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We know (from reading other audiophile accounts on other forums) that the feeding a DAC is an inherently risky, complex, and difficult task. Everything related to the endeavor can cause tremendously audible differences in the resulting sound. USB connections especially have seemed like one big mistake to pursue. Starting with the computer as source one may need a linear rather than switching supply for the beastly machine. One must choose the playback software carefully or disaster could result. One then needs a USB cable. Should one be so foolish as to simply connect a simple cable then no hope is left for pleasing musical results. At a minimum you need a linear supply for the USB 5 volt lines, a USB filtering reclocking device (one is well advised to spend 300% of the cost of the DAC on the USB connection). Then one should feed the DAC itself with nothing if not a linear PS with audiophile approval.
I thought I would provide some data on just how large the effect of poorly done connections and a lack of care in use of a PC source for music via USB really is. Please, don't try this at home. The variability in sound can be maddening.
At the core of my examination the components that did not change. I used a Focusrite Forte for the DAC. Attached to a wall wart PS. Horrifyingly connected via the stock 1 meter clear shielded USB cable without any intervening protection. It fed via balanced connection an Antelope Audio Zen Tour ADC. Also carelessly connected via the stock 2 meter shielded USB cable. Powered by the wall wart power supply. The Forte was operating at 48 khz and the Zen Tour was recording at 192 khz.
Source computers:
Circa 2010 Lenovo T410 laptop running Windows 10 Creators Edition with spinning 5400 rpm HD and 4 gig of ram (powered by a wall wart).
2014 Apple Macbook Pro with SSD and 8 gig memory powered by the battery.
In the green graphs the Macbook was connected to the Forte and the Zen Tour was feeding the Lenovo. In the blue graphs computers were reversed. And with predictable consequences I might add.
Now for the results.
First I'll show the 300 hz and below FFT while a 1 khz tone is being played looking for corruption by the power supplies bleeding through.
Next I'll show the silent noise floor. The little pip at 31 khz is an idle tone in the Forte DAC.
Now the 1 khz high level tone.
-4 db of white noise. Please steel yourself before viewing the result.
Now I think you can handle the 18+19khz IMD tone result.
As a bonus, we'll look at a portion of a twin tone sweep at near max level. Two tones placed 1 khz apart and swept across the band. Near 19 khz in this image.
Hopefully, these sobering results will prevent other audiophiles from thinking one can grab any old PC lying about and chuck the nearest handy USB cable into the USB jack on a DAC and expect music to result.
I thought I would provide some data on just how large the effect of poorly done connections and a lack of care in use of a PC source for music via USB really is. Please, don't try this at home. The variability in sound can be maddening.
At the core of my examination the components that did not change. I used a Focusrite Forte for the DAC. Attached to a wall wart PS. Horrifyingly connected via the stock 1 meter clear shielded USB cable without any intervening protection. It fed via balanced connection an Antelope Audio Zen Tour ADC. Also carelessly connected via the stock 2 meter shielded USB cable. Powered by the wall wart power supply. The Forte was operating at 48 khz and the Zen Tour was recording at 192 khz.
Source computers:
Circa 2010 Lenovo T410 laptop running Windows 10 Creators Edition with spinning 5400 rpm HD and 4 gig of ram (powered by a wall wart).
2014 Apple Macbook Pro with SSD and 8 gig memory powered by the battery.
In the green graphs the Macbook was connected to the Forte and the Zen Tour was feeding the Lenovo. In the blue graphs computers were reversed. And with predictable consequences I might add.
Now for the results.
First I'll show the 300 hz and below FFT while a 1 khz tone is being played looking for corruption by the power supplies bleeding through.
Next I'll show the silent noise floor. The little pip at 31 khz is an idle tone in the Forte DAC.
Now the 1 khz high level tone.
-4 db of white noise. Please steel yourself before viewing the result.
Now I think you can handle the 18+19khz IMD tone result.
As a bonus, we'll look at a portion of a twin tone sweep at near max level. Two tones placed 1 khz apart and swept across the band. Near 19 khz in this image.
Hopefully, these sobering results will prevent other audiophiles from thinking one can grab any old PC lying about and chuck the nearest handy USB cable into the USB jack on a DAC and expect music to result.
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