Jimbos Audio ramblings

[Barry]

At the risk of triggering a cable discussion is there a case then for spending good money on better interconnects?

In a word, yes. Avoid the freebie cables with moulded on plugs that often come with audio equipment and buy cables that have braided rather than a lapped screen.

But don't go over the top with cost, and don't be fooled by claims that one type of RCA connector is better than another - they are all lousy, but unfortunately we are stuck with them.

If you are handy with a soldering iron, then make your own using a sensible professional cable such as the Belden cable Adrian uses.

[Macca]

Enjoying a day off Mart? One of the few good things about being a grown up is you don't need a note from your mum

Yes, was in Liverpool all weekend so need a day to recover.

[Pigmy Pony]

Yeah that makes sense. But what do people who live there do to recover? Maybe they're used to it.

[Jimbo]

There are no electrons or ions moving around outside. If there were they would be moving in the air outside the cable.

What might exist outside are alternating electric and magnetic fields, and with a cable with poor screening these external fields will interact with the internal fields (due to the audio signal) and affect the signal. But to do so the cable has to have poor screening efficiency (as expressed by the surface transfer impedance Z_t) and the interfering fields have to be very high.

Ah that's what they are but I presume caused by the electrical activity going on in the cable?

[Macca]

Yeah that makes sense. But what do people who live there do to recover? Maybe they're used to it.

They're in training since birth. So was I but mine ended at 18 whereas theirs has continued.

Went out drinking with one of my brother's father-in-law. He's 75. When I was on my fourth pint he was on his twelfth. Just swilling it back - 'Ale doesn't affect me at all.'

By ten o'clock I was going home to bed, he was just moving on to the next pub of the night.

[Barry]

Ah that's what they are but I presume caused by the electrical activity going on in the cable?

Yes, the interference can only be caused by near adjacent cables, but to have an effect the screening of the audio cable would have to be poor. Also since in a mains cable the L and N wires are adjacent and run very close together within the outer sheath, separated by their own insulation, the fields they generate are almost mutually cancelling.

Unless there is a fault with the mains wiring feeding the wall sockets (possibly due to some sloppy DIY work), again the field generated by the cables will be virtually non-existent. In the UK we still use the "ring" circuits for the mains wiring. In Europe and elsewhere, "radial" circuits, or "tree and branch" circuits are used, and these force the return current to travel back down the same piece of cable, hence the fields will be self-cancelling. In the UK's ring system, the wires are laid out in a circle with both the Live and Neutral wires starting and finishing at the consumer unit. This means that the current used from a socket outlet has two possible ways to flow to and from the consumer unit. Currents many not flow equally both ways around the ring, so the magnetic fields produced may not cancel, and the cables then radiate these higher magnetic fields into the room and the adjacent rooms.

At every socket on the ring two cables are joined. A small difference in the impedance back each way to the consumer unit around the loop will cause a problem almost as bad as a poor connection. In the worse case, which is surprisingly common, a Line or Neutral actually gets disconnected (often as a result of incompetant DIY) and this effectively results in a single turn transformer loop. When a significant load is applied, the magnetic field in the rooms inside the ring can rise to many microTesla. To put this into context in the UK the average for the mains cable feeder into the house is 0.04 microTesla. For detached houses set back from the road it is about 0.02uT. Flats and terraced houses right up to the pavement have higher fields, however if they are about 0.1uT then an external supply fault should be suspected.

Consider a ring running around a 3 x 3 metre room supporting a total load of 2A (i.e. 450W). The radiated magnetic field 60cm into the room will be 0.01uT, falling to 0.001uT one metre in. Whereas if both L and N wires were to become disconnected (worse case scenario) the respective magnetic fields would be 0.6uT and 1.5uT.


Another source of unwanted magnetic fields (at frequencies higher than 50Hz) are those generated by 'wall warts'. Commonly used to charge mobile phones (but sometimes audio items), these device can emit high fields nearby, and also inject noise back into the mains system. If not in use they should unplugged, or at least switched off at the socket.

[Jimbo]

Yes, the interference can only be caused by near adjacent cables, but to have an effect the screening of the audio cable would have to be poor. Also since in a mains cable the L and N wires are adjacent and run very close together within the outer sheath, separated by their own insulation, the fields they generate are almost mutually cancelling.

Unless there is a fault with the mains wiring feeding the wall sockets (possibly due to some sloppy DIY work), again the field generated by the cables will be virtually non-existent. In the UK we still use the "ring" circuits for the mains wiring. In Europe and elsewhere, "radial" circuits, or "tree and branch" circuits are used, and these force the return current to travel back down the same piece of cable, hence the fields will be self-cancelling. In the UK's ring system, the wires are laid out in a circle with both the Live and Neutral wires starting and finishing at the consumer unit. This means that the current used from a socket outlet has two possible ways to flow to and from the consumer unit. Currents many not flow equally both ways around the ring, so the magnetic fields produced may not cancel, and the cables then radiate these higher magnetic fields into the room and the adjacent rooms.

At every socket on the ring two cables are joined. A small difference in the impedance back each way to the consumer unit around the loop will cause a problem almost as bad as a poor connection. In the worse case, which is surprisingly common, a Line or Neutral actually gets disconnected (often as a result of incompetant DIY) and this effectively results in a single turn transformer loop. When a significant load is applied, the magnetic field in the rooms inside the ring can rise to many microTesla. To put this into context in the UK the average for the mains cable feeder into the house is 0.04 microTesla. For detached houses set back from the road it is about 0.02uT. Flats and terraced houses right up to the pavement have higher fields, however if they are about 0.1uT then an external supply fault should be suspected.

Consider a ring running around a 3 x 3 metre room supporting a total load of 2A (i.e. 450W). The radiated magnetic field 60cm into the room will be 0.01uT, falling to 0.001uT one metre in. Whereas if both L and N wires were to become disconnected (worse case scenario) the respective magnetic fields would be 0.6uT and 1.5uT.


Another source of unwanted magnetic fields (at frequencies higher than 50Hz) are those generated by 'wall warts'. Commonly used to charge mobile phones (but sometimes audio items), these device can emit high fields nearby, and also inject noise back into the mains system. If not in use they should unplugged, or at least switched off at the socket.

Great advice and knowledge there Barry. I had an earth wire drop out of a socket recently which was picked up on an electrical test. I have always understood SMPS generated lots of unwanted magnetic fields which can be injected back into the system and not great for powering small DACs or any other audio device really unless they are specially designed so as not to interfere with the electronics they are strapped too?

[Gazjam]

QUOTE=Macca;1380646]I have the power cables all down one side, well away from the signals. No wall-touching here!

[/QUOTE]


Martin,

Is your wall very small, or just far away
(Measurement Protocol has to be adhered to...)

[Jimbo]

Well after my cable deliberations I have stumbled across another strange phenomena tonight with regards plug sockets.

I usually plug my Linear Power supply into the left hand side of a double socket I have spare for use with my system. The LPS has two 5v outputs which feed power separately to a DAC and a DDC which in turn is connected to my MacBook laptop which runs on battery. Audirvana shuts down all the noise in the laptop and re routes the digital info and sprinkles magic on it on the way out to the DDC.


Ok enough of that and now to the crux of the matter. Tonight having plugged the LPS into the right hand side of the socket rather than the left I have had an astonishing uplift in both dynamics and a far more holographic soundstage.


WHY?

[Firebottle]

Everything matters, but who knows?

Perhaps the swiping of the contacts changing the conductivity, but who knows?