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Cough Switch & Mic Splitter = Hiss

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Anonymous
August 31, 2005 12:24:17 AM

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

In order to get the announcers microphone to the program mixer as well
as the intercom system we must employ a mic level DA. Aparently a
passive splitter with a "Cough switch would kill both feeds not just
the program line.

Problem is this: The Mic level DA we have creates a hiss in the audio
chain. Our Mixer is a Mackie, and it was said that the op-amp inputs on
the board don't mix well with transformered ballanced outputs of this
Mic DA.

So far i've tried lifting the shields on source or destination. I've
tried strapping a ground between the DA and the Chasis of the mixer (
the DA we got runs off a WALL WART ) It seems like a reasonably decent
piece of equipment, except for the hiss.

Any Ideas would help, thanks
nick
Anonymous
August 31, 2005 6:30:59 AM

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

It's a "Mic Level" DA, like an active splitter.
Anonymous
August 31, 2005 9:03:44 AM

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

nmm wrote:

> In order to get the announcers microphone to the program mixer as well
> as the intercom system we must employ a mic level DA. Aparently a
> passive splitter with a "Cough switch would kill both feeds not just
> the program line.

Could you put a preamp close to the mic and then split the output of
that, with a mute function on one leg? You could do that with a 1202.

> Problem is this: The Mic level DA we have creates a hiss in the audio
> chain. Our Mixer is a Mackie, and it was said that the op-amp inputs on
> the board don't mix well with transformered ballanced outputs of this
> Mic DA.

I don't understand how the mackie's inputs could be interacting with the
DA's outputs. Is that reversed, or am I missing something?

--
ha
Related resources
Anonymous
August 31, 2005 11:27:07 AM

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

nmm wrote:
> In order to get the announcers microphone to the program
> mixer as well as the intercom system we must employ a mic
> level DA. Aparently a passive splitter with a "Cough switch
> would kill both feeds not just the program line.

Depends on the splitter. Well-designed ones can take a dead
short of one output without affecting the other one.
Depends on the mute switch. The simple kind just shorts the
balanced line, but it can be done differently.
Sure, it is possible that a cheap splitter and a conventional
switch might behave as you describe. But that is not a
condemnation of all splitters and mute switches.

> Problem is this: The Mic level DA we have creates a
> hiss in the audio chain.

Sounds like a cheap marginally-designed unit. But since
you didn't identify it, we can only speculate.

> Our Mixer is a Mackie, and it was said that the op-amp
> inputs on the board don't mix well with transformered
> ballanced outputs of this Mic DA.

Unlikely. Sounds like an excuse from a non-technical
sales-droid.
Anonymous
August 31, 2005 12:32:28 PM

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

nmm <voxman@arvotek.net> wrote:
>In order to get the announcers microphone to the program mixer as well
>as the intercom system we must employ a mic level DA. Aparently a
>passive splitter with a "Cough switch would kill both feeds not just
>the program line.

What is this mike level DA? Who makes it?

> Problem is this: The Mic level DA we have creates a hiss in the audio
>chain. Our Mixer is a Mackie, and it was said that the op-amp inputs on
>the board don't mix well with transformered ballanced outputs of this
>Mic DA.

That doesn't make all that much sense, as far as noise goes. It might
make for ringing and termination issues, but that's not what you are
complaining about.

>So far i've tried lifting the shields on source or destination. I've
>tried strapping a ground between the DA and the Chasis of the mixer (
>the DA we got runs off a WALL WART ) It seems like a reasonably decent
>piece of equipment, except for the hiss.

What is it?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 31, 2005 2:21:52 PM

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

"nmm" <voxman@arvotek.net> wrote in message
news:1125458657.571454.283830@g14g2000cwa.googlegroups.com
> In order to get the announcers microphone to the program
> mixer as well as the intercom system we must employ a mic
> level DA. Aparently a passive splitter with a "Cough
> switch would kill both feeds not just the program line.
>
> Problem is this: The Mic level DA we have creates a hiss
> in the audio chain. Our Mixer is a Mackie, and it was
> said that the op-amp inputs on the board don't mix well
> with transformered ballanced outputs of this Mic DA.

Sounds like a defensive move on the part of the supplier of
the Mic DA.

> So far i've tried lifting the shields on source or
> destination.

Unlikely to help with hiss.

> I've tried strapping a ground between the DA
> and the Chasis of the mixer ( the DA we got runs off a
> WALL WART )

Unlikely to help with hiss.

>It seems like a reasonably decent piece of
> equipment, except for the hiss.

That's like saying that the Titanic was a reasonbly decent
ship except for the design, the materials and the captain's
leadership.
Anonymous
August 31, 2005 7:11:26 PM

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

nmm wrote:
> In order to get the announcers microphone to the program mixer as well
> as the intercom system we must employ a mic level DA.

Do you mean AD?


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
Anonymous
August 31, 2005 7:13:40 PM

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

"nmm" <voxman@arvotek.net> wrote in message
news:1125510819.118526.166950@o13g2000cwo.googlegroups.com...
> The unit is an "ATI" nanoamp DMA-103
> http://www.atiguys.com/?fa=products&category=6#

It claims -124dB noise. Are you sure you have it configured
right? Not running it at line level with mic level ins/outs or
something silly like that?

>
> The cough switch imade by "Pro-Co" , and called a "Short Stop".
> http://www.procosound.com

Almost certainly the kind that just shorts the audio signal.
Even passive mic splitters should be designed to take
one output shorted without affecting the other output.
Or maybe this was the kind of splitter where the main
feed is straight through, and the additional output is
derived from it. If you short the main output, the other
output likely dies with it. Putting the switch on the
alternate output would likely prevent the "mute-all"
problem.
Anonymous
August 31, 2005 9:12:02 PM

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

"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:D f59ub11s1a@enews4.newsguy.com...
>
>
> nmm wrote:
>> In order to get the announcers microphone to the program mixer as well
>> as the intercom system we must employ a mic level DA.
>
> Do you mean AD?

DA = Distribution Amplifier.
Perhaps a more common term in video than audio?
Anonymous
September 1, 2005 12:23:34 AM

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

SSJVCmag wrote:
> On 8/31/05 8:12 PM, in article df5h0i$ptc$1@news01.intel.com, "Richard
> Crowley" <richard.7.crowley@intel.com> wrote:
>
> >
> > "Bob Cain" <arcane@arcanemethods.com> wrote in message
> > news:D f59ub11s1a@enews4.newsguy.com...
> >>
> >>
> >> nmm wrote:
> >>> In order to get the announcers microphone to the program mixer as well
> >>> as the intercom system we must employ a mic level DA.
> >>
> >> Do you mean AD?
> >
> > DA = Distribution Amplifier.
> > Perhaps a more common term in video than audio?
>
> Not for ME! then 'gin I came up in network broadcast...
> World runs on punchdown and DA's...
>
> Mic-level DA's though are not what I found as 'common'... Except as media
> press mults



Yes by "DA" I meant "Distribution Amplifier".


And we did recieve an ADC punchdown block in the same order as this..
Which is a Type 2, though i told the intigrator who is working with us
we want all Type 4 punchdowns, far more robust, but i digress.
Anonymous
September 1, 2005 12:27:50 AM

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

Richard Crowley wrote:
> "nmm" <voxman@arvotek.net> wrote in message
> news:1125510819.118526.166950@o13g2000cwo.googlegroups.com...
> > The unit is an "ATI" nanoamp DMA-103
> > http://www.atiguys.com/?fa=products&category=6#
>
> It claims -124dB noise. Are you sure you have it configured
> right? Not running it at line level with mic level ins/outs or
> something silly like that?
>

I've actually tried both. Stepping it up to line levels on the output
is done by moving jumpers inside. Setting of the input level is done by
a DIP switch. It just seems to give me stronger level on the Hiss
coming back into the main mixer.

> >
> > The cough switch imade by "Pro-Co" , and called a "Short Stop".
> > http://www.procosound.com
>
> Almost certainly the kind that just shorts the audio signal.
> Even passive mic splitters should be designed to take
> one output shorted without affecting the other output.
> Or maybe this was the kind of splitter where the main
> feed is straight through, and the additional output is
> derived from it. If you short the main output, the other
> output likely dies with it. Putting the switch on the
> alternate output would likely prevent the "mute-all"
> problem.


I was just considering that the "Mute all" would be problem if i were
to run a passive splitter, instead of the DA. This works fine for that.
Anonymous
September 1, 2005 3:18:05 AM

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

On 8/31/05 6:11 PM, in article df59ub11s1a@enews4.newsguy.com, "Bob Cain"
<arcane@arcanemethods.com> wrote:

>
>
> nmm wrote:
>> In order to get the announcers microphone to the program mixer as well
>> as the intercom system we must employ a mic level DA.
>
> Do you mean AD?

That or Distribution Amp
Anonymous
September 1, 2005 4:26:57 AM

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

SSJVCmag wrote:
> On 8/31/05 6:11 PM, in article df59ub11s1a@enews4.newsguy.com, "Bob Cain"
> <arcane@arcanemethods.com> wrote:
>
>
>>
>>nmm wrote:
>>
>>>In order to get the announcers microphone to the program mixer as well
>>>as the intercom system we must employ a mic level DA.
>>
>>Do you mean AD?
>
>
> That or Distribution Amp

Ah, thanks. The question makes a great deal more sense in
the correct context. :-)


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
Anonymous
September 1, 2005 4:33:48 AM

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

On 8/31/05 8:12 PM, in article df5h0i$ptc$1@news01.intel.com, "Richard
Crowley" <richard.7.crowley@intel.com> wrote:

>
> "Bob Cain" <arcane@arcanemethods.com> wrote in message
> news:D f59ub11s1a@enews4.newsguy.com...
>>
>>
>> nmm wrote:
>>> In order to get the announcers microphone to the program mixer as well
>>> as the intercom system we must employ a mic level DA.
>>
>> Do you mean AD?
>
> DA = Distribution Amplifier.
> Perhaps a more common term in video than audio?

Not for ME! then 'gin I came up in network broadcast...
World runs on punchdown and DA's...

Mic-level DA's though are not what I found as 'common'... Except as media
press mults
Anonymous
September 1, 2005 10:17:43 AM

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

Here's what your problem looks like to me, after looking at the description
of the DA on the ATI website. You're running the mic into the distribution
amp. You're then running the distribution amp's outputs into mic-level
inputs on the mixer and the other system.

The problem is, the output of the distribution amp is designed to run at
line level, not mic level. (To make it put out mic level, and not clip the
hell out of the following gear, you must have the gain cranked way low.) The
output stages of the DA are not particularly low-noise circuits, as it's
assumed they'll be handling line-level signals. So you're putting a
not-particularly-quiet DA output stage with a teeny-weeny signal running
through it into a microphone preamp, which amplifies the signal and the
noise.

Try running the output of the DA into the line input of the mixer. You'll
need to crank up the gain on the DA to do that, but once you do I bet the
hiss goes down.

Peace,
Paul
Anonymous
September 1, 2005 10:59:43 PM

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

Paul Stamler wrote:
> Here's what your problem looks like to me, after looking at the description
> of the DA on the ATI website. You're running the mic into the distribution
> amp. You're then running the distribution amp's outputs into mic-level
> inputs on the mixer and the other system.
>
> The problem is, the output of the distribution amp is designed to run at
> line level, not mic level. (To make it put out mic level, and not clip the
> hell out of the following gear, you must have the gain cranked way low.) The
> output stages of the DA are not particularly low-noise circuits, as it's
> assumed they'll be handling line-level signals. So you're putting a
> not-particularly-quiet DA output stage with a teeny-weeny signal running
> through it into a microphone preamp, which amplifies the signal and the
> noise.
>
> Try running the output of the DA into the line input of the mixer. You'll
> need to crank up the gain on the DA to do that, but once you do I bet the
> hiss goes down.

Yeah, and it is really typical mistake for non-audio guys to set
things up like that. Fox News Radio had similar hiss the affiliates
were complaining about, troubleshooting I found the same
line-level-into-mic-level-input kind of mistake, they had a Symmetrics
Micpre running line level into the mic input of a Mackie 1402. A
video guy on the Tascam forums was complaining about bad audio from his
VTRS on a DM24, so I just blindly guessed he had patched his VTR line
outs into the micpre ins. Yep. The temptation of an XLR out and an
XLR in is just to much for some guys to resist! Even at FNC, the
Calrec Sigma I used to mix on was interfaced with the Studio PA console
similarly, they patched the line level outs of the Sigma into the mic
pre inputs of the PA Board and thought since the pads were in it was
ok. Besides degrading the audio quality for whatever reason, what
happens when 48 volts phantom gets engaged on the micpre channels? You
send the voltage back up into the group line and direct outputs of the
Sigma mixer is what, which is IMO not a good thing. I have an older
Sony DAT that had it's output caps blow up by being interface
incorrectly like that and getting phantom into it's outputs - doh!

( But it might be be better not to mention the technical mistakes
to your powers that be - trust me on that. It would not be unusual to
find oneself censured rather that credited for pointing out such things
in some highly charged situations. Maybe just fix it quietly and move
on.)

BTW, Nick might use *two* mics on the talent, one for the cough
switched Program mic and one for the intercom/Producer's prefade listen
only. It does work - just make sure everyone agrees it's the talent's
fault when he kills his mic and he bleeds through an open guest's mic
who is sitting right next to him...

Will Miho
NY Music and TV/Audio Post Guy
"The large print giveth and the small print taketh away..." Tom Waits
Anonymous
September 1, 2005 11:19:30 PM

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

Paul Stamler wrote:

> Here's what your problem looks like to me, after looking at the description
> of the DA on the ATI website. You're running the mic into the distribution
> amp. You're then running the distribution amp's outputs into mic-level
> inputs on the mixer and the other system.

> The problem is, the output of the distribution amp is designed to run at
> line level, not mic level. (To make it put out mic level, and not clip the
> hell out of the following gear, you must have the gain cranked way low.) The
> output stages of the DA are not particularly low-noise circuits, as it's
> assumed they'll be handling line-level signals. So you're putting a
> not-particularly-quiet DA output stage with a teeny-weeny signal running
> through it into a microphone preamp, which amplifies the signal and the
> noise.

> Try running the output of the DA into the line input of the mixer. You'll
> need to crank up the gain on the DA to do that, but once you do I bet the
> hiss goes down.

And note that while Mackie labels the XLR inputs as mic/line, they have
in many of their mixers 14 dB additional gain built-into that input, so
you can't really attenuate a +4 line level to fit properly. Using the
TRS jacks bypasses that additional gain.

--
ha
Anonymous
September 2, 2005 6:18:00 AM

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

hank alrich wrote:
> Paul Stamler wrote:
>
> > Here's what your problem looks like to me, after looking at the description
> > of the DA on the ATI website. You're running the mic into the distribution
> > amp. You're then running the distribution amp's outputs into mic-level
> > inputs on the mixer and the other system.
>
> > The problem is, the output of the distribution amp is designed to run at
> > line level, not mic level. (To make it put out mic level, and not clip the
> > hell out of the following gear, you must have the gain cranked way low.) The
> > output stages of the DA are not particularly low-noise circuits, as it's
> > assumed they'll be handling line-level signals. So you're putting a
> > not-particularly-quiet DA output stage with a teeny-weeny signal running
> > through it into a microphone preamp, which amplifies the signal and the
> > noise.
>
> > Try running the output of the DA into the line input of the mixer. You'll
> > need to crank up the gain on the DA to do that, but once you do I bet the
> > hiss goes down.
>
> And note that while Mackie labels the XLR inputs as mic/line, they have
> in many of their mixers 14 dB additional gain built-into that input, so
> you can't really attenuate a +4 line level to fit properly. Using the
> TRS jacks bypasses that additional gain.
>
> --
> ha


This was one o the first things i tried. XLR out of the Mic DA, into a
TRS connector ( Line input )on the Mackie. One figures that the TRS is
line level, and interupts the Mic Pre.. Maybe we have a Mackie 3208
that was built on a Monday morning, because that isn't the case. The
trim pot stayed at exactlty the same place; the level was exactly the
same.

Turning down the gain does make the hiss go down, but the equivelant
gain on another channel with an identical microphone, doesn't have the
hiss.
Anonymous
September 2, 2005 7:30:42 AM

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

On 1 Sep 2005 18:59:43 -0700, "WillStG" <willstg@aol.com> wrote:

> ( But it might be be better not to mention the technical mistakes
>to your powers that be - trust me on that. It would not be unusual to
>find oneself censured rather that credited for pointing out such things
>in some highly charged situations. Maybe just fix it quietly and move
>on.)

Because it's *always* your fault. Dead messenger? No prob;
next messenger.

Always the best,

Chris Hornbeck
Anonymous
September 2, 2005 11:41:39 AM

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

"nmm" <voxman@arvotek.net> wrote in message
news:1125652680.955748.237080@g47g2000cwa.googlegroups.com

> This was one o the first things i tried. XLR out of the
> Mic DA, into a TRS connector ( Line input )on the
> Mackie. One figures that the TRS is line level, and
> interupts the Mic Pre..

That is how a typical Mackie works, such as my old SR32.

>Maybe we have a Mackie 3208 that
> was built on a Monday morning, because that isn't the
> case. The trim pot stayed at exactlty the same place; the
> level was exactly the same.

That is like no console input (Mackie or other) I've ever
seen.

I think that if you tried this again, you'd get a different
result.

I can't imagine a probable wiring fault in a Mackie that
would cause this.

> Turning down the gain does make the hiss go down, but the
> equivalant gain on another channel with an identical
> microphone, doesn't have the hiss.

Well yes it doesn't have the same amp in the line.

Last night I tried something similar to where you started
out. I hooked a Rolls MP13 mic preamp (has XLR ins and outs
so this made it easy to cable) into the mic input of my
Yamaha 02R96. The source is an Audix OM-5 which is a low
output dynamic mic which requires about 50 dB gain in this
application. I set the Yamaha for about 25 dB gain and the
Rolls for about 25 dB gain. Subjectively, the results were
very quiet.
Anonymous
September 3, 2005 4:02:53 AM

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

nmm wrote:
> This was one o the first things i tried. XLR out of the Mic DA, into a
> TRS connector ( Line input )on the Mackie. One figures that the TRS is
> line level, and interupts the Mic Pre.. Maybe we have a Mackie 3208
> that was built on a Monday morning, because that isn't the case. The
> trim pot stayed at exactlty the same place; the level was exactly the
> same.
>
> Turning down the gain does make the hiss go down, but the equivelant
> gain on another channel with an identical microphone, doesn't have the
> hiss.

If you patch line level signals into micpres, it is very common
to get hiss and a degraded audio signal Nick. Not because of added
gain neccessarily, you can pad it down but there are other issues and
you still will get hiss and a degraded audio quality.

Not only in the 3 audio for video examples I
experienced/discussed in my other post did this cause problems, but
even when I have patched synthesiser level signals into micpres on
SSL's trying to get a hotter level to digital tape, it clearly degraded
the signal. Impedence problem maybe? I dunno, but experience dictates
line level outs into mic level in's is best avoided. Although I have
also had situations where RF's with mic level transformer split's
hissed badly in the monitors, but when the RF mics where switched to
line level outputs the hiss went away. They were very long cable runs
though at mic level ( a recent Kanje West gig of a buddy's I sat
through a bit of. )

Maybe the fix with the lowest profile would be inserting a DI /
line to mic transformer. But 2 mics works great, especially if you are
using 2 lavs on a clip, but you can so it with announce mics too and
use one for program and one for the intercom prefade feeds.

Will Miho
NY Music and TV/Audio Post Guy
"The large print giveth and the small print taketh away..." Tom Waits
!