What’s better RCA-RCA or RCA-BNC (digital)?
Posted by: Consciousmess on 05 April 2018
Apologies for all these interconnect threads, but the forum teaches me a lot and I’m on the verge of buying a top flight digital interconnect. I can see a present opportunity, but it’s S/H so can’t audition.
As the question asks, which is better RCA- RCA or RCA-BNC (my nDAC must remain RCA as Naim informed me, but the nDAC takes BNC, which I think is superior)??
Also, does the cutting off of the two unused pins on the DIN connector improve sound quality? I read that on a website.
Thanks
BNC to BNC is best but if your source doesn't have a BNC socket for its digital output then just go RCA>BNC.
DIN plug unused pin removal - Chord reckoned it might be better (I had a Chord cable in my Naim days that used 3 pins in the DIN plug), due to less mechanical coupling between plug and connector. I wouldn't advise doing this to your normal Naim DIN cables though...
Just as James says above. And please don't go trying to cut off any pins in DIN plugs...
Digital cables are nominally 75 Ohm, so are BNC connectors (digital ones are anyway) RCA are not so partially reflect the signal back down the cable. If you have a BNC on the other end there is a good chance it will absorb the reflected signal.
Absorb a reflected signal - are you sure.... reflections are explained by transmission line theory - and a constant characteristic impedance from source, socket, connecter, cable, connector, socket and sink will result in no loss from the AC/reactive element of the signal as being reflected. Cause impedance differences in the line and this changes and reflections will occur causing losses and efficiency reduces. As far as I am aware once the reflection is superimposed on the signal you have effectively distorted the signal and so can't absorb it. One cant absorb distortion to remove it. However one can work with relatively high level levels of reflection (SWR) before efficiency is seriously impaired - and so I think it is often overstated in our rather inexact uses of 75 ohm cables for SPDIF etc - and not least we are working with digital signal levels where distortions to the encoding only very indirectly and slightly affect the resultant analogue signal.. (through phase distortion form errors in edge detection causing transport clock jitter and system coupling)
There are some specialist 'RCA' connectors / sockets that have been designed to be 75 ohm with the connected 75 ohm CI cable. The CI is determined by the physical geometry of the socket, connector and cable and so is achievable but the standard cheap RCA cable you get from the local electrical store certainly isn't, but even that won't cause massive efficiency losses and so would almost certainly work.. but may 'sound' different. Also remember the system's socket and circuity behind the socket needs to be seen as 75 ohms CI as well.
So in summary if the 'RCA' socket has been designed as 75 ohm along with the connected plug and cable then it will be as effective as BNC. However BNC sockets and plugs are mass produced and are cheaper to work with so as to provide 75 ohm as opposed to RCA which requires specific construction techniques and is rare/more expensive.
Points all taken - thanks.
I knew someone would expand on it and thought it might be you but that was all I was going to write on an iphone, it's a long time since I read about transmission lines. What effect signal reflection has on a digital signal by the time it's been converted to analog I don't know but a Belden 4794R (12 GHz, 4K UHD Precision Video Cable, RG-7 Series, 75 Ohm 16 AWG solid 0.051" silver-plated copper conductor, gas-injected foamed high-density polyethylene insulation, Duofoil® bonded to the core + tinned copper braid shield) let more of the emotion come through in the music when used between a Core and a Rega DACr or a 2qute (not enough in the latter case) than either the Chord digital Clearway or Shawline.