shielding for AC (power, audio)?

[numlog]

Is it generally a good or bad idea to add passive shielding (no ground) to AC cables?

 

I recall reading adding shielding can sometimes create problems instead of improving things but I did some basic tests on a very short coax RCA cable and felt there could be some potential (alu foil tape then an outer JSSG shield) , its not possible to compare and difference is small so I would like to hear if anyone has experience or advice before continuing. Headphone cable and AC power cords are all over a meter and could be the biggest source of interference in the system

 

Twisted pair wiring for DC cables had great results for me, this wouldnt work the same way with AC would it?

 

[numlog]

2 hours ago, audiventory said:

Twisted pair have result for non-DC only. If DC have pulses, twisted pair can give advantages.

 

Shielding have some theoretical bases for design (grounding lopps, as example). But finally, shielding must be adjusted by measurement tools only.

 

This work is effective, when you adjust full system as single complex, including power and signal cables, boards, cases, etc.

 

Read more information https://samplerateconverter.com/educational/power-conditioner

The advice for DC twist pair was taken from this post and a lot of people are using it:

https://www.computeraudiophile.com/forums/topic/31554-diy-dc-power-cables/

 

it is worth trying and very simple to test.

 

It probably depends on the application too, LT3045 power supply for a DAC is fairly sensitive.

 

I will experiment with AC power and audio twisted pair, if DC had good results then AC must be great!

 

Also I dont agree passive shielding should only be done with measurements, it is harmless, simple and inexpensive process and results in the most extreme are either slightly bad or slightly good (and so far nothing bad has come out of USB style shielding on RCA). when we can establish the good practices almost anyone should be able to achieve good results, giving more power to anyone with some DIY incentive not just those with access to measurement tools and the training needed to use them.

[numlog]

1 hour ago, One and a half said:

I would not place a shield over an existing no shielded AC cable, since a strand may end up in the wrong place.

This happened with the RCA and its metal plugs in the beginning, leaving the shield 5mm or so away from the plug and tight wrapping with a sliver of insulation tape held it in place and forms a barrier, checking for a short between shield and plug ground is pretty easy with a multimeter. not a durable solution but RCAs usually arent moved around much. This would only apply to ungrounded shields

 

For power I agree, wrapping conductive materials around a power cable is a bad idea . 

[numlog]

7 hours ago, audiventory said:

I'm not sure test of effectiveness of noise defending is so simple. There are professional measurement tools, special knowledges and experience are necessary.

 

Some coarse issues may be fixed by ears. But fine tuning demands technical instruments.

what would be involved in fine tuning of a passive shield? say you discover the shield is introducing some of its intereference back into ground through measurements, what physical changes to the shield could be made to address that other than simply removing it?

 

From my experience it can be the opposite, coarse issues can be fixed with measurements but a keen ear is needed for fine tuning,  the goal in the end is for it sound better not measure better. measurements, if done correctly, are always reliable and accurate but ears are not, this is the problem.

 

 

[numlog]

12 hours ago, sandyk said:

Hi Numlog

It's easy enough to find out . Simply get a length of 3 core mains cable, remove the 3 wires from the outer jacket ( the hard part) then  tightly twist them, followed by a layer of heatshrink cable, and then shrinking it with a heat gun, followed by another layer of heatshrink cable to help make up for the thinner outer protective layer.  (3 core mains cables already have a larger radius twist)

Don't forget that twisted pairs are also used in telecommunications cables, from 2 pair to main cables between Telephone Exchanges with  > 1,000 pairs.( Even the 2 pair cables have some  AC. mains rejection properties)

 

Regards

Alex

The power cable for my amp and DAC is 10 AWG fine strand speaker cable pairs soldered to the plug and transformer on each end, its awkward but it has to be used to know if the differences were in the twists and not the cables. I managed about 2 twists per inch with amp cord, it sounds better. The DAC cord should have a bigger impact but to be able judge those differences some time is needed to familiarise with the current sound before making more changes. 

Then there is the PC cord too.

[numlog]

57 minutes ago, audiventory said:

What is passive shield? I know simple shield. It eliminate electromagnetic radiation. Correct connecting shield to ground demands special skills.

 

To conrol of shielding result, oscillogram and spectrum in different system points (power or/and signal wires) are checked.

 

If the shielding eliminate noise or unnecessary oscillations in the system point, then shielding is effective.

 

 

Sound quality have 2 definitions:

1. High fidelity - close to original,

2. Nicer sound - subjective perception; sound enhancing.

 

Real record have distortions in recording and playback.

In case #2 level of distortions is not matter. But all these distortions are estimated. There are special processing (tape, tube, vinyl emulators) exists even.

For case #1, distortions also present. And sound depend on balance of the distortions.

I mean there is no connection to ground or anything with a passive shield , passive is probably the wrong term.

 

The aim is for highest fidelity possible with computer audio. To gauge the most accurate and realistic sound it helps to be familiar with a large and varied selection of suitably* recorded music, again it's not perfect process but benefit of certain changes can always be reevaluated at a later time (after the wow factor wears off).

Some distortions can sound nice but I have only experienced this in analogue stage, for interference/noise/distortion etc. on digital side (PC, DAC) reducing these things always helps, subjectively and objectively.

[numlog]

6 minutes ago, look&listen said:

I agree not good term, but what is correct one? Not sure if are correct terms for audiophile use, but maybe following useful?

Define shield for these purposes - metal/conductive tube covering wires carrying power or signal to protect them from outside interference.

Define suggested wire/cable shield type terms-

 

1. 'Floating' shield - not connected to other circuits (your "passive")

2. 'Connected' shield - one connected at one end (or along length), probably need qualifiers for type of connection.

3. 'Through' shield - one connected at both ends.

 

Maybe people here use these words in future? Use of consistent words helpful to understanding, as attempted in these threads.

 

 

Agree strongly, but recorded & Live music!

floating shield is a good engineering term, free spirit shield would be audiophile grade term