[Scott Prian]

I just upgraded my recording setup from a digital mixer to separate pre's compressors, and IO with a computer, so im still getting things straight.

I just purchased a Presonus LT (preamp), opened the box and hooked all the inserts up to compressors and sent digital via lightpipe to my MOTU 2408 PCIe I/O. The equipment is not hooked up to my computer yet by the way.

All of the channels were recognized and sounding alright... at first, till I plugged into channels 7 and 8 and I noticed theres an annoying 60 cycle buzz that doesnt change when i touch the timecode ins/outs. The buz is in every channel at higher gains but sticks out in the last two channels.

Oddly, the hum is effected by gain knobs but NOT effected by Pad. So then i used the inserts in the LT to send the analog signals to the 2408 and the hum is still there in the same channels.



Any ideas?

[Eeyore]

Scott Prian wrote:

I just upgraded my recording setup from a digital mixer to separate
pre's compressors, and IO with a computer, so im still getting things
straight.

I just purchased a Presonus LT (preamp), opened the box and hooked all
the inserts up to compressors and sent digital via lightpipe to my MOTU
2408 PCIe I/O. The equipment is not hooked up to my computer yet by the
way.

All of the channels were recognized and sounding alright... at first,
till I plugged into channels 7 and 8 and I noticed theres an annoying
60 cycle buzz that doesnt change when i touch the timecode ins/outs.
The buz is in every channel at higher gains but sticks out in the last
two channels.

Oddly, the hum is effected by gain knobs but NOT effected by Pad. So
then i used the inserts in the LT to send the analog signals to the
2408 and the hum is still there in the same channels.

Any ideas?

Yes, this happens with computer audio. I doubt computer makers will ever
care much ( one of the main problems is usually in the PSU actually ). Are
you running ALL your signals properly balanced ? That ought to fix things.
So don't use an unbalanced input monitor amp etc etc. Why it's the last 2
channels is anyone's guess but I'll bet there's 'something' different about
how the source is wired or whatever.

Forget that, except for general info. This happens when it's NOT connected
to the PC ? Sounds like internal power supply noise to me, the PSU is often
at one end. Ask for a replacement and / or contact the manufacturer.

Graham

[David Nebenzahl]

On 3/20/2009 7:49 AM Eeyore spake thus:

Scott Prian wrote:

I just upgraded my recording setup from a digital mixer to separate
pre's compressors, and IO with a computer, so im still getting things
straight.

I just purchased a Presonus LT (preamp), opened the box and hooked all
the inserts up to compressors and sent digital via lightpipe to my MOTU
2408 PCIe I/O. The equipment is not hooked up to my computer yet by the
way.

All of the channels were recognized and sounding alright... at first,
till I plugged into channels 7 and 8 and I noticed theres an annoying
60 cycle buzz that doesnt change when i touch the timecode ins/outs.
The buz is in every channel at higher gains but sticks out in the last
two channels.

Oddly, the hum is effected by gain knobs but NOT effected by Pad. So
then i used the inserts in the LT to send the analog signals to the
2408 and the hum is still there in the same channels.

Any ideas?

Yes, this happens with computer audio. I doubt computer makers will ever
care much ( one of the main problems is usually in the PSU actually ). Are
you running ALL your signals properly balanced ? That ought to fix things.
So don't use an unbalanced input monitor amp etc etc. Why it's the last 2
channels is anyone's guess but I'll bet there's 'something' different about
how the source is wired or whatever.

In other words, "I have no ****ing idea, but I'm going to pontificate
about balanced lines, etc., as is my wont."


--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
Made With Pears: Pretty good chance that pears will be detectable in
the product.
Contains Pears: One pear seed per multiple tons of product.

(with apologies to Dorothy L. Sayers)

[Scott Prian]

Any ideas?[/i][/color]

Yes, this happens with computer audio. I doubt computer makers will ever
care much ( one of the main problems is usually in the PSU actually ). Are
you running ALL your signals properly balanced ? That ought to fix things.
So don't use an unbalanced input monitor amp etc etc. Why it's the last 2
channels is anyone's guess but I'll bet there's 'something' different about
how the source is wired or whatever.

Forget that, except for general info. This happens when it's NOT connected
to the PC ? Sounds like internal power supply noise to me, the PSU is often
at one end. Ask for a replacement and / or contact the manufacturer.

Graham[/quote]

hows it going, i switched the power cable im not sure if thats what you meant, Also, i plugged in the headphones (dumb idea i understand) in the insert of the channel with nothing in the inputs, and nothing in any of the inserts, and still i can hear the hum. the unit at that point was stand alone with only power and headphones plugged into it...

but im waiting for a call from someone i can talk to from sweet water about the issue hopefully they can help too

thanks though

[Eeyore]

Scott Prian wrote:

Any ideas?

Yes, this happens with computer audio. I doubt computer makers will
ever care much ( one of the main problems is usually in the PSU actually
).
Are you running ALL your signals properly balanced ? That ought to fix
things. So don't use an unbalanced input monitor amp etc etc. Why it's the
last
2 channels is anyone's guess but I'll bet there's 'something' different
about how the source is wired or whatever.

Forget that, except for general info. This happens when it's NOT
connected to the PC ? Sounds like internal power supply noise to me, the
PSU is
often at one end. Ask for a replacement and / or contact the manufacturer.

Graham

hows it going, i switched the power cable im not sure if thats what you
meant,[/i][/color]

No, the power cable will do nothing. I'm talking about hum pickup from a
presumably internal transformer.


Also, i plugged in the headphones (dumb idea i understand) in the insert

Not a dumb idea at all.


of the channel with nothing in the inputs,

Try shorting the input or better still use a 220 ohm resistor across pins 2
and 3.


and nothing in any of
the inserts, and still i can hear the hum. the unit at that point was
stand alone with only power and headphones plugged into it...

Right so it's the analogue mic amp humming. That fits with my original idea.

Graham

[Eeyore]

David Nebenzahl wrote:

On 3/20/2009 7:49 AM Eeyore spake thus:

Scott Prian wrote:

I just upgraded my recording setup from a digital mixer to separate
pre's compressors, and IO with a computer, so im still getting things
straight.

I just purchased a Presonus LT (preamp), opened the box and hooked all
the inserts up to compressors and sent digital via lightpipe to my MOTU
2408 PCIe I/O. The equipment is not hooked up to my computer yet by the
way.

All of the channels were recognized and sounding alright... at first,
till I plugged into channels 7 and 8 and I noticed theres an annoying
60 cycle buzz that doesnt change when i touch the timecode ins/outs.
The buz is in every channel at higher gains but sticks out in the last
two channels.

Oddly, the hum is effected by gain knobs but NOT effected by Pad. So
then i used the inserts in the LT to send the analog signals to the
2408 and the hum is still there in the same channels.

Any ideas?

Yes, this happens with computer audio. I doubt computer makers will ever
care much ( one of the main problems is usually in the PSU actually ). Are
you running ALL your signals properly balanced ? That ought to fix things.
So don't use an unbalanced input monitor amp etc etc. Why it's the last 2
channels is anyone's guess but I'll bet there's 'something' different about
how the source is wired or whatever.

In other words, "I have no ****ing idea, but I'm going to pontificate
about balanced lines, etc., as is my wont."

Balancing can make HUGE differences. Has the OP done this ? And then I thought it
could be PSU placement in the unit. I've heard this effect happen in other gear.

So I have 2 good leads.

Graham

[David Nebenzahl]

On 3/21/2009 4:48 AM Eeyore spake thus:

David Nebenzahl wrote:

On 3/20/2009 7:49 AM Eeyore spake thus:

Scott Prian wrote:

All of the channels were recognized and sounding alright... at first,
till I plugged into channels 7 and 8 and I noticed theres an annoying
60 cycle buzz that doesnt change when i touch the timecode ins/outs.
The buz is in every channel at higher gains but sticks out in the last
two channels.

Oddly, the hum is effected by gain knobs but NOT effected by Pad. So
then i used the inserts in the LT to send the analog signals to the
2408 and the hum is still there in the same channels.

Any ideas?

Yes, this happens with computer audio. I doubt computer makers will ever
care much ( one of the main problems is usually in the PSU actually ). Are
you running ALL your signals properly balanced ? That ought to fix things.
So don't use an unbalanced input monitor amp etc etc. Why it's the last 2
channels is anyone's guess but I'll bet there's 'something' different about
how the source is wired or whatever.

In other words, "I have no ****ing idea, but I'm going to pontificate
about balanced lines, etc., as is my wont."

Balancing can make HUGE differences. Has the OP done this ? And then I thought it
could be PSU placement in the unit. I've heard this effect happen in other gear.

So I have 2 good leads.

How in the *world* could unbalanced inputs cause 2 channels to exhibit
hum and the others to operate normally? Assuming that all channels are
connected identically. Sounds like grasping at straws to me.


--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
Made With Pears: Pretty good chance that pears will be detectable in
the product.
Contains Pears: One pear seed per multiple tons of product.

(with apologies to Dorothy L. Sayers)

[Eeyore]

David Nebenzahl wrote:

On 3/21/2009 4:48 AM Eeyore spake thus:
David Nebenzahl wrote:
On 3/20/2009 7:49 AM Eeyore spake thus:
Scott Prian wrote:

All of the channels were recognized and sounding alright... at first,
till I plugged into channels 7 and 8 and I noticed theres an annoying
60 cycle buzz that doesnt change when i touch the timecode ins/outs.
The buz is in every channel at higher gains but sticks out in the last
two channels.

Oddly, the hum is effected by gain knobs but NOT effected by Pad. So
then i used the inserts in the LT to send the analog signals to the
2408 and the hum is still there in the same channels.

Any ideas?

Yes, this happens with computer audio. I doubt computer makers will ever
care much ( one of the main problems is usually in the PSU actually ). Are
you running ALL your signals properly balanced ? That ought to fix things.
So don't use an unbalanced input monitor amp etc etc. Why it's the last 2
channels is anyone's guess but I'll bet there's 'something' different about
how the source is wired or whatever.

In other words, "I have no ****ing idea, but I'm going to pontificate
about balanced lines, etc., as is my wont."

Balancing can make HUGE differences. Has the OP done this ? And then I thought it
could be PSU placement in the unit. I've heard this effect happen in other gear.

So I have 2 good leads.

How in the *world* could unbalanced inputs cause 2 channels to exhibit
hum and the others to operate normally?

We don't know what he has connected and how. Since he seems uninterested in responding
we probably never will.


Assuming that all channels are connected identically.

NEVER 'assume' anything ! That's where most mistakes are made.


Sounds like grasping at straws to me.

You're clueless. I notice you've avoided the PSU placement issue.

Graham

[Scott Prian]

Originally Posted by Eeyore

David Nebenzahl wrote:

On 3/21/2009 4:48 AM Eeyore spake thus:
David Nebenzahl wrote:
On 3/20/2009 7:49 AM Eeyore spake thus:
Scott Prian wrote:

All of the channels were recognized and sounding alright... at first,
till I plugged into channels 7 and 8 and I noticed theres an annoying
60 cycle buzz that doesnt change when i touch the timecode ins/outs.
The buz is in every channel at higher gains but sticks out in the last
two channels.

Oddly, the hum is effected by gain knobs but NOT effected by Pad. So
then i used the inserts in the LT to send the analog signals to the
2408 and the hum is still there in the same channels.

Any ideas?

Yes, this happens with computer audio. I doubt computer makers will ever
care much ( one of the main problems is usually in the PSU actually ). Are
you running ALL your signals properly balanced ? That ought to fix things.
So don't use an unbalanced input monitor amp etc etc. Why it's the last 2
channels is anyone's guess but I'll bet there's 'something' different about
how the source is wired or whatever.

In other words, "I have no ****ing idea, but I'm going to pontificate
about balanced lines, etc., as is my wont."

Balancing can make HUGE differences. Has the OP done this ? And then I thought it
could be PSU placement in the unit. I've heard this effect happen in other gear.

So I have 2 good leads.

How in the *world* could unbalanced inputs cause 2 channels to exhibit
hum and the others to operate normally?

We don't know what he has connected and how. Since he seems uninterested in responding
we probably never will.


Assuming that all channels are connected identically.

NEVER 'assume' anything ! That's where most mistakes are made.


Sounds like grasping at straws to me.

You're clueless. I notice you've avoided the PSU placement issue.

Graham

I did mention before about how I had no cables besides the headphones plugged in, the hum exists more as the channel 'number' increases.

By this i mean, there is little hum in 1,2,3,4 but in 5,6 theres it is enough to be bothersome, and in 7,8 it is too much to be usable.

like I said, it has nothing to do with cables im using because im not using cables at all and it still makes the noise through ADAT out and the line (tip of insert) out. I notified the salesman about it via email, he said that he would have someone call me, im assuming monday to talk about the issue...

I will repost something on any word of the problem.

[David Nebenzahl]

On 3/22/2009 12:25 AM Scott Prian spake thus:

I did mention before about how I had no cables besides the headphones
plugged in, the hum exists more as the channel 'number' increases.

By this i mean, there is little hum in 1,2,3,4 but in 5,6 theres it is
enough to be bothersome, and in 7,8 it is too much to be usable.

like I said, it has nothing to do with cables im using because im not
using cables at all and it still makes the noise through ADAT out and
the line (tip of insert) out. I notified the salesman about it via
email, he said that he would have someone call me, im assuming monday
to talk about the issue...

OK, so that gives us a bit more to go on.

Based on what you said, I'd say that what Graham ("Eeyore") is
suggesting about the hum originating from the unit's own power supply
is, once again, grasping at straws. That's basically saying that the
unit was designed and built "broken", withe the offending channels
somehow picking up 60 Hz hum from a power transformer or some such.
While that's possible, it's not the first idea that would pop into my
mind (unless, of course, it's made by a company with a history of
producing badly-built junk).


--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
Made With Pears: Pretty good chance that pears will be detectable in
the product.
Contains Pears: One pear seed per multiple tons of product.

(with apologies to Dorothy L. Sayers)

[Eeyore]

Scott Prian wrote:

Eeyore;863081 Wrote:
David Nebenzahl wrote:
-
On 3/21/2009 4:48 AM Eeyore spake thus:-
David Nebenzahl wrote:-
On 3/20/2009 7:49 AM Eeyore spake thus:
Scott Prian wrote:

All of the channels were recognized and sounding alright... at
first,
till I plugged into channels 7 and 8 and I noticed theres an
annoying
60 cycle buzz that doesnt change when i touch the timecode
ins/outs.
The buz is in every channel at higher gains but sticks out in
the last
two channels.

Oddly, the hum is effected by gain knobs but NOT effected by
Pad. So
then i used the inserts in the LT to send the analog signals to
the
2408 and the hum is still there in the same channels.

Any ideas?

Yes, this happens with computer audio. I doubt computer makers
will ever
care much ( one of the main problems is usually in the PSU
actually ). Are
you running ALL your signals properly balanced ? That ought to
fix things.
So don't use an unbalanced input monitor amp etc etc. Why it's
the last 2
channels is anyone's guess but I'll bet there's 'something'
different about
how the source is wired or whatever.

In other words, "I have no ****ing idea, but I'm going to
pontificate
about balanced lines, etc., as is my wont."-

Balancing can make HUGE differences. Has the OP done this ? And
then I thought it
could be PSU placement in the unit. I've heard this effect happen
in other gear.

So I have 2 good leads.-

How in the *world* could unbalanced inputs cause 2 channels to
exhibit
hum and the others to operate normally?-

We don't know what he has connected and how. Since he seems
uninterested in responding
we probably never will.

-
Assuming that all channels are connected identically.-

NEVER 'assume' anything ! That's where most mistakes are made.

-
Sounds like grasping at straws to me.-

You're clueless. I notice you've avoided the PSU placement issue.

Graham

I did mention before about how I had no cables besides the headphones
plugged in, the hum exists more as the channel 'number' increases.

That would tally with a poor internal PSU design placed at the RHS of the
equiupment ( as viewed from the front ). NO question.


By this i mean, there is little hum in 1,2,3,4 but in 5,6 theres it is
enough to be bothersome, and in 7,8 it is too much to be usable.

Exactly.


like I said, it has nothing to do with cables im using because im not
using cables at all

So how does the sound get in and out ?


and it still makes the noise through ADAT out and
the line (tip of insert) out. I notified the salesman about it via
email, he said that he would have someone call me, im assuming monday
to talk about the issue...

I will repost something on any word of the problem.

I look forward to hearing more info.

Graham

[Eeyore]

David Nebenzahl wrote:

On 3/22/2009 12:25 AM Scott Prian spake thus:

I did mention before about how I had no cables besides the headphones
plugged in, the hum exists more as the channel 'number' increases.

By this i mean, there is little hum in 1,2,3,4 but in 5,6 theres it is
enough to be bothersome, and in 7,8 it is too much to be usable.

like I said, it has nothing to do with cables im using because im not
using cables at all and it still makes the noise through ADAT out and
the line (tip of insert) out. I notified the salesman about it via
email, he said that he would have someone call me, im assuming monday
to talk about the issue...

OK, so that gives us a bit more to go on.

Based on what you said, I'd say that what Graham ("Eeyore") is
suggesting about the hum originating from the unit's own power supply
is, once again, grasping at straws.

Oh, it happens. Reducing or removing the effect is far from easy. I once
thought I was having an angina attack over such an issue. It was just
tension thankfully.


That's basically saying that the
unit was designed and built "broken", withe the offending channels
somehow picking up 60 Hz hum from a power transformer or some such.
While that's possible, it's not the first idea that would pop into my
mind (unless, of course, it's made by a company with a history of
producing badly-built junk).

It happens regularly. You see I'm one of the few ( the only ? ) posting in
this group who has a firm grasp on design issues of this sort. They're not
easy to fix but it can be done with resolve.

Graham