[dzasta]

Coming from a simple non technical background I agree that the data is not being changed ( lets assume the USB cables just work and the data is not changed ).

Can it be that different USB cables pass on this interference (noise) in varying degrees, while the digital data stays intact the SQ changes depending on USB cable's interaction on noise?

In its simplest form, data (in digital form) will either get to its destination or it won't. Meaning, digital data traveling from the HIFI server to the DAC through the USB cable will either get there in its original form or not. Transmission of data through a USB cable cannot, will not alter the digital data in any way, shape or form. It's a "1" or a "0". "Yes" or a "no".

Interference in the form of ground noise that may be present on the USB shielding or USB GND lines is filtered out at the DAC and in most cases should never make it to your ears at all (assuming the DAC is functioning properly).

This next part seems to be where most people get their panties in a bunch. The difference you hear is all in your head. There is no actual difference between difference USB cables. Period. We have proven this over 46 unfortunate pages of this thread using commonsense, logic, and most importantly, science, from countless qualified sources. Your mind is a powerful thing and nobody likes to hear that what they are clearly hearing with their own ears is indeed their brain playing a trick on them. Placebo is real.

 

[amirm]

The cable can't introduce noise (USB cables are shielded and the differential twisted pair carrying the signal is remarkably good at rejecting noise, 50dB to 70dB per pinnahertz). That noise would have to be introduced on the USB power line by the transmitting device (e.g. a poorly designed USB PHY). This would then need to be compounded a USB PHY design on the receiving device not be able to reject noise on the power line and also using the USB power line to power the device with little or no filtering (insanely bad design).

Well, insanely bad design from a super popular brands unfortunately exist. See my measurements of a few USB cables and impact on actual output of a DAC:

Now this doesn't mean an audiophile cable is better (see my tests). It is just that this is not a matter of impossibility. There is a USB bus whaling inside the DAC and must be isolated very well from the rest of DAC.

 

[bigshot]

This next part seems to be where most people get their panties in a bunch. The difference you hear is all in your head. There is no actual difference between difference USB cables. Period.

Inaudible is inaudible. A USB cable is a USB cable. Either it works for the purpose, or it's broken.

 

[colonelkernel8]

Well, insanely bad design from a super popular brands unfortunately exist. See my measurements of a few USB cables and impact on actual output of a DAC:

<image redacted for brevity>

Now this doesn't mean an audiophile cable is better (see my tests). It is just that this is not a matter of impossibility. There is a USB bus whaling inside the DAC and must be isolated very well from the rest of DAC.

Methinks there is something else going on here. I would need to see the schematic of the USB input of the Modi 2 since the results were not replicable across different DACs. To be quite frank I wouldn't be surprised to see a somewhat poor design in the Modi 2...this is a $100 "audiophile" DAC. They are going to shave part costs in some areas so they can afford an absolutely insanely over-specced DAC chip that has specs they can market.

 

[bigshot]

Methinks there is something else going on here.

Look at the key on the side... The noise is all below -125dB.

 

[colonelkernel8]

Look at the key on the side... The noise is all below -125dB.

Missed that. Good grief, a bat couldn't hear that. That's below the THD+N of Audio Precision's highest end analyzer.

 

[Glmoneydawg]

Look at the key on the side... The noise is all below -125dB.

100% true....but the graph kinda flies in the face of "they're all the same"....audible?maybe to a bat....still obviously different though.

 

[Glmoneydawg]

Missed that. Good grief, a bat couldn't hear that. That's below the THD+N of Audio Precision's highest end analyzer.

Lol...we both have high regard for bats as audiophiles

 

[colonelkernel8]

100% true....but the graph kinda flies in the face of "they're all the same"....audible?maybe to a bat....still obviously different though.

"Obviously different"? Not so fast. These measurements are below the usable range of the AP analyzer amirm is using...by a lot. The first useful level at this bandwidth (at best, assuming amirm is using the APx555, a $28,000 piece of kit) is the TOP of the chart he's provided here.

Just to be clear: -125 dbV is a signal that is 5e-7 Vrms. Assuming this is 1.5 Vrms (the output of the Modi 2) signal he's performing the FFT on, well, the signal is 2.5 MILLION times larger than the noise.

 

[Glmoneydawg]

"Obviously different"? Not so fast. These measurements are below the usable range of the AP analyzer amirm is using...by a lot.

Even if it its inaccurate you would think they would still be very similar right?Just asking. ..suspect you may know better.

 

[colonelkernel8]

Even if it its inaccurate you would think they would still be very similar right?Just asking. ..suspect you may know better.

At these levels, it could be anything affecting the test platform. Really. These are microvolts. You'd need a spectrum analyzer to accurately measure this.

 

[Glmoneydawg]

"Obviously different"? Not so fast. These measurements are below the usable range of the AP analyzer amirm is using...by a lot. The first useful level at this bandwidth (at best, assuming amirm is using the APx555, a $28,000 piece of kit) is the TOP of the chart he's provided here.

Just to be clear: -125 dbV is a signal that is 5e-7 Vrms. Assuming this is 1.5 Vrms (the output of the Modi 2) signal he's performing the FFT on, well, the signal is 2.5 MILLION times larger than the noise.

At these levels, it could be anything affecting the test platform. Really. These are microvolts.

So we are well below the threshold of audible sound....but they are still different my friend.

 

[colonelkernel8]

So we are well below the threshold of audible sound....but they are still different my friend.

Sure. But only if you're using a Modi 2 and a long USB cable.

 

[Glmoneydawg]

At these levels, it could be anything affecting the test platform. Really. These are microvolts. You'd need a spectrum analyzer to accurately measure this.

Just to be clear as long as cable is able to carry voltage/amps/load(no brainer here) it should be pretty much perfect...this has to be in non-digital electronics?

 

[Glmoneydawg]

Sure. But only if you're using a Modi 2 and a long USB cable.

Lol...we are getting to the same place.