Cable topologies typically used in audio applications have a significant impact on performance. One size does not fit all. The differences between interconnects (generally) and (specifically) Atlas.

Overview

In a simple physics experiment at school you are given a battery, a light bulb and two pieces of wire and asked to make a lighting circuit. You connect one wire to the positive terminal of the battery and then to the positive terminal of the light bulb, you connect the second wire to the base (negative) of the bulb. When you complete the circuit by attaching the cable to the negative terminal of the battery the circuit is complete and the bulb lights – bravo!

In this respect most circuits work the same, a positive (or signal) conductor carries the current to the load and the negative ( return) conductor completes the circuit. hi-fi interconnect cables work exactly the same way, we have a signal conductor which carries the delicate hi-fi signal from the source ( streamer, CD, pre amplifier etc) to the destination ( pre amplifier, power amplifier etc) and a return conductor which completes the circuit.

As all audio cables transfer musical information between source and destination then the audio quality is affected considerably by the topology and material used in this process. Listed below are various interconnect topologies listed in a hierarchical fashion to help try and demystify the jargon often associated with the selection of hi-fi cables.

Coaxial cables

A coaxial cable has a single central signal conductor (stranded or solid) which transfers the delicate signal between source and destination, surrounded by a metallic shield which is used as a “return” conductor. This unbalanced return whilst providing some form of shield for stray electric fields does not provide any protection from induced magnetic fields.

This cable topology is popular for many reasons:

  • Only a single high quality conductor (stranded or solid) needs to be used for the signal conductor.
  • A cheaper material can be used for the screen (return).
  • When connected between a pre-amplifier and a source component the return conductor is connected to the pre-amplifier 0v and usually then later to ground.
  • As it‘s a coaxial cable it can be designed to have a specific characteristic impedance and in some circumstances can be used for both analogue and digital use.
  • The screening effect of the cable is compromised as signal return currents may also circulate in the screen material.
  • These cables are non-directional by manufacture and can be connected in any orientation straight from the box.

Symmetrical (or dual core) cables

This type of cable again uses a high quality conductor to handle the signal transfer but uses an identical conductor (return) to compete the circuit. These cables most often deliver better audio fidelity than a coaxial cable. These twisted pair designs provide greater immunity to magnetic fields, but without a shield are still susceptible to electrical interference.

  • They present an equal impedance on both circuit paths which is good practice.
  • The electrical characteristics of both conductors are identical which delivers consistent results.
  • When connected to a preamplifier the return conductor is connected to the system 0v and mostly later to the system ground.
  • They however have double the volume of the important signal conductor, so are often at least twice as expensive.
  • They have no shielding and rely on twisting as simple protection.
  • These products are non-directional by manufacture and can be connected in any orientation straight from the box.

Pseudo-balanced cables (symmetrical plus screen)

Cables are shielded to protect sensitive signals from external noise.

There are two generally two types of shield, one to reject electrically induced noise, the other to reject magnetically induced noise. The rejection of electrically induced noise requires the shield to be made of a metal with a high conductivity (since RFI rejection requires ‘shielding’ currents to be able to flow easily in the shield.

In an unbalanced interconnect, the shield also acts as the signal return path, while in a pseudo-balanced RCA configuration the shield and return paths are two identical conductors surrounded by a wrapped/woven screen, with the shield left open at one end. This makes pseudo-balanced interconnects directional by manufacture.

A cable could be wrapped around a ferrite core (iron etc.) to maximize the rejection of magnetic fields. Interconnects incorporating such a shield are bulky, this method of magnetic field rejection is not generally used on hifi. To reject magnetic interference in hi-fi applications, it is usually sufficient to twist the insulated conductors together to form what is known as a twisted pair.

Nowadays technologies such as ‘High Definition Audio’ can produce audio signals well beyond the 20kHz value which was typically considered to be an adequate cut-off frequency for HiFi systems. In response to this, some loudspeaker producers are meeting the latest demands for high frequency extension with highly sophisticated tweeters capable of reproduction well above 20kHz. A few speaker manufacturers provide a ground contact on the speaker so that a drain wire can be connected to reject RFI which can otherwise become an audible problem at frequencies in excess of about 20kHz.

It’s not only the quality/quantity of shielding but also the method of terminating the screens to maximise the Rf performance. At Atlas we utilise a special technique called ‘Dual-Drain’ which not only eases the manufacturing process and maintains the screen integrity but also maximises the screen efficiency to eliminate unwanted noise.

Pseudo-balanced with independent ground (Grun).

The pseudo-balanced cable topology, although offering great performance ,has one small but in hi-fi terms large flaw — the screen when connected to system 0v can be modulated by any circulating currents that exist within the product. In an ideal electrical environment all ground references should be at the same ’potential‘ as not to generate any circulating currents. So the natural extension to the pseudo-balanced cable is the ’symmetrical with independent ground‘ topology.

This involves connecting the cable screen to system ground externally via an independent grounding cable (Grun) and directly to your home ground point (earth). The results are simply outstanding, with no circulating current in the screens and no modulation of the 0v at the screen connection point (in a pseudo-balanced cable), the true capability of the interconnect can be heard, and crucially, demonstrated.

  • The screen is connected directly to ground and not system 0v.
  • The true benefit of the conductor material and dielectric can be delivered.
  • The true constancy of crimping as opposed to soldering can be delivered.
  • These cables are non-directional by manufacture and can initially be connected any way around straight from the box.

Atlas Grun Coherent Ground System.

Using Atlas Grun-enabled cables and adapters, optimum fidelity can be achieved. The benefits of the Grun system are cumulative.

Find out how Grun works and see available* adapters.

*Grun products are normally supplied with a basic adapter, additional adapters and options are available

the performance connection

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