Audio Mixer

Audio Mixer

Hi,

Can anyone recommend a stereo audio mixer? The immediate and primary
purpose of the same will be to mix the output from three microphones.
It will be good if I had the ability to direct the output one or both
output channels.

The need is to record small public meetings commencing with some live
music (piano) followed by a talk.

However, at some point I would like to be able to mix turntable and
line inputs at home. It seems wasteful to buy two mixers when one
might suffice. For this secondary purpose I need two turntable inputs
and/or two or three line inputs. Switchable turntable/line inputs
would be acceptable.

Output will be to a Behringer UCA202 and a Notebook computer.

Many thanks for your input to my thought process!

Adrian

Re: Audio Mixer

Adrian wrote:
>
> Hi,
>
> Can anyone recommend a stereo audio mixer? The immediate and primary
> purpose of the same will be to mix the output from three microphones.
> It will be good if I had the ability to direct the output one or both
> output channels.
>
> The need is to record small public meetings commencing with some live
> music (piano) followed by a talk.
>
> However, at some point I would like to be able to mix turntable and
> line inputs at home. It seems wasteful to buy two mixers when one
> might suffice. For this secondary purpose I need two turntable inputs
> and/or two or three line inputs. Switchable turntable/line inputs
> would be acceptable.
>
> Output will be to a Behringer UCA202 and a Notebook computer.
>
> Many thanks for your input to my thought process!
>
> Adrian

I feed a Behringer UB1204-PRO directly into a Dell notebook mic jack,
which remarkably doesn't seem to mind it, at low volume.

It seems like a nice mixer, though I prefer the older and now-unavailable
models with the wall wart power supplies, as they generate less RFI
than the newer switching supply ones. But it doesn't matter, if you
don't use them right next to radios.

It doesn't seem to come with a wiring diagram, so you're left extrapolating
from older models that do come with them, as to what goes through what control
to where.
--
rhhardin@mindspring . com

On the internet, nobody knows you're a jerk.

Re: Audio Mixer

On Aug 31, 12:53 pm, Ron Hardin <rhhar...@mindspring . com > wrote:
> Adrian wrote:
>
> > Hi,
>
> > Can anyone recommend a stereo audio mixer? The immediate and primary
> > purpose of the same will be to mix the output from three microphones.
> > It will be good if I had the ability to direct the output one or both
> > output channels.
>
> > The need is to record small public meetings commencing with some live
> > music (piano) followed by a talk.
>
> > However, at some point I would like to be able to mix turntable and
> > line inputs at home. It seems wasteful to buy two mixers when one
> > might suffice. For this secondary purpose I need two turntable inputs
> > and/or two or three line inputs. Switchable turntable/line inputs
> > would be acceptable.
>
> > Output will be to a Behringer UCA202 and a Notebook computer.
>
> > Many thanks for your input to my thought process!
>
> > Adrian
>
> I feed a Behringer UB1204-PRO directly into a Dell notebook mic jack,
> which remarkably doesn't seem to mind it, at low volume.
>
> It seems like a nice mixer, though I prefer the older and now-unavailable
> models with the wall wart power supplies, as they generate less RFI
> than the newer switching supply ones. But it doesn't matter, if you
> don't use them right next to radios.
>
> It doesn't seem to come with a wiring diagram, so you're left extrapolating
> from older models that do come with them, as to what goes through what control
> to where.
> --
> rhhar...@mindspring . com
>
Thanks Ron,

I have located the more recent Xenyx 1204, which seems to fit the bill
very well.

Adrian

Re: Audio Mixer

Adrian wrote:
> Thanks Ron,
>
> I have located the more recent Xenyx 1204, which seems to fit the bill
> very well.

You'll also need a bunch of 3.5mm to 1/4" adapters, in various combinations
of stereo and mono, and a couple for RCA as well.

Then you'll find you get enormous AC hum when you connect to your computer,
owing to a ground loop. Put a Radio Shack ground loop isolator in that line
(cat 270-054). I keep a bunch of them around to isolate every different thing
that's plugged in on AC mains.
--
rhhardin@mindspring . com

On the internet, nobody knows you're a jerk.

Re: Audio Mixer

Ron Hardin wrote:
>
> Adrian wrote:
> > Thanks Ron,
> >
> > I have located the more recent Xenyx 1204, which seems to fit the bill
> > very well.
>
> You'll also need a bunch of 3.5mm to 1/4" adapters, in various combinations
> of stereo and mono, and a couple for RCA as well.
>
> Then you'll find you get enormous AC hum when you connect to your computer,
> owing to a ground loop. Put a Radio Shack ground loop isolator in that line
> (cat 270-054). I keep a bunch of them around to isolate every different thing
> that's plugged in on AC mains.

Oh, and finally some brush-on Deoxit, to keep the adapters working. I get mine
here * w w w .partsexpress . com /pe/showdetl.cfm?&Partnumber=341-215

A tiny bottle lasts forever. It fixes everything, from battery charger terminals
to audio connectors to mains plugs on high current devices that get hot (plug in
and out until the contacts come out clean).
--
rhhardin@mindspring . com

On the internet, nobody knows you're a jerk.

Re: Audio Mixer

On Sep 4, 5:36 am, Ron Hardin <rhhar...@mindspring . com > wrote:
> Ron Hardin wrote:
>
> > Adrian wrote:
> > > Thanks Ron,
>
> > > I have located the more recent Xenyx 1204, which seems to fit the bill
> > > very well.
>
> > You'll also need a bunch of 3.5mm to 1/4" adapters, in various combinations
> > of stereo and mono, and a couple for RCA as well.
>
> > Then you'll find you get enormous AC hum when you connect to your computer,
> > owing to a ground loop. Put a Radio Shack ground loop isolator in that line
> > (cat 270-054). I keep a bunch of them around to isolate every different thing
> > that's plugged in on AC mains.
>
Is that true even if I utilize the USB link into my Notebook?

> Oh, and finally some brush-on Deoxit, to keep the adapters working. I get mine
> here * w w w .partsexpress . com /pe/showdetl.cfm?&Partnumber=341-215
>
> A tiny bottle lasts forever. It fixes everything, from battery charger terminals
> to audio connectors to mains plugs on high current devices that get hot (plug in
> and out until the contacts come out clean).
> --
Thanks, I will check this out.

Adrian

Re: Audio Mixer

Adrian wrote:
> > > Then you'll find you get enormous AC hum when you connect to your computer,
> > > owing to a ground loop. Put a Radio Shack ground loop isolator in that line
> > > (cat 270-054). I keep a bunch of them around to isolate every different thing
> > > that's plugged in on AC mains.
> >
> Is that true even if I utilize the USB link into my Notebook?

Yes, it's a problem in the connecting audio cable. The computer and the audio components
don't have quite the same idea of what ground potential is. The slight difference is made up
by a current down the ground shield of the audio cable. There's a slight voltage drop
across the shield as a result, and this voltage drop is shared with the audio input circuit.

So you hear the slight ground difference in the audio signal, as AC hum.

An isolation transformer breaks the ``DC'' path in the audio cable, so there is no
shared current between power and audio circuits.

No hard trying it without, but if you get a hum, that's why.

--
rhhardin@mindspring . com

On the internet, nobody knows you're a jerk.

Re: Audio Mixer



Ron Hardin wrote:

> Adrian wrote:
> > > > Then you'll find you get enormous AC hum when you connect to your computer,
> > > > owing to a ground loop. Put a Radio Shack ground loop isolator in that line
> > > > (cat 270-054). I keep a bunch of them around to isolate every different thing
> > > > that's plugged in on AC mains.
> > >
> > Is that true even if I utilize the USB link into my Notebook?
>
> Yes, it's a problem in the connecting audio cable. The computer and the audio components
> don't have quite the same idea of what ground potential is.

That's the traditional reason for 'hum loops'.

In this case the problem is made worse but the use of switching power supplies (certainly in the
computer) and in some audio gear (I'm fairly certain the Behringer model mentioned also has one).
These swiching power supplies have filters on the ac power input that injects a noise current
into the ground conductor. This messes up your grounding arrangements very effectively.

Graham

Re: Audio Mixer


"Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote in message
news:46DE5ED4.EF6C2D0D@hotmail . com ...
>
>
> Ron Hardin wrote:
>
>> Adrian wrote:
>> > > > Then you'll find you get enormous AC hum when you connect to your
>> > > > computer,
>> > > > owing to a ground loop. Put a Radio Shack ground loop isolator in
>> > > > that line
>> > > > (cat 270-054). I keep a bunch of them around to isolate every
>> > > > different thing
>> > > > that's plugged in on AC mains.
>> > >
>> > Is that true even if I utilize the USB link into my Notebook?
>>
>> Yes, it's a problem in the connecting audio cable. The computer and the
>> audio components
>> don't have quite the same idea of what ground potential is.
>
> That's the traditional reason for 'hum loops'.
>
> In this case the problem is made worse but the use of switching power
> supplies (certainly in the
> computer) and in some audio gear (I'm fairly certain the Behringer model
> mentioned also has one).
> These swiching power supplies have filters on the ac power input that
> injects a noise current
> into the ground conductor. This messes up your grounding arrangements very
> effectively.

I've always been under the impression that the simple presence of a hard
chassis ground was all it took to pretty well guarantee a ground loop, if
there was a second hard chassis ground anyplace in the equipment that was
attached to the PC. IOW, the switching power supply might have made the
ground loop more obnoxious-sounding, but it would be there regardless.

Re: Audio Mixer



Arny Krueger wrote:

> "Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote
> > Ron Hardin wrote:
> >> Adrian wrote:
> >
> >> > > > Then you'll find you get enormous AC hum when you connect to your
> >> > > > computer, owing to a ground loop. Put a Radio Shack ground loop
> isolator in
> >> > > > that line (cat 270-054). I keep a bunch of them around to isolate
> every
> >> > > > different thing that's plugged in on AC mains.
> >> > >
> >> > Is that true even if I utilize the USB link into my Notebook?
> >>
> >> Yes, it's a problem in the connecting audio cable. The computer and the
> >> audio components don't have quite the same idea of what ground potential
> is.
> >
> > That's the traditional reason for 'hum loops'.
> >
> > In this case the problem is made worse but the use of switching power
> > supplies (certainly in the
> > computer) and in some audio gear (I'm fairly certain the Behringer model
> > mentioned also has one).
> > These swiching power supplies have filters on the ac power input that
> > injects a noise current
> > into the ground conductor. This messes up your grounding arrangements very
> > effectively.
>
> I've always been under the impression that the simple presence of a hard
> chassis ground was all it took to pretty well guarantee a ground loop, if
> there was a second hard chassis ground anyplace in the equipment that was
> attached to the PC.

For this to be the case, there has either to be some source of electromagnetic
induction ( like the stray field from a transformer) imposing itself on a
connecting wire or a current intentionally dumped to ground (as with the EMI
filters). Or, not likely in the context of equipment used in a single room, a
different earth potential at the various power sockets.


> IOW, the switching power supply might have made the
> ground loop more obnoxious-sounding, but it would be there regardless.

The mere presence of a loop doesn't of itself generate any hum. The loop simply
provides a path that's a perfect 'shorted turn' for a magnetic field to create a
current in.

You can in fact very easily have a 'hum loop' like that *inside* a piece of
equipment. I've measured potential differences of the order of tens of uV
between different parts of a steel chassis caused by electromagnetic induction
from the stray field of a large power transformer inside the equipment for
example.

Graham

Re: Audio Mixer


"Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote in message
news:46DEC3C2.17E1BE15@hotmail . com ...
>
>
> Arny Krueger wrote:
>
>> "Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote
>> > Ron Hardin wrote:
>> >> Adrian wrote:
>> >
>> >> > > > Then you'll find you get enormous AC hum when you connect to
>> >> > > > your
>> >> > > > computer, owing to a ground loop. Put a Radio Shack ground loop
>> isolator in
>> >> > > > that line (cat 270-054). I keep a bunch of them around to
>> >> > > > isolate
>> every
>> >> > > > different thing that's plugged in on AC mains.
>> >> > >
>> >> > Is that true even if I utilize the USB link into my Notebook?
>> >>
>> >> Yes, it's a problem in the connecting audio cable. The computer and
>> >> the
>> >> audio components don't have quite the same idea of what ground
>> >> potential
>> is.
>> >
>> > That's the traditional reason for 'hum loops'.
>> >
>> > In this case the problem is made worse but the use of switching power
>> > supplies (certainly in the
>> > computer) and in some audio gear (I'm fairly certain the Behringer
>> > model
>> > mentioned also has one).
>> > These swiching power supplies have filters on the ac power input that
>> > injects a noise current
>> > into the ground conductor. This messes up your grounding arrangements
>> > very
>> > effectively.
>>
>> I've always been under the impression that the simple presence of a hard
>> chassis ground was all it took to pretty well guarantee a ground loop, if
>> there was a second hard chassis ground anyplace in the equipment that was
>> attached to the PC.

> For this to be the case, there has either to be some source of
> electromagnetic
> induction ( like the stray field from a transformer) imposing itself on a
> connecting wire or a current intentionally dumped to ground (as with the
> EMI
> filters).

There always seem to be incidental em fields kicking around places were AC
power is being used.

> Or, not likely in the context of equipment used in a single room, a
> different earth potential at the various power sockets.

Agreed. I've seen a few volts of ground potential differences in adjacent
rooms on different circuits.

>> IOW, the switching power supply might have made the
>> ground loop more obnoxious-sounding, but it would be there regardless.

> The mere presence of a loop doesn't of itself generate any hum. The loop
> simply
> provides a path that's a perfect 'shorted turn' for a magnetic field to
> create a
> current in.

Agreed.

> You can in fact very easily have a 'hum loop' like that *inside* a piece
> of
> equipment. I've measured potential differences of the order of tens of uV
> between different parts of a steel chassis caused by electromagnetic
> induction
> from the stray field of a large power transformer inside the equipment for
> example.

That's one reason why we have separate signal grounds, even inside the
chassis.

Re: Audio Mixer



Arny Krueger wrote:

> "Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote
>
> > You can in fact very easily have a 'hum loop' like that *inside* a piece
> > of equipment. I've measured potential differences of the order of tens of uV
>
> > between different parts of a steel chassis caused by electromagnetic
> > induction from the stray field of a large power transformer inside the
> equipment for
> > example.
>
> That's one reason why we have separate signal grounds, even inside the
> chassis.

This used to be very popular but is inherently incompatible with good EMC
practice.

I use chassis ground as my reference and I'm VERY careful about stuffing current
into the ground ( i.e I avoid it like the plague ). As a last resort, I also
make some internal connections differential/balanced, which of course entirely
eliminates the complication of questionable ground potentials.

Graham

Re: Audio Mixer


"Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote in message
news:46DECBB8.FA6E38AE@hotmail . com ...
>
>
> Arny Krueger wrote:
>
>> "Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote
>>
>> > You can in fact very easily have a 'hum loop' like that *inside* a
>> > piece
>> > of equipment. I've measured potential differences of the order of tens
>> > of uV
>>
>> > between different parts of a steel chassis caused by electromagnetic
>> > induction from the stray field of a large power transformer inside the
>> equipment for
>> > example.
>>
>> That's one reason why we have separate signal grounds, even inside the
>> chassis.
>
> This used to be very popular but is inherently incompatible with good EMC
> practice.

Interesting.

> I use chassis ground as my reference and I'm VERY careful about stuffing
> current
> into the ground ( i.e I avoid it like the plague ). As a last resort, I
> also
> make some internal connections differential/balanced, which of course
> entirely
> eliminates the complication of questionable ground potentials.

Interesting.

Re: Audio Mixer

In message <46DECBB8.FA6E38AE@hotmail . com >, Eeyore
<rabbitsfriendsandrelations@hotmail . com > writes
>
>
>Arny Krueger wrote:
>
>> "Eeyore" <rabbitsfriendsandrelations@hotmail . com > wrote
>>
>> > You can in fact very easily have a 'hum loop' like that *inside* a piece
>> > of equipment. I've measured potential differences of the order of
>> >tens of uV
>>
>> > between different parts of a steel chassis caused by electromagnetic
>> > induction from the stray field of a large power transformer inside the
>> equipment for
>> > example.
>>
>> That's one reason why we have separate signal grounds, even inside the
>> chassis.
>
>This used to be very popular but is inherently incompatible with good EMC
>practice.
>
>I use chassis ground as my reference and I'm VERY careful about
>stuffing current
>into the ground ( i.e I avoid it like the plague ). As a last resort, I also
>make some internal connections differential/balanced, which of course entirely
>eliminates the complication of questionable ground potentials.
>
>Graham
>
>
I have to agree there Graham. If you're going to have a ground in a
piece of equipment, make sure there's only one, and make sure that
everything that connects to it has the lowest impedance path you can
manage.
--
Chris Morriss

Re: Audio Mixer

In article <1188589284.767185.139710@r23g2000prd.googlegroups . com >,
Adrian <adrian_h_hudson@yahoo . com > wrote:
> Can anyone recommend a stereo audio mixer? The immediate and primary
> purpose of the same will be to mix the output from three microphones.
> It will be good if I had the ability to direct the output one or both
> output channels.

> The need is to record small public meetings commencing with some live
> music (piano) followed by a talk.

> However, at some point I would like to be able to mix turntable and
> line inputs at home. It seems wasteful to buy two mixers when one
> might suffice. For this secondary purpose I need two turntable inputs
> and/or two or three line inputs. Switchable turntable/line inputs
> would be acceptable.

Sounds like you're into a disco mixer if you want cartridge inputs.
Personally I'd go for a Behringer or Mackie and use external pickup
pre-amps.

For recording speech you want a mixer with a half decent
compressor/limiter.

--
*Never miss a good chance to shut up *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.