Since it's a long weekend here in British Columbia, I was thinking today
about that "spectral smearing" which I showed the other day out of the
XONAR Essence One when testing the Touch with various digital cables.

I had noticed this spreading of the base even with my USB playback. As a
result I thought I'd try some measurements to see whether this changes
with the USB port and drivers used...  Lo and behold... It does make a
difference!

When I made that Touch jitter recording, the E1 was connected to my
ASrock Z77 Extreme4's motherboard USB3 port and it looked a bit like
this (DirectSound):
14459

Look what happens when I move it over to the USB2 port (DirectSound):
14460

That "wide base" is now gone and the noise floor is on average slightly
higher but the spikes have cleaned up!  Interesting...  It looks like
there's some kind of interaction between the Essence One and the USB
interface.  Some of this must be the electrical noise from the computer
itself but the decreased spectral smearing probably has to do with less
low level jitter through the USB2.

Also, I decided to try the different driver "modes" as well - here's
ASIO with the USB2 interface (as opposed to the DirectSound driver
above):
14462

The noise floor drops. A nice tangible "proof" that ASIO works better by
directly going to the hardware instead of running through the Windows
mixer even though the volume is 100%.

I guess this highlights the complex interactions between hardware and
software in a computer environment. I can see how folks could agonize
over the details and manufacturers could sell products with claims that
could be "true" (eg. the SOtM tX-USB Audiophile PCI to USB Audio Card
could measure really well compared to my motherboard interfaces). Again,
I really can't say I hear a difference despite the above measurements.
If it weren't for doing these measurements, I would not have known about
these kinds of changes!


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