"Adrian" wrote in message
ups.com...
On Sep 1, 4:07 am, "Arny Krueger" wrote:
"Adrian" wrote in message

oups.com

It will be good if I had the
ability to direct the output one or both output channels.

Direct???

I want to be able to direct input from a mic. to the left of a piano
to the left stereo channel, and the right to the right. When I am
speaking I want to send the mic. input to bboth channels in even
proportions. Do I sound new to this? There is a reason for
that! :-)

These are the sorts of things that even the more basic mixers do well.

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.
--


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

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 http://www.partsexpress.com/pe/showd...number=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).
--


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

On Sep 4, 5:36 am, Ron Hardin 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
herehttp://www.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

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.

--


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

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

"Eeyore" wrote in message
...


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.

Arny Krueger wrote:

"Eeyore" 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

"Eeyore" wrote in message
...


Arny Krueger wrote:

"Eeyore" 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.

Arny Krueger wrote:

"Eeyore" 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