[SlimDevices: Audiophiles] MEASUREMENTS: Computer USB port noise, USB hubs and the 8kHz PHY Packet Noise

[Archimago]

A few more measurements on my system showing the benefits of that
Corning optical cable with my noise-sensitive single ended analogue
pre-amp input.

Also thought I'd run a few hubs to see whether the 8kHz noise changes
much...

Still would love to get a hold of this USB Regen and see what it does in
my system!

'*MEASUREMENTS: Computer USB port noise, USB hubs and the 8kHz PHY
Microframe Packet Noise*'
(http://archimago.blogspot.com/2015/05/measurements-usb-hubs-and-8khz-phy.html)



Archimago's Musings: (archimago.blogspot.com) A 'more objective'
audiophile blog.
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[arnyk]

Post by Archimago
A few more measurements on my system showing the benefits of that
Corning optical cable with my noise-sensitive single ended analogue
pre-amp input.
Also thought I'd run a few hubs to see whether the 8kHz noise changes
much...
Still would love to get a hold of this USB Regen and see what it does in
my system!
'*MEASUREMENTS: Computer USB port noise, USB hubs and the 8kHz PHY
Microframe Packet Noise*'
(http://archimago.blogspot.com/2015/05/measurements-usb-hubs-and-8khz-phy.html)

Seems to shed a lot of light. It hopefully will turn discussion back to
fact-based conversations.


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[SBGK]

Post by arnyk
Seems to shed a lot of light. It hopefully will turn discussion back to
fact-based conversations.

See Uptone are endevoring to produce their own measurements to counter
some of the degenerate attacks from Archie Kruger



Touch optimisations http://touchsgotrythm.blogspot.co.uk/
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[Julf]

Post by SBGK
See Uptone are endevoring to produce their own measurements to counter
some of the degenerate attacks from Archie Kruger

Then we can at least have a rational, fact-based discussion about the
results, instead of having to resort to name calling.



"To try to judge the real from the false will always be hard. In this
fast-growing art of 'high fidelity' the quackery will bear a solid gilt
edge that will fool many people" - Paul W Klipsch, 1953
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[arnyk]

Post by Julf
Then we can at least have a rational, fact-based discussion about the
results, instead of having to resort to name calling.

Don't mention fact based or rational without expecting that it will
bring all of those insults out of the woodwork!

It appears to be how Placebophiles work:

Placebophiles don't want facts, they want illusions.

Placebophiles don't want reason, they want imagination.

Now, I love illusions and imagination, but I also like facts and reason.
Everything in its place, eh? ;-)

But yes I hope that some real measurements will get some kind of a
corresponding response from people with dogs in this fight.


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[Mnyb]

Post by Archimago
A few more measurements on my system showing the benefits of that
Corning optical cable with my noise-sensitive single ended analogue
pre-amp input.
Also thought I'd run a few hubs to see whether the 8kHz noise changes
much...
Still would love to get a hold of this USB Regen and see what it does in
my system!
'*MEASUREMENTS: Computer USB port noise, USB hubs and the 8kHz PHY
Microframe Packet Noise*'
(http://archimago.blogspot.com/2015/05/measurements-usb-hubs-and-8khz-phy.html)

Did I get this right can you actually hear this ? It must be something a
bit odd about the ht bypass input in your preamp ? Is it very high gain
?



--------------------------------------------------------------------
Main hifi: Touch + CIA PS +MeridianG68J MeridianHD621 MeridianG98DH 2 x
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sub.
Bedroom/Office: Boom
Kitchen: Touch + powered Fostex PM0.4
Misc use: Radio (with battery)
iPad1 with iPengHD & SqueezePad
(spares Touch, SB3, reciever ,controller )
server HP proliant micro server N36L with ClearOS Linux

http://people.xiph.org/~xiphmont/demo/neil-young.html
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[Mnyb]

What I mean is that there are potential for further general sound
quality improvement with a better gain structure ?
When I had analog amps I used ones with variable gain settings on the
inputs or attenuators .

And as usual thanks for the interesting measurement and blog.

Is the HT PC much noisier than your other computers ? In your other
blogs you never achieved this result .
Are all your DAC's equally affected ?



--------------------------------------------------------------------
Main hifi: Touch + CIA PS +MeridianG68J MeridianHD621 MeridianG98DH 2 x
MeridianDSP5200 MeridianDSP5200HC 2 xMeridianDSP3100 +Rel Stadium 3
sub.
Bedroom/Office: Boom
Kitchen: Touch + powered Fostex PM0.4
Misc use: Radio (with battery)
iPad1 with iPengHD & SqueezePad
(spares Touch, SB3, reciever ,controller )
server HP proliant micro server N36L with ClearOS Linux

http://people.xiph.org/~xiphmont/demo/neil-young.html
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[arnyk]

Post by Mnyb
Did I get this right can you actually hear this ? It must be something a
bit odd about the ht bypass input in your preamp ? Is it very high gain
?

From the article:

"One could see the "glass half full" when we run into imperfections in
the audio system. For example, it was serendipitous that the Emotiva
XSP-1 pre-amp had such a noise-sensitive unbalanced "HT Bypass" input
that I was able to detect noise and measure it previously."

and

"Okay, to end off... Let me remind everyone one more time that what I'm
measuring with the 8kHz noise here is because of the Emotiva XSP-1's
sensitivity to noise through the "Home Theater Bypass" input. The 8kHz
tone is NOT something I have ever heard / measured coming out of a
reputable DAC's analogue outputs! Nor is it something that's found in
Stereophile USB DAC measurements. If it were not for this noise
sensitivity, I would not even have bothered with looking at ways to
attenuate the computer USB noise. Nonetheless, I think this is an
interesting real-life demonstration of the noise pollution that can come
out of the computer's USB port and a solution that works reasonably
well. I did not bother with jitter tests this time as I have never seen
the Dunn J-Test change in any substantial fashion with the use of a hub
with an asynchronous DAC (see the measurements last time). Think you
have a jitter issue? Save up the cash and buy a better asynchronous USB
DAC - forget cables and tweak products IMO."

I think the first paragraph pretty well says it, and the second one
leaves no questoins.

My read is that the Emotiva XSP-1' "Home Theater Bypass" input is so
sensitive to noise because it is unbalanced, and because it is just
plain atypically sensitive to noise.

Stuff happens!


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[Mnyb]

Ok now I've re-read interesting so the noise actually only appear with
the combination of HT computer - Teac DAC - Emotiva preamp in HT bypass
. So this noise is not even there with the same DAC in normal use ? Or
connected in some other way .

I've was not sure that I understood this right . " things happens " yes
indeed .

Wonder if one could cut of vcc and ground in the USB cable , but Google
tells me that that would not work reliable some receiver chips and
designs actually use the USB bus power for the receiving chip . Wonder
if he uses grounded outlets for power ? , lifting ground somewhere is an
old trick .



--------------------------------------------------------------------
Main hifi: Touch + CIA PS +MeridianG68J MeridianHD621 MeridianG98DH 2 x
MeridianDSP5200 MeridianDSP5200HC 2 xMeridianDSP3100 +Rel Stadium 3
sub.
Bedroom/Office: Boom
Kitchen: Touch + powered Fostex PM0.4
Misc use: Radio (with battery)
iPad1 with iPengHD & SqueezePad
(spares Touch, SB3, reciever ,controller )
server HP proliant micro server N36L with ClearOS Linux

http://people.xiph.org/~xiphmont/demo/neil-young.html
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[arnyk]

Post by Mnyb
Ok now I've re-read interesting so the noise actually only appear with
the combination of HT computer - Teac DAC - Emotiva preamp in HT bypass.

Yes

Post by Mnyb
So this noise is not even there with the same DAC in normal use ? Or
connected in some other way .

Yes and yes.

Post by Mnyb
I've was not sure that I understood this right . " things happens " yes
indeed.

Yes

Post by Mnyb
Wonder if one could cut of vcc and ground in the USB cable , but Google
tells me that that would not work reliable some receiver chips and
designs actually use the USB bus power for the receiving chip . Wonder
if he uses grounded outlets for power ? , lifting ground somewhere is an
old trick .

In this case you also have to do something about the signal wires, and
provide a power supply with a separate ground.

The Corning optical cable addressed the signal wires, but seems to have
blown it with the power wires.

My idea was to go down a separate somewhat older but still widely used
path: Transformers.

USB Baluns for CAT 5 go down that road. Just have to get one with enough
bandwidth, and a separate power supply for the far end.


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