Quad microphone cables DIY into USB cables?

[Rantenti]

Hello all,

There are people making USB cables for DAC from popular quad microphone cables. They are not expensive.

I was wondering, since USB cables are supposed to conform to 90 ohm standard (eg. ifi micro iDSD cannot be recognized by the computer if the USB cable does not follow USB 2.0 standards) and the power line is designed to be isolated from the data lines, but Quad microphone cables are not designed to isolate any one of the conductors specifically, will the use of such cables cause problems in signal transmission (either audible or not)?

Thanks!

 

[wwenze]

There are people DIY-ing USB cables from anything including silver wires. Doesn't mean it works as good as a $3 normal USB cable.

https://www.head-fi.org/threads/diy-usb-cable-with-pure-silver-sound-crackle-noise-plz-help.734213/

But if your question is asking about the other extreme i.e. how bad can my cable be before it stops working, the answer is, very. The wiring between the motherboard and the casing for USB2.0 is often just standard normal wire.

 

[Rantenti]

USB cables made from eg. Canare quad could be had for a few dollars. At least the cable itself is well made.

I had generic USB cables that worked perfectly, but I also had two which either produced no sound or produced stuttering music. Those two were not USB 2.0 "certified".

So I was just wondering how the USB 2.0 standard of 90 ohms and power line shielding factors come into play:

1. will non-90 ohm cables cause more measurable data transmission erros than a USB 2.0 spec cable?

2. will blocking the power terminal in the USB connector thus making the cable data-only reduce transmission errors?

I am asking about measurable differences which may be inaudible.

Thanks.

 

[wwenze]

1. Yes. The end result will be either inconsequential or horribly wrong. For digital it's either it works or it doesn't work, with only a thin region for "works sometimes". For measurement of digital signals we would use an oscilloscope and measure the eye diagram.
https://incompliancemag.com/article/use-the-eye-diagram-to-check-your-connections/

2. IIRC the +ve is not required but the gnd connection is needed to ensure the common mode voltage does not float too far away (max is like maybe 15V or something? that depends on the receiver chip.) That said I have made a cable with an external power supply that has the ground disconnected and it works, so, yea. (I needed to break the ground connection between DAC and PC.)

The carrier frequency of USB2.0 data is in the few hundred MHz, so power noise will look like DC in comparison, except power noise that appear as a result of digital signals themselves. The signal driver uses the same power supply so if there is sufficient noise on the power wire to couple to the signal wire, you should be more worried about the amount of noise on the signal lines instead. Rather, it's more common for the signal lines to be the source of radiated noise for others instead. USB3.0 really ruins wireless mice.

 

[Cbdb2]

You want to use a mic cable to transmit a 250Mhz signal? Why? Wouldnt CAT6 cable, designed for hi freq. digital data be better and cheaper? Actualy, cable designed for USB2 would be best. Dont uderstand why you would make your own.

That 90ohms is the characteristic impedance of the cable. Since your transmiting RF its important. Mic cables never shows the characteristic impedance in the specs because it doesnt matter for mic cables. You will have to measure it.

Not sure about this, but I Think USB will work with marginal cables but it slows down. Since USB 2 is a lot faster than you need for audio it may still work even with lousy cables. If it works it will sound the same so just use real USB cables and save yourself the time.

 

[mansr]

Not sure about this, but I Think USB will work with marginal cables but it slows down.

USB is surprisingly tolerant of bad cables. It will work perfectly up to some point where it falls off a cliff. There is no gradual slowdown.

 

[mansr]

There are people making USB cables for DAC from popular quad microphone cables.

Why, oh why?

 

[mansr]

IIRC the +ve is not required but the gnd connection is needed to ensure the common mode voltage does not float too far away

Both ground and Vbus are required by compliant devices, though Vbus can be supplied by a different source. If either is missing, devices will simply not be detected at all.

That said I have made a cable with an external power supply that has the ground disconnected and it works, so, yea.

That means there is some other ground path between the computer and the DAC. Otherwise the DAC would not be seen.

 

[Rantenti]

USB is surprisingly tolerant of bad cables. It will work perfectly up to some point where it falls off a cliff. There is no gradual slowdown.

I once had two problem cables.

One could be detected by only one of my three DAC devices and on that device, sounds strangely soft with some strange noises which I can only describe as like "echo".

Another was a generic printer cable which worked well with my printer but stutters when connected to my DACs. The music stops and go, jumps a note, stutters and carried on again for a half a second and stutters again.

And I don't know why people would make USB cables out of quad microphone cables. Some suggest their sound characteristics would be the same when made into usb... I would rather not experiment and buy a USB spec compliant cable which I know will work.