Jump to content
IGNORED

Measuring a directional cable


mansr

Recommended Posts

What differences can be measured between the "forward" and "reverse" directions of a 1-metre AudioQuest Tower interconnect? Exotic physics (sci-fi) aside, an asymmetric shield construction could influence its susceptibility to external electromagnetic noise. To test this, I connected an iFi Nano DAC to a Tascam UH-7000 ADC using said interconnect. To create some noise, I wrapped it twice around a mains-powered electric drill running at full speed (everything is more fun with power tools).

 

This is the spectrum of a recording of the DAC playing silence:

aq-drill.png

 

The overall noise floor appears to be a little higher in the reverse direction. There are also clear noise spikes at 6 kHz and 12 kHz.

 

Zooming in on the spikes:

aq-drill-6k.png

aq-drill-12k.png

 

The 6 kHz peaks are somewhat lower in the forward direction, although this could also be the result of the cable not being in exactly the same position. I don't know why the frequencies are different, though the electric drill is hardly a precision instrument, so random variation is a possibility. Repeating the test a few times would be necessary to determine this, but the drill is loud and I'm lazy.

 

To put this in perspective, here is the spectrum of the DAC playing a 1 kHz tone:

aq-drill-1k.png

 

The interference from the drill is far below the harmonic distortion of the DAC.

 

As a reference point, I also did a recording with the drill running in the same location but without the cable wrapped around it. In this case, no visible spikes appear in the spectrum.

 

From this limited test, I conclude that there may be some slight differences in shielding performance. More rigorous testing would be needed to say anything with certainty. What appears to be certain is that in either direction, the shielding is adequate to reduce fairly severe interference to well below audible levels.

Link to comment
What differences can be measured between the "forward" and "reverse" directions of a 1-metre AudioQuest Tower interconnect? Exotic physics (sci-fi) aside, an asymmetric shield construction could influence its susceptibility to external electromagnetic noise. To test this, I connected an iFi Nano DAC to a Tascam UH-7000 ADC using said interconnect. To create some noise, I wrapped it twice around a mains-powered electric drill running at full speed (everything is more fun with power tools).

 

This is the spectrum of a recording of the DAC playing silence:

[ATTACH=CONFIG]29953[/ATTACH]

 

The overall noise floor appears to be a little higher in the reverse direction. There are also clear noise spikes at 6 kHz and 12 kHz.

 

Zooming in on the spikes:

[ATTACH=CONFIG]29954[/ATTACH]

[ATTACH=CONFIG]29955[/ATTACH]

 

The 6 kHz peaks are somewhat lower in the forward direction, although this could also be the result of the cable not being in exactly the same position. I don't know why the frequencies are different, though the electric drill is hardly a precision instrument, so random variation is a possibility. Repeating the test a few times would be necessary to determine this, but the drill is loud and I'm lazy.

 

To put this in perspective, here is the spectrum of the DAC playing a 1 kHz tone:

[ATTACH=CONFIG]29956[/ATTACH]

 

The interference from the drill is far below the harmonic distortion of the DAC.

 

As a reference point, I also did a recording with the drill running in the same location but without the cable wrapped around it. In this case, no visible spikes appear in the spectrum.

 

From this limited test, I conclude that there may be some slight differences in shielding performance. More rigorous testing would be needed to say anything with certainty. What appears to be certain is that in either direction, the shielding is adequate to reduce fairly severe interference to well below audible levels.

 

 

I'm not sure to what to attribute that behavior. As you say, your test, while interesting, is certainly not very rigorous. Certainly, quasi-balanced leads are not ideal in that while the return for the signal IS inside the shield, the shield and the return are still at the same potential. Perhaps some noise is leaking around the barrel of the end that is NOT connected to the shield, giving slightly more noise in the one direction than in the other. Oh, well another audio mystery for the neurotic contingent of the audiophile community to fret over. It's certainly not great enough in amplitude for me to overly concern myself about - especially if I keep electric drill motors from being coiled-up in my cable runs. :)

George

Link to comment

Nice job showing there may be differences in direction.

 

I once wrapped some AQ IC twice around a PC 500 watt power supply while heavily loading the computer it was supplying. This resulted in some barely audibly garbage maybe at -70 db. I didn't try it in reverse direction however. Unwrapping and moving 6 inches (15 cm) away drops all noise below my ability to measure it. Doing the same with generic no name XLR's wrapped 5 times around the same power supply picked up nothing at all I could measure.

 

So if I make my own IC, drive a copper rod into the ground, and wrap a shield connected at the middle going toward both ends (but not connected to the IC electrically) do you think it would improve sound quality and do you think I would have a true bidirectional cable that sounds the same both ways? Maybe I could whip up a patent for that and sell product. True audiophile cables without arrows. Maybe I'll call them Arrowless Voids.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

Link to comment

I always measure the length of the cable in both directions. The direction that measures the shortest always sounds better.

Even the end that the screen is connected to with single ended cables is not clear. Most recommend connecting at the source. There are some manufacturers that recommend the screen connection be floated at the source.

I try to use good quality balanced connections when possible.

 

2012 Mac Mini, i5 - 2.5 GHz, 16 GB RAM. SSD,  PM/PV software, Focusrite Clarett 4Pre 4 channel interface. Daysequerra M4.0X Broadcast monitor., My_Ref Evolution rev a , Klipsch La Scala II, Blue Sky Sub 12

Clarett used as ADC for vinyl rips.

Corning Optical Thunderbolt cable used to connect computer to 4Pre. Dac fed by iFi iPower and Noise Trapper isolation transformer. 

Link to comment
I don't see what the big deal is. If your cables have arrows, point them in the right direction and forget about it. Its not like you're paying extra for directional cables, so who cares?

 

There may not be a big deal, even with quasi-balanced, two conductor plus shield interconnects. It might come down to a question on some systems or components of which component has the best path to ground for the shield-connected end. And, probably, for example if everything is connected to one power circuit, meaning one ground, there may be no difference.

 

In my unbalanced interconnect days, though, I tended to believe in "star grounding" the interconnects, pointing all the arrows away from a single point - the preamp. That was after I realized that the arrows were just about the shield connection and had nothing to do with "signal flow", which is AC in any case. My components were connected to multiple power circuits. But, did it sound better that way? Who knows? I just did it and there were no ill effects.

 

Incidentally, I am all balanced XLR at this point, which are a pleasure to use. I am done with crappy RCA connectors.

 

And, of course, the directional signal flow mythology has spread to unshielded speaker cables, Ethernet cables, etc. My view of any manufacturer who does that is that he is trying to mess with our minds using BS. I walk away from any and all of their products.

Link to comment
I don't see what the big deal is. If your cables have arrows, point them in the right direction and forget about it. Its not like you're paying extra for directional cables, so who cares?

 

Do you know what the right direction is? Hint: It is NOT signal flow!

George

Link to comment

I like to point one channel in one direction and the other opposite. I know it won't be best, but I also know it won't be the worst. :)

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


×
×
  • Create New...