The first photo you posted shows 3 flat - red, white and black plus a bare copper shield
Flat Cable Wire Stripper
- Thread starter AlgoRhythms
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NoisyIndividual
Well-known member
If that is bare copper shield wire, then maybe it acts as an overall screen together with what I suggested was a layer of black semi conductive material on the inside of the blue jacket.
From what I’ve seen from other pics it looks like a complete coverage shield and I agree it’s likely the inside sheath is conductive material. They quote noiseless shielding which would tend to support that.
yes, my bad. one of the 4 conductors I had stripped to show stranded wire. This was misleading.
Shielding is an interesting topic. The best sounding wire, IMO, has no shielding. The wire with robust shielding is quiet but doesn't sound as good.
Ah - so there is no shielding copper so it may be a conductive shield. Or no shield.
I’d be putting a meter probe into the sheath material at each end of your cable and with the meter on ohms setting see if you do have a conductive shield. If there is none then I wouldn’t be using this wire for a low signal cable.
It depends on what bugs you the most. Loss of high end from conductor to shield capacitance or a gaussian noise floor. I'll take a gaussian noise floor over high end roll off any day of the week.
I completely agree. A cable designer friend of mine spent more than a year listening to how shielding effects the sound of analog interconnects to come up with a good compromise for hi RF places like NYC.
Use an appropriately low impedance output driver. How long are your cables that you have problem with capacitive roll-off?
RF interference is typically not Gaussian, it tends to be periodic, or semi-periodic, or correlated with the audio signal as the RFI changes the device operating points.
That's not always possible when using commercial gear. I'm using Gotham GAC-2 in my console. It's about the best shielded cable out there. I am getting some high frequency loss. I'd say most of the time there is between 50 and 100ft of cable in the signal path. All my buildout resistors are 47Ω. I'm going to experiment with changing them to 22Ω to see if I can improve HF performance without making anything unstable.
Right, that's why I picked Gotham GAC-2. My noise floor is beautifully gaussian.
You need really long high capacitance cable to get HF rolloff. Most decent audio cables have very low capacitance anyway. Any unshielded cable is capable of becoming an antenna when connected to any semiconductor in a circuit which can act as a detector and will impart any AF that it carries into that circuit - as all circuitry refers to audio ground, there is a direct connection to any diodes or IC’s via ground in most cases, the ground cable itself can become an antenna and cause breakthrough into the signal path. The shield of an audio cable if part of the audio ground becomes an antenna which can inject interference - like unbalanced Hi-Fi cables. A properly set up audio system using balanced cables will have the internal ground cable connecting the audio boards plus of course your hot and cold cables, the shield of the cable connected to the plug and socket bodies and associated casework and mains earth, audio ground remaining unconnected to chassis until connected at a star ground where the mains earth is taken off - this way the interference from shielding and casework being carried straight to earth, does not enter the audio boards of any gear. Unshielded cable is a disaster around cell phones as when they regularly ping the cell tower you get radiated interference which is quite audible. Digital or audio signals transmitted via RF at reasonable power can break into audio circuits that are unshielded.
100ft is 0.03km. Gotham GAC-2 datasheet claims 135nF/km conductor to shield, so 100ft would be 4nF. 50nF conductor to conductor, so let's round up and say 200nF/km total from each conductor, or 6nF for 100ft. If the 47 Ohms build out dominates the impedance (let's round up to 50 to make the math easier) then the single pole -3dB frequency would be 1/2*pi*50*6e^-9=531kHz.
I would not expect a single pole RC filter at over 500kHz to have any noticeable effect in the audio band. Might be something else going on.
Mogami Neglex 2534 has better conductor to shield specs and not as good conductor to conductor specs. Whichever way you look at it if you get audible HF loss in a 100ft cable there’s something wrong. I’ve done live outdoor setups with 500ft mic cable runs with no problems. I’ve been doing cabling for studios for decades and never had issues with HF loss due to cabling provided the cabling is of sufficiently high quality. The work I do in a studio recording, mixing or mastering is going to end up being played back on a system way inferior to what the music was produced on with crappy cables or Bluetooth speakers or heard on buds or earphones of dubious quality. The main goal is to get the best audio performance from every element in the chain and to minimise external influence as in RF interference, hum, outside sound breakthrough, studio acoustics and so on. These you can’t get rid of from the audio. Room cancellations due to wall and ceiling reflections and subsequent reproduced audio dips and peaks can far outweigh any slight HF loss from an audio cable.
In a recording studio any cable loss is made up for in the mixing stage by simple application of EQ without even thinking about it. There’s a lot of voodoo around some audiophile cables and their perceived merits over standard audio cables but in the studio when you’re listening back to the monitors the sound has been tailored and will have already taken care of any cable induced losses, just like we take care of mics with not a lot of top end (all mics have a very lumpy frequency response anyway).
In a recording studio any cable loss is made up for in the mixing stage by simple application of EQ without even thinking about it. There’s a lot of voodoo around some audiophile cables and their perceived merits over standard audio cables but in the studio when you’re listening back to the monitors the sound has been tailored and will have already taken care of any cable induced losses, just like we take care of mics with not a lot of top end (all mics have a very lumpy frequency response anyway).
Possibly. I haven’t measured at every point in the chain to see exactly how and where it is rolling off. I must say I’ve run the spec sheet numbers of cable and it rarely matches what I measure or hear.
Maybe impedance bumps at connectors? I dunno but this isn’t the first time I’ve seen this with cables that are supposed to measure differently?
Impedance mismatch gear to console perhaps? Where are you hearing the losses ie. what’s the chain?
When I built each active stage I made sure they were flat to 50K. Can someone tell me whether the cumulative rolloff of say 10 active stages with a 50K bandwidth will roll off at 20K with 100ft of GAC2? Everything in series. Measure at the end of the chain.
Unshielded twisted pair relies solely on the CMRR of the receiver for noise rejection. UTP is fine into a transformer input because of the superior CMRR of a transformer. Into an active input, less so.
100ft total for all stages inclusive? For a single 100ft cable with capacitance of 55nF/Km (55pF/M) conductor to conductor, the rolloff frequency would be for a 600Ω output 160KHz approx. However with the conductor to shield capacitance at 135nF/Km (135pF/M) for each conductor, if we added the capacitances together ([135pF/M + 55pF/M = 190pF/M] @ 100ft - 30M length) parallel capacitance calculated separately for each conductor, the rolloff at 3dB, per conductor would be at 46.5KHz.
The lower the source impedance the higher the cutoff.
If each run is only 10ft the 3dB cutoff would be around 465KHz for 600Ω impedance. So as far as cumulative rolloff being a problem the frequency is too high for it to matter. The input impedance at the input can usually be ignored for rough calculation as it is generally way higher.
To do it properly you would need to factor the source impedance of each stage against the length of each segment of the run and the capacitance per Meter. Anything with high source impedance will bring your rolloff frequency down.
Brian Roth
Well-known member
I'm just "winging it" as my best friend often says.....
OK...ignore the cable issues. Ten stages in series with a 50 kHz roll off for each? How far down at 50K for each? They all cascade....
Bri
