Hello o great gurus of audio.

I have a strange problem.

I record live music in the NYC jam scene. I just used a new rig setup
last night, and got the strangest problem.

The show sounded great, but for 15 minutes I got horrible static. I
think it sounds like digital static (as opposed to the mics peaking).
Here is what I know:

1 - There were no changes in house levels throughout the show - this
house only uses the PA for vocals, and the musicians barely touched
their own levels all night.

2 - I do not think it is the mics peaking b/c the static looks the same
on each channel.

3 - Here is the source for the recording: Oktava mk-012s (hyper)
Presonus Firebox (XLR in, phantom power on, getting its power from the
Firewire bus) iBook G4 (Cubase)

4 - The static was audible through the headphone monitor on the firebox

5 - The static begins slowly, and fades away in the same way about 15
minutes later.

Please listen and let me know what you think. You can download a 1
minute sample of the file at:
http://homepage.mac.com/egutin/FileSharing8.html

Thanks a bunch.

On 10 Jul 2005 19:27:57 -0700, "
wrote:

Hello o great gurus of audio.

I have a strange problem.

I record live music in the NYC jam scene. I just used a new rig setup
last night, and got the strangest problem.

The show sounded great, but for 15 minutes I got horrible static. I
think it sounds like digital static (as opposed to the mics peaking).
Here is what I know:

1 - There were no changes in house levels throughout the show - this
house only uses the PA for vocals, and the musicians barely touched
their own levels all night.

2 - I do not think it is the mics peaking b/c the static looks the same
on each channel.

3 - Here is the source for the recording: Oktava mk-012s (hyper)
Presonus Firebox (XLR in, phantom power on, getting its power from the
Firewire bus) iBook G4 (Cubase)

4 - The static was audible through the headphone monitor on the firebox

5 - The static begins slowly, and fades away in the same way about 15
minutes later.

Please listen and let me know what you think. You can download a 1
minute sample of the file at:
http://homepage.mac.com/egutin/FileSharing8.html

I listened and can't tell anything offhand (other than it sounds as
described), then I converted it to .wav and looked at it CE 2000, and
I can see the 'ticks' but I wonder how much of what I see is the REAL
waveform and how much might have been changed by the mp3 encode/decode
process.
It may help more to have an uncompressed .wav file of 5 or 10
seconds of the worst part, so we really 'see' as well as hear the
condition.
The noise/distortion is apparently modulated by the audio,
especially by the bass, whatever that might mean. It's surely not
something clipping or 'peaking' anywhere in the chain.

Thanks a bunch.

-----
http://www.mindspring.com/~benbradley

Addendum - lowering the gain on the channels had no affect, except to
make the static quieter.

" wrote:

Hello o great gurus of audio.

I have a strange problem.

I record live music in the NYC jam scene. I just used a new rig setup
last night, and got the strangest problem.

The show sounded great, but for 15 minutes I got horrible static. I
think it sounds like digital static (as opposed to the mics peaking).
Here is what I know:

1 - There were no changes in house levels throughout the show - this
house only uses the PA for vocals, and the musicians barely touched
their own levels all night.

2 - I do not think it is the mics peaking b/c the static looks the same
on each channel.

3 - Here is the source for the recording: Oktava mk-012s (hyper)
Presonus Firebox (XLR in, phantom power on, getting its power from the
Firewire bus) iBook G4 (Cubase)

4 - The static was audible through the headphone monitor on the firebox

5 - The static begins slowly, and fades away in the same way about 15
minutes later.

Please listen and let me know what you think. You can download a 1
minute sample of the file at:
http://homepage.mac.com/egutin/FileSharing8.html

Digital connection ? Yes.

Sounds like classic sync problems. You don't get this with analogue
! ;-)

Graham

Sounds like classic sync problems. You don't get this with analogue

If that is the case, could sync problems only happen for 15 minutes out
of, say, an hour and a half of audio? With no changes made to settings?

- Eitan

" wrote:

Sounds like classic sync problems. You don't get this with analogue

If that is the case, could sync problems only happen for 15 minutes out
of, say, an hour and a half of audio? With no changes made to settings?

Conceivably - yes. Chances are that some setting was defective. The system
might have finally locked up by default rather than intent.

Without more info it's truly hard to say.


Graham

In article .com,
" wrote:

Hello o great gurus of audio.

I have a strange problem.

I record live music in the NYC jam scene. I just used a new rig setup
last night, and got the strangest problem.

The show sounded great, but for 15 minutes I got horrible static. I
think it sounds like digital static (as opposed to the mics peaking).
Here is what I know:

1 - There were no changes in house levels throughout the show - this
house only uses the PA for vocals, and the musicians barely touched
their own levels all night.

2 - I do not think it is the mics peaking b/c the static looks the same
on each channel.

3 - Here is the source for the recording: Oktava mk-012s (hyper)
Presonus Firebox (XLR in, phantom power on, getting its power from the
Firewire bus) iBook G4 (Cubase)

4 - The static was audible through the headphone monitor on the firebox

5 - The static begins slowly, and fades away in the same way about 15
minutes later.

Please listen and let me know what you think. You can download a 1
minute sample of the file at:
http://homepage.mac.com/egutin/FileSharing8.html

Thanks a bunch.

Zoom in pretty close and you can see the discontinuities in the
waveform. I don't think they're an artifact of the mp3 conversion...it
looks like you're dropping samples in a pretty serious way.

Does the headphone monitor on the Firebox come before or after the
recording application (Cubase)? If you're monitoring after going through
Cubase, than I'd lean towards a software issue.

If you're monitoring pre-Cubase, it's hardware. Your firebox may be
broken! (that didn't come out right....)

Jeff C.

--
Anti-Spam email address in effect.
My real email should be pretty obvious to an actual human being.

wrote in message
oups.com
Hello o great gurus of audio.

I have a strange problem.

I record live music in the NYC jam scene. I just used a
new
rig setup last night, and got the strangest problem.

The show sounded great, but for 15 minutes I got horrible
static. I think it sounds like digital static (as opposed
to
the mics peaking). Here is what I know:

1 - There were no changes in house levels throughout the
show
- this house only uses the PA for vocals, and the
musicians
barely touched their own levels all night.

Sounds like electrical interference from a sparking motor,
or something like it.

On Mon, 11 Jul 2005 07:54:10 -0400, "Arny Krueger"
wrote:

wrote in message
roups.com
Hello o great gurus of audio.

I have a strange problem.

I record live music in the NYC jam scene. I just used a
new
rig setup last night, and got the strangest problem.

The show sounded great, but for 15 minutes I got horrible
static. I think it sounds like digital static (as opposed
to
the mics peaking). Here is what I know:

1 - There were no changes in house levels throughout the
show
- this house only uses the PA for vocals, and the
musicians
barely touched their own levels all night.

Sounds like electrical interference from a sparking motor,
or something like it.


No, this isn't interference. Interference would simply add itself to
the signal. This is clearly multiplying with the signal in some
non-linear fashion a bit like a ring modulator. Assuming this happened
in the digital domain, I would imagine that the computer got very busy
with something else for a while, and didn't have sufficient resources
to devote to the audio.

d

Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote in message

On Mon, 11 Jul 2005 07:54:10 -0400, "Arny Krueger"
wrote:

Sounds like electrical interference from a sparking
motor,
or something like it.

No, this isn't interference.

Really?

Interference would simply add itself to the signal.

Thats what I hear, and that's what I see in detailed
examination of the waves in Audition.

This is clearly multiplying with the
signal in some non-linear fashion a bit like a ring
modulator.

Not clear at all. I see a goodly number of little square
waves of various amplitudes and durations added to the
music. It is true that there is the appearance of some kind
of modulation effect related to the music. See below.

Assuming this happened in the digital domain, I would
imagine
that the computer got very busy with something else for a
while, and didn't have sufficient resources to devote to
the
audio.

I've experienced that many times and it sounds and looks
different. For one thing, a busy computer drops data. I
don't see evidence of data loss. If the noise is being
modulated by the music, that doesn't happen with data loss
in the computer doing the recording. The modulating signal
will be something else, like a hard drive running or video
being displayed.

If I was going to make an alternative diagnosis, it would be
a loose connection of some sort, possibly one that was in
the sound field.

On Mon, 11 Jul 2005 08:54:38 -0400, "Arny Krueger"
wrote:

"Don Pearce" wrote in message

On Mon, 11 Jul 2005 07:54:10 -0400, "Arny Krueger"
wrote:

Sounds like electrical interference from a sparking
motor,
or something like it.

No, this isn't interference.

Really?

Interference would simply add itself to the signal.

Thats what I hear, and that's what I see in detailed
examination of the waves in Audition.

This is clearly multiplying with the
signal in some non-linear fashion a bit like a ring
modulator.

Not clear at all. I see a goodly number of little square
waves of various amplitudes and durations added to the
music. It is true that there is the appearance of some kind
of modulation effect related to the music. See below.

Assuming this happened in the digital domain, I would
imagine
that the computer got very busy with something else for a
while, and didn't have sufficient resources to devote to
the
audio.

I've experienced that many times and it sounds and looks
different. For one thing, a busy computer drops data. I
don't see evidence of data loss. If the noise is being
modulated by the music, that doesn't happen with data loss
in the computer doing the recording. The modulating signal
will be something else, like a hard drive running or video
being displayed.

If I was going to make an alternative diagnosis, it would be
a loose connection of some sort, possibly one that was in
the sound field.


Listen to the part around 38 to 43 seconds, and the multiplication
will be very audible.

d

Pearce Consulting
http://www.pearce.uk.com

wrote:
Addendum - lowering the gain on the channels had no affect, except to
make the static quieter.

Well, now you know that whatever caused the noise is _in front_ of the
channel gain control.

Is it on one channel or both?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Arny Krueger" wrote ...
"Don Pearce" wrote
This is clearly multiplying with the
signal in some non-linear fashion a bit like a ring
modulator.

Not clear at all. I see a goodly number of little square
waves of various amplitudes and durations added to the
music. It is true that there is the appearance of some kind
of modulation effect related to the music. See below.

Have we ever established how faithfully MP3 can reproduce
this kind of aberrent waveform? Otherwise, using MP3 to
do this kind of diagnosis seems questionable at best. I'd
be much more comfortable looking at a few seconds of
real WAV data.

On Mon, 11 Jul 2005 06:13:05 -0700, "Richard Crowley"
wrote:

"Arny Krueger" wrote ...
"Don Pearce" wrote
This is clearly multiplying with the
signal in some non-linear fashion a bit like a ring
modulator.

Not clear at all. I see a goodly number of little square
waves of various amplitudes and durations added to the
music. It is true that there is the appearance of some kind
of modulation effect related to the music. See below.

Have we ever established how faithfully MP3 can reproduce
this kind of aberrent waveform? Otherwise, using MP3 to
do this kind of diagnosis seems questionable at best. I'd
be much more comfortable looking at a few seconds of
real WAV data.

I don't think that MP3 will mess up the waveform to the extent that is
audible here, but in general terms I agree, wav would be better.

d

Pearce Consulting
http://www.pearce.uk.com

I agree the static is definitely multiplicative, the static gets louder
when the music is louder and softer when the music is softer. If the
static were additive, the static would be constant regardless of the
music.

I have heard multiplicative static like that before from defective CDs
that have very large error rates. It is difficult to guess what could
cause that in your system but it is probably NOT external analog
interference like a motor or cell phone.

What could be causing bit errors in your system?

Mark

Don Pearce wrote:

Listen to the part around 38 to 43 seconds, and the multiplication
will be very audible.

Are you sure that's not a weird mp3 artifact?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 11 Jul 2005 09:27:46 -0400, (Scott Dorsey) wrote:

Don Pearce wrote:

Listen to the part around 38 to 43 seconds, and the multiplication
will be very audible.

Are you sure that's not a weird mp3 artifact?
--scott

Obviously not sure, but that would be one hell of an artifact.

d

Pearce Consulting
http://www.pearce.uk.com

Wow - lots of great input. It looks like I have some testing to do, and
some detective work as well. thanks everyone.

- E

ps - the regular spikes are not from the mp3 - they are present in the
original WAV as well.

wrote:
Hello o great gurus of audio.

I have a strange problem.

I record live music in the NYC jam scene. I just used a new rig setup
last night, and got the strangest problem.

The show sounded great, but for 15 minutes I got horrible static. I
think it sounds like digital static (as opposed to the mics peaking).
Here is what I know:

1 - There were no changes in house levels throughout the show - this
house only uses the PA for vocals, and the musicians barely touched
their own levels all night.

2 - I do not think it is the mics peaking b/c the static looks the same
on each channel.

3 - Here is the source for the recording: Oktava mk-012s (hyper)
Presonus Firebox (XLR in, phantom power on, getting its power from the
Firewire bus) iBook G4 (Cubase)

4 - The static was audible through the headphone monitor on the firebox

5 - The static begins slowly, and fades away in the same way about 15
minutes later.

Please listen and let me know what you think. You can download a 1
minute sample of the file at:
http://homepage.mac.com/egutin/FileSharing8.html

Thanks a bunch.

Sounds to me like it might be a power-related problem, i.e. there isn't
enough power. Since the audio, particularly bass sounds seem to
modulate the effect, it sounds like a switching power supply was
struggling somewhere in the signal chain and thus spewing hash all over
the audio.

I've done gigs where the lights dim on each note from the bass... this
is the switching supply/digital audio version of that.

Just my .02

Karl Winkler
Lectrosonics, Inc.
http://www.lectrosonics.com

Sounds like a dirty conection via the desk to your input....I have had
the problem before. Hope this helps.

I'll bring up the power handling issue with the manufacturer - maybe it
really runs best off of external power, and not the firewire bus.

However, steve brought up ice machine - there was one running at the
bar probably 15 feet or so from the mics. If thats the culprit, It
shouldnt come up too often, but I would still need a way to combat it.

Again, thanks everyone.

- E

Pooh Bear wrote:
" wrote:

Sounds like classic sync problems. You don't get this with analogue

If that is the case, could sync problems only happen for 15 minutes out
of, say, an hour and a half of audio? With no changes made to settings?

Conceivably - yes. Chances are that some setting was defective. The system
might have finally locked up by default rather than intent.

Without more info it's truly hard to say.


Graham

It does sound like a sync problem. I've heard artifacts like that when
two devices working with each other are both set to internal clock.

Peter