Cables are cables and there is no difference?!
I designed a test to see if they perform significantly different in therms of "magnetic shielding" or Leakage inductance.
This test dose not test for ground loop currents but interference from close by magnetic in homogeneous magnetic files.
The basic setup looks like this but in my Case i use 47Ohms and not 1Mohm butt what ever the input impedance of the UMC404HD is
Absolute Vales are not important as we are making a relative comparison.
i turned the gain of the interface all the way up. so expect to see noise... then i made the extra effort to calibrate with a -50dBV source
In the Top right corner we measure -50.02dBV but if we look at the graph we only see about -65dB this is because of fft windowinng loss https://www.recordingblogs.com/wiki/scalloping-loss
So just add about 15dB to what you read in the graph or don’t since we anyways only comparing.
My first idea Was to just put the cable Close to switch mode power supply.
But my laptop Power supply seams to do spread spectrum and is very load dependent. so i tested a USB power supply with a LED lamp as fixed load
Dayum the USB power supply at ~50Khz but i can clearly see it If i hold the cheap generic Cable close to it.
So the setup Seems to work...
Now we just need a better magnetic interference source in the audible spectrum with similar amplitude...
So i placed a Conventional transformer right on top of the Caleb under test.
And run the first round of tests with this Cables:
A "facy" Monster cabel "Xtra Low Noise DoubelHelical^tm Audio Cabel
Cheap but good looking Philips cable with big screen.
A rg174 coax ( I think ) with SMA to RCA adapters.
Cheap generic crap cable
And Telecom Twisted pair phone cable with foil shield.
First the monster Cable under the transformer:
50Hz and 150Hz at ruffly -115dBV (or -87,7dBV if we account for fft loss)
Now Nice looking Philips cable:
About the same little lower 50hz and 250hz peak
Now the RG-something Coax:
Well nothing... or At least nothing i can measure behind the background noise of my crapy audio interface.
Now it gets bad the nasty Generic cabel:
150Hh at over -100dBV and some higher harmonics visible
Telecom Twisted pair with screen connected to one side (j9 or both sides(k):
So its about 5dB better with screen an About the same as -115dBV range as the other cables.
TL;DR
Generic ~ -84dBV @150Hz
Monster and Philips ~ -96dBV
Telecom Twisted pair with shield ~ -99dBV
RG Coax < -107dBV
Can you hear -84dBV?
Don’t know don't care and "it depends"
As i said multiple times this is all relative and the relative take away is.
A ideal cable can be >23dB better as a cray cable and and about 10dB Better Relative to a "monster" or Philips Cable
Do you need 10 to 23dB lower noise? Well if you don't hear any noise probably not!
I designed a test to see if they perform significantly different in therms of "magnetic shielding" or Leakage inductance.
This test dose not test for ground loop currents but interference from close by magnetic in homogeneous magnetic files.
The basic setup looks like this but in my Case i use 47Ohms and not 1Mohm butt what ever the input impedance of the UMC404HD is
Absolute Vales are not important as we are making a relative comparison.
i turned the gain of the interface all the way up. so expect to see noise... then i made the extra effort to calibrate with a -50dBV source
In the Top right corner we measure -50.02dBV but if we look at the graph we only see about -65dB this is because of fft windowinng loss https://www.recordingblogs.com/wiki/scalloping-loss
So just add about 15dB to what you read in the graph or don’t since we anyways only comparing.
My first idea Was to just put the cable Close to switch mode power supply.
But my laptop Power supply seams to do spread spectrum and is very load dependent. so i tested a USB power supply with a LED lamp as fixed load
Dayum the USB power supply at ~50Khz but i can clearly see it If i hold the cheap generic Cable close to it.
So the setup Seems to work...
Now we just need a better magnetic interference source in the audible spectrum with similar amplitude...
So i placed a Conventional transformer right on top of the Caleb under test.
And run the first round of tests with this Cables:
A "facy" Monster cabel "Xtra Low Noise DoubelHelical^tm Audio Cabel
Cheap but good looking Philips cable with big screen.
A rg174 coax ( I think ) with SMA to RCA adapters.
Cheap generic crap cable
And Telecom Twisted pair phone cable with foil shield.
First the monster Cable under the transformer:
50Hz and 150Hz at ruffly -115dBV (or -87,7dBV if we account for fft loss)
Now Nice looking Philips cable:
About the same little lower 50hz and 250hz peak
Now the RG-something Coax:
Well nothing... or At least nothing i can measure behind the background noise of my crapy audio interface.
Now it gets bad the nasty Generic cabel:
150Hh at over -100dBV and some higher harmonics visible
Telecom Twisted pair with screen connected to one side (j9 or both sides(k):
So its about 5dB better with screen an About the same as -115dBV range as the other cables.
TL;DR
Generic ~ -84dBV @150Hz
Monster and Philips ~ -96dBV
Telecom Twisted pair with shield ~ -99dBV
RG Coax < -107dBV
Can you hear -84dBV?
Don’t know don't care and "it depends"
As i said multiple times this is all relative and the relative take away is.
A ideal cable can be >23dB better as a cray cable and and about 10dB Better Relative to a "monster" or Philips Cable
Do you need 10 to 23dB lower noise? Well if you don't hear any noise probably not!
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