Using RCA Interconnect as cable for Digital output

rdevakumar

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My streamer has digital output with specification "Digital output RCA 75 ohms: sample rates up to 192 kHz". To connect my DAC, I am using one of my RCA Cable - Luxman JPR-100, with specification "Conductor resistance: 26.4Ω/km or less (at 20°C)". Do I need to get any specific (matching) cable for optical output to get better quality of sound?
 
My streamer has digital output with specification "Digital output RCA 75 ohms: sample rates up to 192 kHz". To connect my DAC, I am using one of my RCA Cable - Luxman JPR-100, with specification "Conductor resistance: 26.4Ω/km or less (at 20°C)". Do I need to get any specific (matching) cable for optical output to get better quality of sound?
You are fine.
The optical output could have been implemented well so try it out. I tried it and like it and use it.
 
My streamer has digital output with specification "Digital output RCA 75 ohms: sample rates up to 192 kHz". To connect my DAC, I am using one of my RCA Cable - Luxman JPR-100, with specification "Conductor resistance: 26.4Ω/km or less (at 20°C)". Do I need to get any specific (matching) cable for optical output to get better quality of sound?
Hi...I don't know if we can hear a difference between the two. But a coaxial digital cable was designed to have an impedence of 75 ohms. Where as a RCA cable should have a impedence of 50 ohms as per design. Iam not sure if I can hear a difference between the two if I swapped them. So if you are fine with the sound, then absolutely no harm :)
 
My streamer has digital output with specification "Digital output RCA 75 ohms: sample rates up to 192 kHz". To connect my DAC, I am using one of my RCA Cable - Luxman JPR-100, with specification "Conductor resistance: 26.4Ω/km or less (at 20°C)". Do I need to get any specific (matching) cable for optical output to get better quality of sound?
Please use Special 75 coaxial digital canle only for spdif. These will have special shielding to safegaurd the digital signal. RCA is meant to carry Analog signals and analog signals are not prone to outside noise, hence they don't have impedance matching shield
 
Please use Special 75 coaxial digital canle only for spdif. These will have special shielding to safegaurd the digital signal. RCA is meant to carry Analog signals and analog signals are not prone to outside noise, hence they don't have impedance matching shield
True but can you pass a blind test comparing the two ?
 
True but can you pass a blind test comparing the two ?
I can't :D

I have 2 pairs of hifidelity magnetic transmission CT-R1 RCA cables. And just one of their coaxial digital cable. They all look the bloody same, and got mixed up :D

Though I should be able to use a multimeter to measure the impedence at the terminals and make out which is which. But I've never bothered. The mis match between my preamp and poweramp in terms of output and input impedence is so huge, that coaxial digital vs RCA impedence looks puny in comparison :D
 
Quoting from Belden Cables

AES/EBU Digital Audio Cables​

The specification for digital audio was developed jointly by the Audio Engineering Society (AES) & European Broadcast Union (EBU). The key difference between twisted pair specifications for digital audio cable and standard analog audio cable is the impedance specification. AES/EBU, with its broad tolerance, allows cables with impedances from 88 Ohm to 132 Ohm to be used. Standard analog audio cable impedance is 45 Ohm to 70 Ohm. This amount of potential mismatch can result in signal reflections and jitter, causing bit errors at the receiver. For this reason, Belden recommends 100 to 120 Ohm shielded twisted pair cables.
 
for coax duty, the recommended configutation for cable is pure coaxial type with 75 ohm spec, BNC over phono (RCA) if available. Cable length recommended is 1.5 meters. If RCA type cable, connectors need to be close to that specified for digital coax types.
That said all digital coax cables can be used for analogue duty, but vice-versa is avoidable.
 
Analog is also susceptible to noise I don't deny that but in case of digital any impedance misatch from external environment could result in bit error.
These reflections are governed by Fresnel equations and where first developed for optics. But EM radiation also follow the same pattern. The refection that happens depends on the angle of incidence and the refractive index of the material. These become significant for high frequency when the cable starts acting like a transmission line. As the S/PDIF digital signal contains fundamental frequencies of 1.5 and 3 MHz, even quite short S/PDIF cables behave like transmission lines. The same effect also occurs at audio frequencies, but only if the cables are massively long — as in, long like overhead telephone wires between cities!


A signal travelling along an electrical transmission line will be partly, or wholly, reflected back in the opposite direction when the travelling signal encounters a discontinuity in the characteristic impedance of the line, or if the far end of the line is not terminated in its characteristic impedance. This can happen, for instance, if two lengths of dissimilar transmission lines are joined together.
If you are dealing with high frequencies then understanding these reflections become very important.
 
These reflections are governed by Fresnel equations and where first developed for optics. But EM radiation also follow the same pattern. The refection that happens depends on the angle of incidence and the refractive index of the material. These become significant for high frequency when the cable starts acting like a transmission line. As the S/PDIF digital signal contains fundamental frequencies of 1.5 and 3 MHz, even quite short S/PDIF cables behave like transmission lines. The same effect also occurs at audio frequencies, but only if the cables are massively long — as in, long like overhead telephone wires between cities!


A signal travelling along an electrical transmission line will be partly, or wholly, reflected back in the opposite direction when the travelling signal encounters a discontinuity in the characteristic impedance of the line, or if the far end of the line is not terminated in its characteristic impedance. This can happen, for instance, if two lengths of dissimilar transmission lines are joined together.
If you are dealing with high frequencies then understanding these reflections become very important.
Thank you sir for that wonderful technical background.
 
Right now experimenting with a diy interconnect with rca plugs soldered to the most tightly twisted pair of a cat 5 cable(solid core) as a digital interconnect between my digital media convertor and the dac.

Usb in -> cat 5 spdif out -> cat 5 spdif in -> amp.

Sounds alright to me.

Anyone else tried this out ?
 
Right now experimenting with a diy interconnect with rca plugs soldered to the most tightly twisted pair of a cat 5 cable(solid core) as a digital interconnect between my digital media convertor and the dac.

Usb in -> cat 5 spdif out -> cat 5 spdif in -> amp.

Sounds alright to me.
Indeed. The reflections become troublesome only for frequencies in few MHz or when very long.
Anyone else tried this out ?
I use DIY cat5 cables for all my interconnects because they give lower capacitance then most top of the line manufactured cables. I now have a graveyard of manufactured cables which I'm using to harvest the RCA plugs. The RCA made by some company named DAC were the one with highest capacitance.
IMG_20221108_155210.jpeg
 

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Indeed. The reflections become troublesome only for frequencies in few MHz or when very long.

I use DIY cat5 cables for all my interconnects because they give lower capacitance then most top of the line manufactured cables. I now have a graveyard of manufactured cables which I'm using to harvest the RCA plugs. The RCA made by some company named DAC were the one with highest capacitance.
View attachment 73031
Just put back my copper coax.

For analogue applications for cat5/cat6 cables they seem to convey good detail but somehow for one of the genres of music I listen too which is western classical music, they seem to imprint a forward(I dont mind that) yet a bit screechy presentation on the string sections like violins, very sharp on the trumpets and other horns and slightly rolled off on the bottom. All else seems ok. Not sure if you hear that too.

Recently i swapped out my diy headphone amp internal hookup wires as I was getting too much of the above and went back to ofc copper. Things are more under control.

Now the funny thing is I just swapped back to my copper coax to do digital duty from the cat5 as I was noticing the same tonal balance on the cat5(digital duty) after an hour of good listening as when I used the cat5 for analog duty. I know that this should not be the case but it seems be. Or is it the cheap connectors? I am using good quality siemens, molex and lucent cat5/6 cables only. Lets see as we go along. Not giving up on cat5/6 yet.
 
Just put back my copper coax.

For analogue applications for cat5/cat6 cables they seem to convey good detail but somehow for one of the genres of music I listen too which is western classical music, they seem to imprint a forward(I dont mind that) yet a bit screechy presentation on the string sections like violins, very sharp on the trumpets and other horns and slightly rolled off on the bottom. All else seems ok. Not sure if you hear that too.
A perfect cable will have zero resistance, zero inductance and zero capacitance. Consider resistance and inductance in series and capacitor in parallel. The most difficult part is getting very low capacitance. The moment you bring two conductors close to each other, the become a capacitor.

The thing about capacitor is that the impedance decreases more for higher frequencies. Higher the frequency lower the impedance. Since the capacitor is in parallel to the audio input/output, it acts like a short. So higher frequencies get wasted more. If you decrease the capacitance (e.g. put a neutral cable), the quantity of HF will increase. Badly recorded content start sounding bad and that's what happens with me. A bad cable will in fact make it sound better. But I avoid using cables as tone control. Because cables from market will destroy the HF which you cannot get it back. If you have seen my setup, I rather use a graphic equalizer to balance bad recordings.

I see people use cables to correct deficiencies in the system. cable manufacturers exploit this to the fullest extent and members end up spending a tidy fortune on cables when what they are actually doing is tone control.

When I started my journey I have sunk money in cables from Siltech, VDH and others. I stay away from them. Be it interconnect, speaker cables or power cables. Now with streaming business on the rise cable manufacturers are targetting ethernet cables too which will make zero difference to your music. But pyschoacoustics is a real thing and many will hear things which are not there.
 
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A perfect cable will have zero resistance, zero inductance and zero capacitance. Consider resistance and inductance in series and capacitor in parallel. The most difficult part is getting very low capacitance. The moment you bring two conductors close to each other, the become a capacitor.

The thing about capacitor is that the impedance decreases more for higher frequencies. Higher the frequency lower the impedance. Since the capacitor is in parallel to the audio input/output, it acts like a short. So higher frequencies get wasted more. If you decrease the capacitance (e.g. put a neutral cable), the quantity of HF will increase. Badly recorded content start sounding bad and that's what happens with me. A bad cable will in fact make it sound better. But I avoid using cables as tone control. Because cables from market will destroy the HF which you cannot get it back. If you have seen my setup, I rather use a graphic equalizer to balance bad recordings.

I see people use cables to correct deficiencies in the system. cable manufacturers exploit this to the fullest extent and members end up spending a tidy fortune on cables when what they are actually doing is tone control.

When I started my journey I have sunk money in cables from Siltech, VDH and others. I stay away from them. Be it interconnect, speaker cables or power cables. Now with streaming business on the rise cable manufacturers are targetting ethernet cables too which will make zero difference to your music. But pyschoacoustics is a real thing and many will hear things which are not there.

Yes this ethernet cable “thing” is something and the “audiophile” 8-16 port switches 😉
 
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