S-PDIF distribution on UHF around here, mostly because
I had a lot of UHF stuff that the TV guys were throwing out at about the
time I was installing S-PDIF.....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!