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P8Z68/GEN3 Deluxe Noisy USB Bus



 
 
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  #1  
Old September 2nd 18, 02:10 AM posted to alt.comp.periphs.mainboard.asus
Tater
external usenet poster
 
Posts: 10
Default P8Z68/GEN3 Deluxe Noisy USB Bus

I was trying to listen to some MP3s on my PC via iTunes, and suddenly
I was like "What the heck - this sounds like crap". I was getting
random clicking and crackling noises. It basically sounded like I was
playing back a badly worn LP.

First I tried the same track several times in a row and confirmed that
the clicks and pops were random - not in the same location in the
track. I tried different tracks from other albums - same story.

Then I turned to hardware troubleshooting - before I tell you about
that let me describe the sound system on my computer:

It's PC to USB DAC to tube preamp to amplified speakers. I am not
using the onboard sound on the motherboard. The USB DAC (digital to
analog converter) is a little gadget like a USB thumb drive that plugs
into a USB port on the back of the PC and outputs an analog signal on
a standard 1/8" phone jack. The tube preamp provides volume control
(and that "good old tube sound"), and the speakers each have their own
amplifiers built in.

First thing I thought was I had a bad connection somewhere. I
unplugged and reseated the DAC and all the analog connections. Didn't
help.

I ruled out a bad speaker because the noise was occurring in both
channels.

Next I pulled out an older DAC and swapped the DACs out. Didn't help.
I moved the DAC to two other USB ports - didn't help.

I moved the DAC to my add-in Inateck USB 3.0 board (I'm not using the
onboard USB 3.0 on this motherboard). This seemed to make the noise
even worse.

To eliminate the tube preamp as a source of noise I disconnected the
preamp and speakers, and plugged a set of headphones directly into the
jack on the DAC. I Still heard the same noises via the headphones.

So now I've isolated the noise all the way back to the PC itself - my
troubleshooting has eliminated anything external to the PC as a
possible source of noise.

I suppose it might be a noisy power supply (and I do have a spare) but
that's a lot of work to change out unless I truly have to.

The only other thing I could think of trying at this point was to
remove the DAC and activate the onboard sound chip on the motherboard,
so that's what I did. Asus had a massive Windows 10 audio driver on
their web site that came out two years ago - but I decided to let
Windows try and install the sound device by itself, figuring I'd
probably get a more up to date driver that way. It did find a driver
for it - it's a pretty basic driver, but I don't need any fancy
features. Pure unadulterated two channel sound is all I was looking
for.

So I hooked up my preamp to the onboard sound port and played an MP3.
Sounds fine, zero noise. I'm not going to say it's as good as the USB
DAC, but it sounds a heck of a lot better than I was expecting.

This leaves questions though. If the power supply was noisy,
shouldn't that noise have permeated the onboard sound system as well?

What is the nature of this noise I'm hearing through the USB DAC? If
there is random noise on my USB bus, I would think I'd be at risk for
corrupted data on USB devices like my big backup drive or my USB thumb
drives?

Any advice is appreciated!

Configuration:

Asus P8Z68 Deluxe/GEN3 motherboard
4x4GB Corsair Vengeance LP DDR3 1600 RAM
Intel i7-2700K CPU
EVGA Supernova 850 T2 power suppy
EVGA GTX 970 FTW+ 4GB video card
SanDisk Extreme Pro 480GB SSD boot drive
2x1TB Western Digital Black data drives
Western Digital 8TB My Book Duo USB backup drive (in Raid 1)
Antec P280 case
Noctua CPU cooler and 3 Noctua case fans
Inateck KTU3FR-2O2I add-in USB 3.0 card
Pioneer 16X Blu-ray burner
Windows 10 Pro version 1803
Meridian Explorer 2 DAC
ifi iTube preamp
Paradigm Shift A2 speakers

Thanks in advance.

Jerry
  #2  
Old September 2nd 18, 04:24 AM posted to alt.comp.periphs.mainboard.asus
Paul[_26_]
external usenet poster
 
Posts: 888
Default P8Z68/GEN3 Deluxe Noisy USB Bus

Tater wrote:
I was trying to listen to some MP3s on my PC via iTunes, and suddenly
I was like "What the heck - this sounds like crap". I was getting
random clicking and crackling noises. It basically sounded like I was
playing back a badly worn LP.

First I tried the same track several times in a row and confirmed that
the clicks and pops were random - not in the same location in the
track. I tried different tracks from other albums - same story.

Then I turned to hardware troubleshooting - before I tell you about
that let me describe the sound system on my computer:

It's PC to USB DAC to tube preamp to amplified speakers. I am not
using the onboard sound on the motherboard. The USB DAC (digital to
analog converter) is a little gadget like a USB thumb drive that plugs
into a USB port on the back of the PC and outputs an analog signal on
a standard 1/8" phone jack. The tube preamp provides volume control
(and that "good old tube sound"), and the speakers each have their own
amplifiers built in.

First thing I thought was I had a bad connection somewhere. I
unplugged and reseated the DAC and all the analog connections. Didn't
help.

I ruled out a bad speaker because the noise was occurring in both
channels.

Next I pulled out an older DAC and swapped the DACs out. Didn't help.
I moved the DAC to two other USB ports - didn't help.

I moved the DAC to my add-in Inateck USB 3.0 board (I'm not using the
onboard USB 3.0 on this motherboard). This seemed to make the noise
even worse.

To eliminate the tube preamp as a source of noise I disconnected the
preamp and speakers, and plugged a set of headphones directly into the
jack on the DAC. I Still heard the same noises via the headphones.

So now I've isolated the noise all the way back to the PC itself - my
troubleshooting has eliminated anything external to the PC as a
possible source of noise.

I suppose it might be a noisy power supply (and I do have a spare) but
that's a lot of work to change out unless I truly have to.

The only other thing I could think of trying at this point was to
remove the DAC and activate the onboard sound chip on the motherboard,
so that's what I did. Asus had a massive Windows 10 audio driver on
their web site that came out two years ago - but I decided to let
Windows try and install the sound device by itself, figuring I'd
probably get a more up to date driver that way. It did find a driver
for it - it's a pretty basic driver, but I don't need any fancy
features. Pure unadulterated two channel sound is all I was looking
for.

So I hooked up my preamp to the onboard sound port and played an MP3.
Sounds fine, zero noise. I'm not going to say it's as good as the USB
DAC, but it sounds a heck of a lot better than I was expecting.

This leaves questions though. If the power supply was noisy,
shouldn't that noise have permeated the onboard sound system as well?

What is the nature of this noise I'm hearing through the USB DAC? If
there is random noise on my USB bus, I would think I'd be at risk for
corrupted data on USB devices like my big backup drive or my USB thumb
drives?

Any advice is appreciated!

Configuration:

Asus P8Z68 Deluxe/GEN3 motherboard
4x4GB Corsair Vengeance LP DDR3 1600 RAM
Intel i7-2700K CPU
EVGA Supernova 850 T2 power suppy
EVGA GTX 970 FTW+ 4GB video card
SanDisk Extreme Pro 480GB SSD boot drive
2x1TB Western Digital Black data drives
Western Digital 8TB My Book Duo USB backup drive (in Raid 1)
Antec P280 case
Noctua CPU cooler and 3 Noctua case fans
Inateck KTU3FR-2O2I add-in USB 3.0 card
Pioneer 16X Blu-ray burner
Windows 10 Pro version 1803
Meridian Explorer 2 DAC
ifi iTube preamp
Paradigm Shift A2 speakers

Thanks in advance.

Jerry


It sounds like you already have good debugging skills,
so I won't need to add much.

You can record the output of your DAC, using the
onboard sound and the LineIn on it. That's one
possibility.

Using Audacity, you could record the output waveform,
and compare it to your stimulus, and see how the noise
modulates the waveform.

Audacity doesn't support playback and recording at
the same time. Which usually means I need two programs,
one to playback a stimulus and a second program
to record, to get the data I want.

Sometimes clicks or pops, are actually flat spots
caused on the output waveform, by "buffer runs dry".
The hardware has to signal that the buffer is getting
low, and the system coughs up a few packets of
data to fill up some kind of queue. If the queue ever
runs dry (because the buffer cannot be serviced in
time), the last voltage level on the DAC "sits there"
until a packet of new samples arrive. The flat spot
makes an audible noise, although not as loud a sound
as you would think.

When digital samples are corrupted (like the MSBit changes
state), that creates a huge pop. And you'd notice that.

So while it's fun to pretend the source is analog, what
you could be hearing is a "delivery system problem".
If you play a sine wave on some LineOut, and then record
on a LineIn, you may notice disturbances which are not
part of a sine wave. And that will give you some idea
what class of fault this is.

*******

The onboard sound has a positive voltage for the
digital portion of the chip. It also has a positive
voltage for the analog portion. That analog power
source, is a relatively small three terminal regulator.
By using a separate regulated power source, the
intention is to reduce the level of "digital noise"
riding on the motherboard sound power rails. Or on
any analog amp after that point.

It's possible to get inductive coupling into
the onboard sound. That happens when the NIC wires
go too close to the LineOut wires. But that would
not be a likely mechanism for an external USB DAC.
And your motherboard sound is clean.

So at this point, I recommend recording the defective
output, so you can diagnose the fault type.

*******

People who buy "audio workstation" motherboards, they
usually run "DPCLat" or delay procedure call latency
test. But it doesn't work on Windows 10.

The time it takes to service a "delayed procedure call",
is a function of the motherboard performance. If the
BIOS uses the SMM (system management mode) interrupt
mechanism, it usurps the OS completely. A USB DAC might
be waiting for a millisecond for data, until the SMM
routine exits and the OS is running again. When this
happens, it ruins the motherboard with respect to running
audio workstation functions.

If you can find a replacement program for "DPCLat",
one that works on Windows 10, you can check out
your "responsiveness" and see whether real-time
performance is compromised for some reason.

When SMM fires off, the OS doesn't know what happened.
All it could notice, is a high performance clock could
be off by a millisecond. The OS has no other record that
it's been swapped out. Programs like DPCLat, attempt
to quantify this problem, by "indirect measurement".
If the DPC Latency has spikes in it, that's generally
a sign that SMM is active. (It's because we don't know
of any other high-enough-priority activity that can
do that to the OS. Intel made sure that SMM was king.)

Note that there is one hardware event, which is
absolutely huge. When your video card changes
into 3D gaming mode, there is a 15 millisecond
spike in the DPCLat trace. Which implies the
video card driver is "stuck" and holding the
kernel hostage for a frame time, while it
switches modes. Normally, people doing audio
workstation work, aren't screwing with 3D games
in the middle of recording their rock group.
So this isn't a problem. I've not done
extensive testing of what happens to tunes,
when the video card changes modes, so I don't
know what that one sounds like.

Paul
  #3  
Old September 2nd 18, 08:33 AM posted to alt.comp.periphs.mainboard.asus
Tater
external usenet poster
 
Posts: 10
Default P8Z68/GEN3 Deluxe Noisy USB Bus

On Sat, 01 Sep 2018 23:24:49 -0400, Paul
wrote:

Tater wrote:
I was trying to listen to some MP3s on my PC via iTunes, and suddenly
I was like "What the heck - this sounds like crap". I was getting
random clicking and crackling noises. It basically sounded like I was
playing back a badly worn LP.

First I tried the same track several times in a row and confirmed that
the clicks and pops were random - not in the same location in the
track. I tried different tracks from other albums - same story.

Then I turned to hardware troubleshooting - before I tell you about
that let me describe the sound system on my computer:

It's PC to USB DAC to tube preamp to amplified speakers. I am not
using the onboard sound on the motherboard. The USB DAC (digital to
analog converter) is a little gadget like a USB thumb drive that plugs
into a USB port on the back of the PC and outputs an analog signal on
a standard 1/8" phone jack. The tube preamp provides volume control
(and that "good old tube sound"), and the speakers each have their own
amplifiers built in.

First thing I thought was I had a bad connection somewhere. I
unplugged and reseated the DAC and all the analog connections. Didn't
help.

I ruled out a bad speaker because the noise was occurring in both
channels.

Next I pulled out an older DAC and swapped the DACs out. Didn't help.
I moved the DAC to two other USB ports - didn't help.

I moved the DAC to my add-in Inateck USB 3.0 board (I'm not using the
onboard USB 3.0 on this motherboard). This seemed to make the noise
even worse.

To eliminate the tube preamp as a source of noise I disconnected the
preamp and speakers, and plugged a set of headphones directly into the
jack on the DAC. I Still heard the same noises via the headphones.

So now I've isolated the noise all the way back to the PC itself - my
troubleshooting has eliminated anything external to the PC as a
possible source of noise.

I suppose it might be a noisy power supply (and I do have a spare) but
that's a lot of work to change out unless I truly have to.

The only other thing I could think of trying at this point was to
remove the DAC and activate the onboard sound chip on the motherboard,
so that's what I did. Asus had a massive Windows 10 audio driver on
their web site that came out two years ago - but I decided to let
Windows try and install the sound device by itself, figuring I'd
probably get a more up to date driver that way. It did find a driver
for it - it's a pretty basic driver, but I don't need any fancy
features. Pure unadulterated two channel sound is all I was looking
for.

So I hooked up my preamp to the onboard sound port and played an MP3.
Sounds fine, zero noise. I'm not going to say it's as good as the USB
DAC, but it sounds a heck of a lot better than I was expecting.

This leaves questions though. If the power supply was noisy,
shouldn't that noise have permeated the onboard sound system as well?

What is the nature of this noise I'm hearing through the USB DAC? If
there is random noise on my USB bus, I would think I'd be at risk for
corrupted data on USB devices like my big backup drive or my USB thumb
drives?

Any advice is appreciated!

Configuration:

Asus P8Z68 Deluxe/GEN3 motherboard
4x4GB Corsair Vengeance LP DDR3 1600 RAM
Intel i7-2700K CPU
EVGA Supernova 850 T2 power suppy
EVGA GTX 970 FTW+ 4GB video card
SanDisk Extreme Pro 480GB SSD boot drive
2x1TB Western Digital Black data drives
Western Digital 8TB My Book Duo USB backup drive (in Raid 1)
Antec P280 case
Noctua CPU cooler and 3 Noctua case fans
Inateck KTU3FR-2O2I add-in USB 3.0 card
Pioneer 16X Blu-ray burner
Windows 10 Pro version 1803
Meridian Explorer 2 DAC
ifi iTube preamp
Paradigm Shift A2 speakers

Thanks in advance.

Jerry


It sounds like you already have good debugging skills,
so I won't need to add much.

You can record the output of your DAC, using the
onboard sound and the LineIn on it. That's one
possibility.

Using Audacity, you could record the output waveform,
and compare it to your stimulus, and see how the noise
modulates the waveform.

Audacity doesn't support playback and recording at
the same time. Which usually means I need two programs,
one to playback a stimulus and a second program
to record, to get the data I want.

Sometimes clicks or pops, are actually flat spots
caused on the output waveform, by "buffer runs dry".
The hardware has to signal that the buffer is getting
low, and the system coughs up a few packets of
data to fill up some kind of queue. If the queue ever
runs dry (because the buffer cannot be serviced in
time), the last voltage level on the DAC "sits there"
until a packet of new samples arrive. The flat spot
makes an audible noise, although not as loud a sound
as you would think.

When digital samples are corrupted (like the MSBit changes
state), that creates a huge pop. And you'd notice that.

So while it's fun to pretend the source is analog, what
you could be hearing is a "delivery system problem".
If you play a sine wave on some LineOut, and then record
on a LineIn, you may notice disturbances which are not
part of a sine wave. And that will give you some idea
what class of fault this is.

*******

The onboard sound has a positive voltage for the
digital portion of the chip. It also has a positive
voltage for the analog portion. That analog power
source, is a relatively small three terminal regulator.
By using a separate regulated power source, the
intention is to reduce the level of "digital noise"
riding on the motherboard sound power rails. Or on
any analog amp after that point.

It's possible to get inductive coupling into
the onboard sound. That happens when the NIC wires
go too close to the LineOut wires. But that would
not be a likely mechanism for an external USB DAC.
And your motherboard sound is clean.

So at this point, I recommend recording the defective
output, so you can diagnose the fault type.

*******

People who buy "audio workstation" motherboards, they
usually run "DPCLat" or delay procedure call latency
test. But it doesn't work on Windows 10.

The time it takes to service a "delayed procedure call",
is a function of the motherboard performance. If the
BIOS uses the SMM (system management mode) interrupt
mechanism, it usurps the OS completely. A USB DAC might
be waiting for a millisecond for data, until the SMM
routine exits and the OS is running again. When this
happens, it ruins the motherboard with respect to running
audio workstation functions.

If you can find a replacement program for "DPCLat",
one that works on Windows 10, you can check out
your "responsiveness" and see whether real-time
performance is compromised for some reason.

When SMM fires off, the OS doesn't know what happened.
All it could notice, is a high performance clock could
be off by a millisecond. The OS has no other record that
it's been swapped out. Programs like DPCLat, attempt
to quantify this problem, by "indirect measurement".
If the DPC Latency has spikes in it, that's generally
a sign that SMM is active. (It's because we don't know
of any other high-enough-priority activity that can
do that to the OS. Intel made sure that SMM was king.)

Note that there is one hardware event, which is
absolutely huge. When your video card changes
into 3D gaming mode, there is a 15 millisecond
spike in the DPCLat trace. Which implies the
video card driver is "stuck" and holding the
kernel hostage for a frame time, while it
switches modes. Normally, people doing audio
workstation work, aren't screwing with 3D games
in the middle of recording their rock group.
So this isn't a problem. I've not done
extensive testing of what happens to tunes,
when the video card changes modes, so I don't
know what that one sounds like.

Paul


Paul,

Thanks for the incredibly thoughtful and highly technical response.

One possibly important clue I forgot to mention earlier is that there
is no noise coming through the DAC when there is no signal. That in
itself might mean that it's not the USB bus itself that's noisy, but
that the noise is being generated by the SATA controller when the MP3
file is being fetched for playback.

I'm goiong to try other sources as a means of troubleshooting this. If
it is the SATA bus, then I should also get the noise when playing back
a CD (because the SATA controller is fetching the WAV file from the CD
drive). However I would not expect to get the noise when playing
Pandora, as that is purely network traffic and doesn't involve the
SATA bus.

I'll do further troubleshooting and report back on Sunday.

Jerry

  #4  
Old September 2nd 18, 11:41 PM posted to alt.comp.periphs.mainboard.asus
Tater
external usenet poster
 
Posts: 10
Default P8Z68/GEN3 Deluxe Noisy USB Bus

On Sun, 02 Sep 2018 00:33:43 -0700, Tater wrote:

On Sat, 01 Sep 2018 23:24:49 -0400, Paul
wrote:

Tater wrote:
I was trying to listen to some MP3s on my PC via iTunes, and suddenly
I was like "What the heck - this sounds like crap". I was getting
random clicking and crackling noises. It basically sounded like I was
playing back a badly worn LP.

First I tried the same track several times in a row and confirmed that
the clicks and pops were random - not in the same location in the
track. I tried different tracks from other albums - same story.

Then I turned to hardware troubleshooting - before I tell you about
that let me describe the sound system on my computer:

It's PC to USB DAC to tube preamp to amplified speakers. I am not
using the onboard sound on the motherboard. The USB DAC (digital to
analog converter) is a little gadget like a USB thumb drive that plugs
into a USB port on the back of the PC and outputs an analog signal on
a standard 1/8" phone jack. The tube preamp provides volume control
(and that "good old tube sound"), and the speakers each have their own
amplifiers built in.

First thing I thought was I had a bad connection somewhere. I
unplugged and reseated the DAC and all the analog connections. Didn't
help.

I ruled out a bad speaker because the noise was occurring in both
channels.

Next I pulled out an older DAC and swapped the DACs out. Didn't help.
I moved the DAC to two other USB ports - didn't help.

I moved the DAC to my add-in Inateck USB 3.0 board (I'm not using the
onboard USB 3.0 on this motherboard). This seemed to make the noise
even worse.

To eliminate the tube preamp as a source of noise I disconnected the
preamp and speakers, and plugged a set of headphones directly into the
jack on the DAC. I Still heard the same noises via the headphones.

So now I've isolated the noise all the way back to the PC itself - my
troubleshooting has eliminated anything external to the PC as a
possible source of noise.

I suppose it might be a noisy power supply (and I do have a spare) but
that's a lot of work to change out unless I truly have to.

The only other thing I could think of trying at this point was to
remove the DAC and activate the onboard sound chip on the motherboard,
so that's what I did. Asus had a massive Windows 10 audio driver on
their web site that came out two years ago - but I decided to let
Windows try and install the sound device by itself, figuring I'd
probably get a more up to date driver that way. It did find a driver
for it - it's a pretty basic driver, but I don't need any fancy
features. Pure unadulterated two channel sound is all I was looking
for.

So I hooked up my preamp to the onboard sound port and played an MP3.
Sounds fine, zero noise. I'm not going to say it's as good as the USB
DAC, but it sounds a heck of a lot better than I was expecting.

This leaves questions though. If the power supply was noisy,
shouldn't that noise have permeated the onboard sound system as well?

What is the nature of this noise I'm hearing through the USB DAC? If
there is random noise on my USB bus, I would think I'd be at risk for
corrupted data on USB devices like my big backup drive or my USB thumb
drives?

Any advice is appreciated!

Configuration:

Asus P8Z68 Deluxe/GEN3 motherboard
4x4GB Corsair Vengeance LP DDR3 1600 RAM
Intel i7-2700K CPU
EVGA Supernova 850 T2 power suppy
EVGA GTX 970 FTW+ 4GB video card
SanDisk Extreme Pro 480GB SSD boot drive
2x1TB Western Digital Black data drives
Western Digital 8TB My Book Duo USB backup drive (in Raid 1)
Antec P280 case
Noctua CPU cooler and 3 Noctua case fans
Inateck KTU3FR-2O2I add-in USB 3.0 card
Pioneer 16X Blu-ray burner
Windows 10 Pro version 1803
Meridian Explorer 2 DAC
ifi iTube preamp
Paradigm Shift A2 speakers

Thanks in advance.

Jerry


It sounds like you already have good debugging skills,
so I won't need to add much.

You can record the output of your DAC, using the
onboard sound and the LineIn on it. That's one
possibility.

Using Audacity, you could record the output waveform,
and compare it to your stimulus, and see how the noise
modulates the waveform.

Audacity doesn't support playback and recording at
the same time. Which usually means I need two programs,
one to playback a stimulus and a second program
to record, to get the data I want.

Sometimes clicks or pops, are actually flat spots
caused on the output waveform, by "buffer runs dry".
The hardware has to signal that the buffer is getting
low, and the system coughs up a few packets of
data to fill up some kind of queue. If the queue ever
runs dry (because the buffer cannot be serviced in
time), the last voltage level on the DAC "sits there"
until a packet of new samples arrive. The flat spot
makes an audible noise, although not as loud a sound
as you would think.

When digital samples are corrupted (like the MSBit changes
state), that creates a huge pop. And you'd notice that.

So while it's fun to pretend the source is analog, what
you could be hearing is a "delivery system problem".
If you play a sine wave on some LineOut, and then record
on a LineIn, you may notice disturbances which are not
part of a sine wave. And that will give you some idea
what class of fault this is.

*******

The onboard sound has a positive voltage for the
digital portion of the chip. It also has a positive
voltage for the analog portion. That analog power
source, is a relatively small three terminal regulator.
By using a separate regulated power source, the
intention is to reduce the level of "digital noise"
riding on the motherboard sound power rails. Or on
any analog amp after that point.

It's possible to get inductive coupling into
the onboard sound. That happens when the NIC wires
go too close to the LineOut wires. But that would
not be a likely mechanism for an external USB DAC.
And your motherboard sound is clean.

So at this point, I recommend recording the defective
output, so you can diagnose the fault type.

*******

People who buy "audio workstation" motherboards, they
usually run "DPCLat" or delay procedure call latency
test. But it doesn't work on Windows 10.

The time it takes to service a "delayed procedure call",
is a function of the motherboard performance. If the
BIOS uses the SMM (system management mode) interrupt
mechanism, it usurps the OS completely. A USB DAC might
be waiting for a millisecond for data, until the SMM
routine exits and the OS is running again. When this
happens, it ruins the motherboard with respect to running
audio workstation functions.

If you can find a replacement program for "DPCLat",
one that works on Windows 10, you can check out
your "responsiveness" and see whether real-time
performance is compromised for some reason.

When SMM fires off, the OS doesn't know what happened.
All it could notice, is a high performance clock could
be off by a millisecond. The OS has no other record that
it's been swapped out. Programs like DPCLat, attempt
to quantify this problem, by "indirect measurement".
If the DPC Latency has spikes in it, that's generally
a sign that SMM is active. (It's because we don't know
of any other high-enough-priority activity that can
do that to the OS. Intel made sure that SMM was king.)

Note that there is one hardware event, which is
absolutely huge. When your video card changes
into 3D gaming mode, there is a 15 millisecond
spike in the DPCLat trace. Which implies the
video card driver is "stuck" and holding the
kernel hostage for a frame time, while it
switches modes. Normally, people doing audio
workstation work, aren't screwing with 3D games
in the middle of recording their rock group.
So this isn't a problem. I've not done
extensive testing of what happens to tunes,
when the video card changes modes, so I don't
know what that one sounds like.

Paul


Paul,

Thanks for the incredibly thoughtful and highly technical response.

One possibly important clue I forgot to mention earlier is that there
is no noise coming through the DAC when there is no signal. That in
itself might mean that it's not the USB bus itself that's noisy, but
that the noise is being generated by the SATA controller when the MP3
file is being fetched for playback.

I'm goiong to try other sources as a means of troubleshooting this. If
it is the SATA bus, then I should also get the noise when playing back
a CD (because the SATA controller is fetching the WAV file from the CD
drive). However I would not expect to get the noise when playing
Pandora, as that is purely network traffic and doesn't involve the
SATA bus.

I'll do further troubleshooting and report back on Sunday.

Jerry


I hate computers! I just now got around to messing with the PC again.
I uninstalled the onboard sound via Device Manager, then rebooted and
entered the BIOS to turn it off. I then re-attached my Meridian
Explorer 2 USB DAC and installed the driver for it (even though the
manufacturer claims it works under Windows 10 without drivers, I've
never been able to make that work - I always have to load the Windows
7 driver).

I checked Device Manager, and the Device Properties dialogs in the
Sound section of Settings to make sure everything was looking normal
and set up correctly. Then I figured I'd better confirm the noise
again before trying different things to troubleshoot it. And
naturally, the noise is now GONE.

I want to pound my head against the wall. All that troubleshooting
yesterday was a waste of time. I never did find the cause of the
problem, and I have no idea why it went away.

Guess I won't be buying a new PC after all.

Paul, thank you again for taking the time to provide all that
wonderful advice for me. I really appreciate it. I'm sorry that it
proved unnecessary in the end.

Jerry
  #5  
Old September 3rd 18, 02:19 AM posted to alt.comp.periphs.mainboard.asus
Paul[_26_]
external usenet poster
 
Posts: 888
Default P8Z68/GEN3 Deluxe Noisy USB Bus

Tater wrote:
On Sun, 02 Sep 2018 00:33:43 -0700, Tater wrote:

On Sat, 01 Sep 2018 23:24:49 -0400, Paul
wrote:

Tater wrote:
I was trying to listen to some MP3s on my PC via iTunes, and suddenly
I was like "What the heck - this sounds like crap". I was getting
random clicking and crackling noises. It basically sounded like I was
playing back a badly worn LP.

First I tried the same track several times in a row and confirmed that
the clicks and pops were random - not in the same location in the
track. I tried different tracks from other albums - same story.

Then I turned to hardware troubleshooting - before I tell you about
that let me describe the sound system on my computer:

It's PC to USB DAC to tube preamp to amplified speakers. I am not
using the onboard sound on the motherboard. The USB DAC (digital to
analog converter) is a little gadget like a USB thumb drive that plugs
into a USB port on the back of the PC and outputs an analog signal on
a standard 1/8" phone jack. The tube preamp provides volume control
(and that "good old tube sound"), and the speakers each have their own
amplifiers built in.

First thing I thought was I had a bad connection somewhere. I
unplugged and reseated the DAC and all the analog connections. Didn't
help.

I ruled out a bad speaker because the noise was occurring in both
channels.

Next I pulled out an older DAC and swapped the DACs out. Didn't help.
I moved the DAC to two other USB ports - didn't help.

I moved the DAC to my add-in Inateck USB 3.0 board (I'm not using the
onboard USB 3.0 on this motherboard). This seemed to make the noise
even worse.

To eliminate the tube preamp as a source of noise I disconnected the
preamp and speakers, and plugged a set of headphones directly into the
jack on the DAC. I Still heard the same noises via the headphones.

So now I've isolated the noise all the way back to the PC itself - my
troubleshooting has eliminated anything external to the PC as a
possible source of noise.

I suppose it might be a noisy power supply (and I do have a spare) but
that's a lot of work to change out unless I truly have to.

The only other thing I could think of trying at this point was to
remove the DAC and activate the onboard sound chip on the motherboard,
so that's what I did. Asus had a massive Windows 10 audio driver on
their web site that came out two years ago - but I decided to let
Windows try and install the sound device by itself, figuring I'd
probably get a more up to date driver that way. It did find a driver
for it - it's a pretty basic driver, but I don't need any fancy
features. Pure unadulterated two channel sound is all I was looking
for.

So I hooked up my preamp to the onboard sound port and played an MP3.
Sounds fine, zero noise. I'm not going to say it's as good as the USB
DAC, but it sounds a heck of a lot better than I was expecting.

This leaves questions though. If the power supply was noisy,
shouldn't that noise have permeated the onboard sound system as well?

What is the nature of this noise I'm hearing through the USB DAC? If
there is random noise on my USB bus, I would think I'd be at risk for
corrupted data on USB devices like my big backup drive or my USB thumb
drives?

Any advice is appreciated!

Configuration:

Asus P8Z68 Deluxe/GEN3 motherboard
4x4GB Corsair Vengeance LP DDR3 1600 RAM
Intel i7-2700K CPU
EVGA Supernova 850 T2 power suppy
EVGA GTX 970 FTW+ 4GB video card
SanDisk Extreme Pro 480GB SSD boot drive
2x1TB Western Digital Black data drives
Western Digital 8TB My Book Duo USB backup drive (in Raid 1)
Antec P280 case
Noctua CPU cooler and 3 Noctua case fans
Inateck KTU3FR-2O2I add-in USB 3.0 card
Pioneer 16X Blu-ray burner
Windows 10 Pro version 1803
Meridian Explorer 2 DAC
ifi iTube preamp
Paradigm Shift A2 speakers

Thanks in advance.

Jerry
It sounds like you already have good debugging skills,
so I won't need to add much.

You can record the output of your DAC, using the
onboard sound and the LineIn on it. That's one
possibility.

Using Audacity, you could record the output waveform,
and compare it to your stimulus, and see how the noise
modulates the waveform.

Audacity doesn't support playback and recording at
the same time. Which usually means I need two programs,
one to playback a stimulus and a second program
to record, to get the data I want.

Sometimes clicks or pops, are actually flat spots
caused on the output waveform, by "buffer runs dry".
The hardware has to signal that the buffer is getting
low, and the system coughs up a few packets of
data to fill up some kind of queue. If the queue ever
runs dry (because the buffer cannot be serviced in
time), the last voltage level on the DAC "sits there"
until a packet of new samples arrive. The flat spot
makes an audible noise, although not as loud a sound
as you would think.

When digital samples are corrupted (like the MSBit changes
state), that creates a huge pop. And you'd notice that.

So while it's fun to pretend the source is analog, what
you could be hearing is a "delivery system problem".
If you play a sine wave on some LineOut, and then record
on a LineIn, you may notice disturbances which are not
part of a sine wave. And that will give you some idea
what class of fault this is.

*******

The onboard sound has a positive voltage for the
digital portion of the chip. It also has a positive
voltage for the analog portion. That analog power
source, is a relatively small three terminal regulator.
By using a separate regulated power source, the
intention is to reduce the level of "digital noise"
riding on the motherboard sound power rails. Or on
any analog amp after that point.

It's possible to get inductive coupling into
the onboard sound. That happens when the NIC wires
go too close to the LineOut wires. But that would
not be a likely mechanism for an external USB DAC.
And your motherboard sound is clean.

So at this point, I recommend recording the defective
output, so you can diagnose the fault type.

*******

People who buy "audio workstation" motherboards, they
usually run "DPCLat" or delay procedure call latency
test. But it doesn't work on Windows 10.

The time it takes to service a "delayed procedure call",
is a function of the motherboard performance. If the
BIOS uses the SMM (system management mode) interrupt
mechanism, it usurps the OS completely. A USB DAC might
be waiting for a millisecond for data, until the SMM
routine exits and the OS is running again. When this
happens, it ruins the motherboard with respect to running
audio workstation functions.

If you can find a replacement program for "DPCLat",
one that works on Windows 10, you can check out
your "responsiveness" and see whether real-time
performance is compromised for some reason.

When SMM fires off, the OS doesn't know what happened.
All it could notice, is a high performance clock could
be off by a millisecond. The OS has no other record that
it's been swapped out. Programs like DPCLat, attempt
to quantify this problem, by "indirect measurement".
If the DPC Latency has spikes in it, that's generally
a sign that SMM is active. (It's because we don't know
of any other high-enough-priority activity that can
do that to the OS. Intel made sure that SMM was king.)

Note that there is one hardware event, which is
absolutely huge. When your video card changes
into 3D gaming mode, there is a 15 millisecond
spike in the DPCLat trace. Which implies the
video card driver is "stuck" and holding the
kernel hostage for a frame time, while it
switches modes. Normally, people doing audio
workstation work, aren't screwing with 3D games
in the middle of recording their rock group.
So this isn't a problem. I've not done
extensive testing of what happens to tunes,
when the video card changes modes, so I don't
know what that one sounds like.

Paul

Paul,

Thanks for the incredibly thoughtful and highly technical response.

One possibly important clue I forgot to mention earlier is that there
is no noise coming through the DAC when there is no signal. That in
itself might mean that it's not the USB bus itself that's noisy, but
that the noise is being generated by the SATA controller when the MP3
file is being fetched for playback.

I'm goiong to try other sources as a means of troubleshooting this. If
it is the SATA bus, then I should also get the noise when playing back
a CD (because the SATA controller is fetching the WAV file from the CD
drive). However I would not expect to get the noise when playing
Pandora, as that is purely network traffic and doesn't involve the
SATA bus.

I'll do further troubleshooting and report back on Sunday.

Jerry


I hate computers! I just now got around to messing with the PC again.
I uninstalled the onboard sound via Device Manager, then rebooted and
entered the BIOS to turn it off. I then re-attached my Meridian
Explorer 2 USB DAC and installed the driver for it (even though the
manufacturer claims it works under Windows 10 without drivers, I've
never been able to make that work - I always have to load the Windows
7 driver).

I checked Device Manager, and the Device Properties dialogs in the
Sound section of Settings to make sure everything was looking normal
and set up correctly. Then I figured I'd better confirm the noise
again before trying different things to troubleshoot it. And
naturally, the noise is now GONE.

I want to pound my head against the wall. All that troubleshooting
yesterday was a waste of time. I never did find the cause of the
problem, and I have no idea why it went away.

Guess I won't be buying a new PC after all.

Paul, thank you again for taking the time to provide all that
wonderful advice for me. I really appreciate it. I'm sorry that it
proved unnecessary in the end.

Jerry


So what you discovered was, the noise was indeed temporal
servicing noise, not analog noise, because now the DAC is clear.

And in future, you can test for "responsiveness" on the PC,
as a root cause.

Normally, this should never be a problem. The hardware
interrupts from USB, should be serviced right away.

1) Stub service routine responds practically instantly.
This is the driver in Ring0, down where the kernel lives.
2) Extended service (filling buffer for next time, preparing
DMA chain or whatever), that service request is queued
on the DPC queue. Delay procedure calls run in Ring3,
like they were an application.
3) The OS monitors the DPC queue, and if the OS is falling
behind, it's supposed to have an internal setting where
more of the cores work on reducing the depth of the DPC
queue.

If all of that crap keeps your sound buffer full, there
won't be any of "that kind" of noise.

Paul
  #6  
Old September 3rd 18, 08:57 PM posted to alt.comp.periphs.mainboard.asus
Tater
external usenet poster
 
Posts: 10
Default P8Z68/GEN3 Deluxe Noisy USB Bus

On Sun, 02 Sep 2018 21:19:35 -0400, Paul
wrote:

Tater wrote:
On Sun, 02 Sep 2018 00:33:43 -0700, Tater wrote:

On Sat, 01 Sep 2018 23:24:49 -0400, Paul
wrote:

Tater wrote:
I was trying to listen to some MP3s on my PC via iTunes, and suddenly
I was like "What the heck - this sounds like crap". I was getting
random clicking and crackling noises. It basically sounded like I was
playing back a badly worn LP.

First I tried the same track several times in a row and confirmed that
the clicks and pops were random - not in the same location in the
track. I tried different tracks from other albums - same story.

Then I turned to hardware troubleshooting - before I tell you about
that let me describe the sound system on my computer:

It's PC to USB DAC to tube preamp to amplified speakers. I am not
using the onboard sound on the motherboard. The USB DAC (digital to
analog converter) is a little gadget like a USB thumb drive that plugs
into a USB port on the back of the PC and outputs an analog signal on
a standard 1/8" phone jack. The tube preamp provides volume control
(and that "good old tube sound"), and the speakers each have their own
amplifiers built in.

First thing I thought was I had a bad connection somewhere. I
unplugged and reseated the DAC and all the analog connections. Didn't
help.

I ruled out a bad speaker because the noise was occurring in both
channels.

Next I pulled out an older DAC and swapped the DACs out. Didn't help.
I moved the DAC to two other USB ports - didn't help.

I moved the DAC to my add-in Inateck USB 3.0 board (I'm not using the
onboard USB 3.0 on this motherboard). This seemed to make the noise
even worse.

To eliminate the tube preamp as a source of noise I disconnected the
preamp and speakers, and plugged a set of headphones directly into the
jack on the DAC. I Still heard the same noises via the headphones.

So now I've isolated the noise all the way back to the PC itself - my
troubleshooting has eliminated anything external to the PC as a
possible source of noise.

I suppose it might be a noisy power supply (and I do have a spare) but
that's a lot of work to change out unless I truly have to.

The only other thing I could think of trying at this point was to
remove the DAC and activate the onboard sound chip on the motherboard,
so that's what I did. Asus had a massive Windows 10 audio driver on
their web site that came out two years ago - but I decided to let
Windows try and install the sound device by itself, figuring I'd
probably get a more up to date driver that way. It did find a driver
for it - it's a pretty basic driver, but I don't need any fancy
features. Pure unadulterated two channel sound is all I was looking
for.

So I hooked up my preamp to the onboard sound port and played an MP3.
Sounds fine, zero noise. I'm not going to say it's as good as the USB
DAC, but it sounds a heck of a lot better than I was expecting.

This leaves questions though. If the power supply was noisy,
shouldn't that noise have permeated the onboard sound system as well?

What is the nature of this noise I'm hearing through the USB DAC? If
there is random noise on my USB bus, I would think I'd be at risk for
corrupted data on USB devices like my big backup drive or my USB thumb
drives?

Any advice is appreciated!

Configuration:

Asus P8Z68 Deluxe/GEN3 motherboard
4x4GB Corsair Vengeance LP DDR3 1600 RAM
Intel i7-2700K CPU
EVGA Supernova 850 T2 power suppy
EVGA GTX 970 FTW+ 4GB video card
SanDisk Extreme Pro 480GB SSD boot drive
2x1TB Western Digital Black data drives
Western Digital 8TB My Book Duo USB backup drive (in Raid 1)
Antec P280 case
Noctua CPU cooler and 3 Noctua case fans
Inateck KTU3FR-2O2I add-in USB 3.0 card
Pioneer 16X Blu-ray burner
Windows 10 Pro version 1803
Meridian Explorer 2 DAC
ifi iTube preamp
Paradigm Shift A2 speakers

Thanks in advance.

Jerry
It sounds like you already have good debugging skills,
so I won't need to add much.

You can record the output of your DAC, using the
onboard sound and the LineIn on it. That's one
possibility.

Using Audacity, you could record the output waveform,
and compare it to your stimulus, and see how the noise
modulates the waveform.

Audacity doesn't support playback and recording at
the same time. Which usually means I need two programs,
one to playback a stimulus and a second program
to record, to get the data I want.

Sometimes clicks or pops, are actually flat spots
caused on the output waveform, by "buffer runs dry".
The hardware has to signal that the buffer is getting
low, and the system coughs up a few packets of
data to fill up some kind of queue. If the queue ever
runs dry (because the buffer cannot be serviced in
time), the last voltage level on the DAC "sits there"
until a packet of new samples arrive. The flat spot
makes an audible noise, although not as loud a sound
as you would think.

When digital samples are corrupted (like the MSBit changes
state), that creates a huge pop. And you'd notice that.

So while it's fun to pretend the source is analog, what
you could be hearing is a "delivery system problem".
If you play a sine wave on some LineOut, and then record
on a LineIn, you may notice disturbances which are not
part of a sine wave. And that will give you some idea
what class of fault this is.

*******

The onboard sound has a positive voltage for the
digital portion of the chip. It also has a positive
voltage for the analog portion. That analog power
source, is a relatively small three terminal regulator.
By using a separate regulated power source, the
intention is to reduce the level of "digital noise"
riding on the motherboard sound power rails. Or on
any analog amp after that point.

It's possible to get inductive coupling into
the onboard sound. That happens when the NIC wires
go too close to the LineOut wires. But that would
not be a likely mechanism for an external USB DAC.
And your motherboard sound is clean.

So at this point, I recommend recording the defective
output, so you can diagnose the fault type.

*******

People who buy "audio workstation" motherboards, they
usually run "DPCLat" or delay procedure call latency
test. But it doesn't work on Windows 10.

The time it takes to service a "delayed procedure call",
is a function of the motherboard performance. If the
BIOS uses the SMM (system management mode) interrupt
mechanism, it usurps the OS completely. A USB DAC might
be waiting for a millisecond for data, until the SMM
routine exits and the OS is running again. When this
happens, it ruins the motherboard with respect to running
audio workstation functions.

If you can find a replacement program for "DPCLat",
one that works on Windows 10, you can check out
your "responsiveness" and see whether real-time
performance is compromised for some reason.

When SMM fires off, the OS doesn't know what happened.
All it could notice, is a high performance clock could
be off by a millisecond. The OS has no other record that
it's been swapped out. Programs like DPCLat, attempt
to quantify this problem, by "indirect measurement".
If the DPC Latency has spikes in it, that's generally
a sign that SMM is active. (It's because we don't know
of any other high-enough-priority activity that can
do that to the OS. Intel made sure that SMM was king.)

Note that there is one hardware event, which is
absolutely huge. When your video card changes
into 3D gaming mode, there is a 15 millisecond
spike in the DPCLat trace. Which implies the
video card driver is "stuck" and holding the
kernel hostage for a frame time, while it
switches modes. Normally, people doing audio
workstation work, aren't screwing with 3D games
in the middle of recording their rock group.
So this isn't a problem. I've not done
extensive testing of what happens to tunes,
when the video card changes modes, so I don't
know what that one sounds like.

Paul
Paul,

Thanks for the incredibly thoughtful and highly technical response.

One possibly important clue I forgot to mention earlier is that there
is no noise coming through the DAC when there is no signal. That in
itself might mean that it's not the USB bus itself that's noisy, but
that the noise is being generated by the SATA controller when the MP3
file is being fetched for playback.

I'm goiong to try other sources as a means of troubleshooting this. If
it is the SATA bus, then I should also get the noise when playing back
a CD (because the SATA controller is fetching the WAV file from the CD
drive). However I would not expect to get the noise when playing
Pandora, as that is purely network traffic and doesn't involve the
SATA bus.

I'll do further troubleshooting and report back on Sunday.

Jerry


I hate computers! I just now got around to messing with the PC again.
I uninstalled the onboard sound via Device Manager, then rebooted and
entered the BIOS to turn it off. I then re-attached my Meridian
Explorer 2 USB DAC and installed the driver for it (even though the
manufacturer claims it works under Windows 10 without drivers, I've
never been able to make that work - I always have to load the Windows
7 driver).

I checked Device Manager, and the Device Properties dialogs in the
Sound section of Settings to make sure everything was looking normal
and set up correctly. Then I figured I'd better confirm the noise
again before trying different things to troubleshoot it. And
naturally, the noise is now GONE.

I want to pound my head against the wall. All that troubleshooting
yesterday was a waste of time. I never did find the cause of the
problem, and I have no idea why it went away.

Guess I won't be buying a new PC after all.

Paul, thank you again for taking the time to provide all that
wonderful advice for me. I really appreciate it. I'm sorry that it
proved unnecessary in the end.

Jerry


So what you discovered was, the noise was indeed temporal
servicing noise, not analog noise, because now the DAC is clear.

And in future, you can test for "responsiveness" on the PC,
as a root cause.

Normally, this should never be a problem. The hardware
interrupts from USB, should be serviced right away.

1) Stub service routine responds practically instantly.
This is the driver in Ring0, down where the kernel lives.
2) Extended service (filling buffer for next time, preparing
DMA chain or whatever), that service request is queued
on the DPC queue. Delay procedure calls run in Ring3,
like they were an application.
3) The OS monitors the DPC queue, and if the OS is falling
behind, it's supposed to have an internal setting where
more of the cores work on reducing the depth of the DPC
queue.

If all of that crap keeps your sound buffer full, there
won't be any of "that kind" of noise.

Paul


Paul, the Meridian Explorer 2 DAC driver installs a small "control
panel" that allows you to tweak some settings for the DAC. I have
left these at the defaults since I never understood what they did, but
in light of my recent experience, do you think I should change any of
the settings? The control panel settings a

USB Streaming mode:

Minimum latency
Low Latency
Standard
Relaxed
Reliable -- Default setting
Safe
Extra Safe

ASIO Buffer Size:

Auto -- Default setting
64
128
256
512
1024
2048
4096
8192
16384

Jerry
  #7  
Old September 3rd 18, 10:18 PM posted to alt.comp.periphs.mainboard.asus
Paul[_26_]
external usenet poster
 
Posts: 888
Default P8Z68/GEN3 Deluxe Noisy USB Bus

Tater wrote:
On Sun, 02 Sep 2018 21:19:35 -0400, Paul
wrote:

Tater wrote:
On Sun, 02 Sep 2018 00:33:43 -0700, Tater wrote:

On Sat, 01 Sep 2018 23:24:49 -0400, Paul
wrote:

Tater wrote:
I was trying to listen to some MP3s on my PC via iTunes, and suddenly
I was like "What the heck - this sounds like crap". I was getting
random clicking and crackling noises. It basically sounded like I was
playing back a badly worn LP.

First I tried the same track several times in a row and confirmed that
the clicks and pops were random - not in the same location in the
track. I tried different tracks from other albums - same story.

Then I turned to hardware troubleshooting - before I tell you about
that let me describe the sound system on my computer:

It's PC to USB DAC to tube preamp to amplified speakers. I am not
using the onboard sound on the motherboard. The USB DAC (digital to
analog converter) is a little gadget like a USB thumb drive that plugs
into a USB port on the back of the PC and outputs an analog signal on
a standard 1/8" phone jack. The tube preamp provides volume control
(and that "good old tube sound"), and the speakers each have their own
amplifiers built in.

First thing I thought was I had a bad connection somewhere. I
unplugged and reseated the DAC and all the analog connections. Didn't
help.

I ruled out a bad speaker because the noise was occurring in both
channels.

Next I pulled out an older DAC and swapped the DACs out. Didn't help.
I moved the DAC to two other USB ports - didn't help.

I moved the DAC to my add-in Inateck USB 3.0 board (I'm not using the
onboard USB 3.0 on this motherboard). This seemed to make the noise
even worse.

To eliminate the tube preamp as a source of noise I disconnected the
preamp and speakers, and plugged a set of headphones directly into the
jack on the DAC. I Still heard the same noises via the headphones.

So now I've isolated the noise all the way back to the PC itself - my
troubleshooting has eliminated anything external to the PC as a
possible source of noise.

I suppose it might be a noisy power supply (and I do have a spare) but
that's a lot of work to change out unless I truly have to.

The only other thing I could think of trying at this point was to
remove the DAC and activate the onboard sound chip on the motherboard,
so that's what I did. Asus had a massive Windows 10 audio driver on
their web site that came out two years ago - but I decided to let
Windows try and install the sound device by itself, figuring I'd
probably get a more up to date driver that way. It did find a driver
for it - it's a pretty basic driver, but I don't need any fancy
features. Pure unadulterated two channel sound is all I was looking
for.

So I hooked up my preamp to the onboard sound port and played an MP3.
Sounds fine, zero noise. I'm not going to say it's as good as the USB
DAC, but it sounds a heck of a lot better than I was expecting.

This leaves questions though. If the power supply was noisy,
shouldn't that noise have permeated the onboard sound system as well?

What is the nature of this noise I'm hearing through the USB DAC? If
there is random noise on my USB bus, I would think I'd be at risk for
corrupted data on USB devices like my big backup drive or my USB thumb
drives?

Any advice is appreciated!

Configuration:

Asus P8Z68 Deluxe/GEN3 motherboard
4x4GB Corsair Vengeance LP DDR3 1600 RAM
Intel i7-2700K CPU
EVGA Supernova 850 T2 power suppy
EVGA GTX 970 FTW+ 4GB video card
SanDisk Extreme Pro 480GB SSD boot drive
2x1TB Western Digital Black data drives
Western Digital 8TB My Book Duo USB backup drive (in Raid 1)
Antec P280 case
Noctua CPU cooler and 3 Noctua case fans
Inateck KTU3FR-2O2I add-in USB 3.0 card
Pioneer 16X Blu-ray burner
Windows 10 Pro version 1803
Meridian Explorer 2 DAC
ifi iTube preamp
Paradigm Shift A2 speakers

Thanks in advance.

Jerry
It sounds like you already have good debugging skills,
so I won't need to add much.

You can record the output of your DAC, using the
onboard sound and the LineIn on it. That's one
possibility.

Using Audacity, you could record the output waveform,
and compare it to your stimulus, and see how the noise
modulates the waveform.

Audacity doesn't support playback and recording at
the same time. Which usually means I need two programs,
one to playback a stimulus and a second program
to record, to get the data I want.

Sometimes clicks or pops, are actually flat spots
caused on the output waveform, by "buffer runs dry".
The hardware has to signal that the buffer is getting
low, and the system coughs up a few packets of
data to fill up some kind of queue. If the queue ever
runs dry (because the buffer cannot be serviced in
time), the last voltage level on the DAC "sits there"
until a packet of new samples arrive. The flat spot
makes an audible noise, although not as loud a sound
as you would think.

When digital samples are corrupted (like the MSBit changes
state), that creates a huge pop. And you'd notice that.

So while it's fun to pretend the source is analog, what
you could be hearing is a "delivery system problem".
If you play a sine wave on some LineOut, and then record
on a LineIn, you may notice disturbances which are not
part of a sine wave. And that will give you some idea
what class of fault this is.

*******

The onboard sound has a positive voltage for the
digital portion of the chip. It also has a positive
voltage for the analog portion. That analog power
source, is a relatively small three terminal regulator.
By using a separate regulated power source, the
intention is to reduce the level of "digital noise"
riding on the motherboard sound power rails. Or on
any analog amp after that point.

It's possible to get inductive coupling into
the onboard sound. That happens when the NIC wires
go too close to the LineOut wires. But that would
not be a likely mechanism for an external USB DAC.
And your motherboard sound is clean.

So at this point, I recommend recording the defective
output, so you can diagnose the fault type.

*******

People who buy "audio workstation" motherboards, they
usually run "DPCLat" or delay procedure call latency
test. But it doesn't work on Windows 10.

The time it takes to service a "delayed procedure call",
is a function of the motherboard performance. If the
BIOS uses the SMM (system management mode) interrupt
mechanism, it usurps the OS completely. A USB DAC might
be waiting for a millisecond for data, until the SMM
routine exits and the OS is running again. When this
happens, it ruins the motherboard with respect to running
audio workstation functions.

If you can find a replacement program for "DPCLat",
one that works on Windows 10, you can check out
your "responsiveness" and see whether real-time
performance is compromised for some reason.

When SMM fires off, the OS doesn't know what happened.
All it could notice, is a high performance clock could
be off by a millisecond. The OS has no other record that
it's been swapped out. Programs like DPCLat, attempt
to quantify this problem, by "indirect measurement".
If the DPC Latency has spikes in it, that's generally
a sign that SMM is active. (It's because we don't know
of any other high-enough-priority activity that can
do that to the OS. Intel made sure that SMM was king.)

Note that there is one hardware event, which is
absolutely huge. When your video card changes
into 3D gaming mode, there is a 15 millisecond
spike in the DPCLat trace. Which implies the
video card driver is "stuck" and holding the
kernel hostage for a frame time, while it
switches modes. Normally, people doing audio
workstation work, aren't screwing with 3D games
in the middle of recording their rock group.
So this isn't a problem. I've not done
extensive testing of what happens to tunes,
when the video card changes modes, so I don't
know what that one sounds like.

Paul
Paul,

Thanks for the incredibly thoughtful and highly technical response.

One possibly important clue I forgot to mention earlier is that there
is no noise coming through the DAC when there is no signal. That in
itself might mean that it's not the USB bus itself that's noisy, but
that the noise is being generated by the SATA controller when the MP3
file is being fetched for playback.

I'm goiong to try other sources as a means of troubleshooting this. If
it is the SATA bus, then I should also get the noise when playing back
a CD (because the SATA controller is fetching the WAV file from the CD
drive). However I would not expect to get the noise when playing
Pandora, as that is purely network traffic and doesn't involve the
SATA bus.

I'll do further troubleshooting and report back on Sunday.

Jerry
I hate computers! I just now got around to messing with the PC again.
I uninstalled the onboard sound via Device Manager, then rebooted and
entered the BIOS to turn it off. I then re-attached my Meridian
Explorer 2 USB DAC and installed the driver for it (even though the
manufacturer claims it works under Windows 10 without drivers, I've
never been able to make that work - I always have to load the Windows
7 driver).

I checked Device Manager, and the Device Properties dialogs in the
Sound section of Settings to make sure everything was looking normal
and set up correctly. Then I figured I'd better confirm the noise
again before trying different things to troubleshoot it. And
naturally, the noise is now GONE.

I want to pound my head against the wall. All that troubleshooting
yesterday was a waste of time. I never did find the cause of the
problem, and I have no idea why it went away.

Guess I won't be buying a new PC after all.

Paul, thank you again for taking the time to provide all that
wonderful advice for me. I really appreciate it. I'm sorry that it
proved unnecessary in the end.

Jerry

So what you discovered was, the noise was indeed temporal
servicing noise, not analog noise, because now the DAC is clear.

And in future, you can test for "responsiveness" on the PC,
as a root cause.

Normally, this should never be a problem. The hardware
interrupts from USB, should be serviced right away.

1) Stub service routine responds practically instantly.
This is the driver in Ring0, down where the kernel lives.
2) Extended service (filling buffer for next time, preparing
DMA chain or whatever), that service request is queued
on the DPC queue. Delay procedure calls run in Ring3,
like they were an application.
3) The OS monitors the DPC queue, and if the OS is falling
behind, it's supposed to have an internal setting where
more of the cores work on reducing the depth of the DPC
queue.

If all of that crap keeps your sound buffer full, there
won't be any of "that kind" of noise.

Paul


Paul, the Meridian Explorer 2 DAC driver installs a small "control
panel" that allows you to tweak some settings for the DAC. I have
left these at the defaults since I never understood what they did, but
in light of my recent experience, do you think I should change any of
the settings? The control panel settings a

USB Streaming mode:

Minimum latency
Low Latency
Standard
Relaxed
Reliable -- Default setting
Safe
Extra Safe

ASIO Buffer Size:

Auto -- Default setting
64
128
256
512
1024
2048
4096
8192
16384

Jerry


Generally, you run an ASIO driver, for minimum latency.
And that means selecting a smaller buffer size, such
that timing-wise, we know the USB can refill the
buffer before it is too late.

If, for some reason, that wasn't important (the low latency)
you could play with the buffer size.

Perhaps the side effect, if it was malfunctioning, is the
frequency of the noise events would change with buffer
size.

Sound doesn't need a lot of bandwidth. The OS can service
at least 10,000 interrupts a second. The only way this
can break, is if something manages to "hog" resources.

For example, in the old days, I could use a "critical section"
around some low level code I've written. Which locks out
the OS for a period of time. A person using such a technique,
asks the system architect, what the max time for a critical
section is, without breaking stuff. And then that person works
on their code, polishing it, so they stay well away from the
breakage point.

That doesn't explain how the video card gets away with
blanking the system for 16 milliseconds when it
switches to 3D mode. But then, we don't have high
expectations on desktop performance while doing that
anyway. I don't think I've heard anyone actually
complain about that (other than to "notice" it in the
DPCLat graph).

Paul
 




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