shielding for AC (power, audio)?

[sandyk]

6 hours ago, numlog said:

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

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

[sandyk]

43 minutes ago, audiventory said:

Resume:

Thus twisted pair defend cables by constant electro magnetic field that don't generate current in the cables already.

So there is nonexistent issue is fixed.

 

DC cables can have varying voltages in them due to instantaneous load requirements, especially with digital with it's fast rise and fall times.

This also applies to USB cables where it is best to screen the D+ and D- SEPARATELY form +5V and 0 volts to prevent induced voltages into the data pair, DESPITE it being a supposedly twisted pair.

 

There was a good explanation by John Swenson about this issue , linked to in the 3rd post on this page.

[sandyk]

3 minutes 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.

Same rules apply for AC cables as far as signal cables are concerned, the garbage stays inside the confines of the screen.

I'm fanatical about avoiding coupling from AC cables to signal cables that can run parallel to each other , so all my AC cables for audio equipment are shielded types with the shield connected to ground (earth) at both ends. With AC cables mixing with small signals in close proximity behind the equipment rack, there's always a chance that a signal cable will receive a spike some day.

 

 Likewise. However, I don't feel the need for shielded A.C. mains cables, and try to keep mains cables well separated from my double screened interconnects, crossing them at 90 degrees wherever possible.

[sandyk]

51 minutes ago, audiventory said:

Also ferrite rings are set at cables to absorbtion of interference energy

 

This may be fine for printer cables, but usually NOT a good idea for high speed USB

51 minutes ago, audiventory said:

However, first way to solve it are coils and capacitors, connected into DC circuits.

 

I do not agree with that. I prefer to keep the output impedance of the power supply as low as possible, and the DC cables as short as possible, and with as low a resistance as possible, even if that means boring out the end of the D.C. connector a little if needed to accommodate heavier gauge copper wire. Add to that the John Swenson mods if possible without making the cable too stiff.

[sandyk]

6 hours ago, audiventory said:

For DC capacitors and coils are transparent.

 

 No they aren't transparent .

With DC , filter capacitors, their type (Low ESR etc.) and value help to determine how an Analogue or even a Digital  component sounds. A series inductance changes (increases) the Power supply's output impedance which again determines to some extent how an analogue component especially will sound.

 At the component end of a DC  supply, there will always also be some type of additional parallel capacitor across it's D.C. input. This also helps to determine how the component will sound, because every power supply does have inductance in it's output leads as well as some amount of output impedance.

NO PSU is perfect !

[sandyk]

7 hours ago, numlog said:

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.

 

 Unfortunately, the more twists in the cable the less flexible it becomes .

[sandyk]

Audiventory

Please stop spouting irrelevant Technical stuff to both numlog and myself and treating us both as coming from completely non technical backgrounds  .

I am not a newbie in this area, and I do have a reasonable background in electronics , partly due to 43 years in Telstra where I was a Principal Telecommunications Technical Officer with 43 years experience, and >60 years as a DIY Electronics hobbyist, so please get into the practical side of things, or is your experience limited to mainly as a Software person, and we are having Language related problems here ? 

Quote

 Coil have almost zero resistance for DC. By Ohm law is is equivalent that there is nothing too.

 

That depends entirely on the amount of inductance of the coil, with designs such as in some PSU designs from John Swenson using inductors of 10mH. 

 

Quote

To compensate long term deviations, active electronical circuits (stabilizer) are used.

I have attached a copy of an  active electronic stabilizer that I have further developed (and use) from an original design by the late John Linsley Hood. It not only has a capacitance multiplier section, (around 2 FARADS in my version) ) but it also has active cancellation of ripple to WAY past 300KHZ.

 The original circuit was only published ** with a current limit of 100mA, but this version is capable of higher performance to > 2Amps in either polarity. For improved performance at voltages as low as +3.3V and +5V, the 10K resistor has been replaced by a 1.4mA Current Regulating Diode.

Alex

 

** Electronics Today International April 1994

[sandyk]

47 minutes ago, audiventory said:

I don't like discuss with emotional/non-technical arguments. If you want, I will stop answer to you posts in this topic.

Please do.

You are contributing nothing of practical value to this thread .

 

Quote

If you practically got  resistance R difference for coils with different L, it is wire length and diameter matter only, not inductance.

 

DUH !

 

 Do you REALLY think that I don't know those formulas and how to use them ?

 The 10mH choke that I mentioned previously has  a DC resistance of 160mOhms and is rated to 5A. Yes, there is a voltage drop across It when current is drawn through it , and of course the wire length and diameter of the wire

matters, as well as whether it is air wound, or wound on a ferrite material.

 

 BTW,  the formula is XL=2*PI*f*L

 

[sandyk]

16 minutes ago, audiventory said:

DC voltage drop don't depend on ferrite or air there.

 

DC and AC voltage drops are different there.

 It does, because for the same value of inductance in larger values you need to use more turns of wire with an air core, hence extra DC resistance.

 Please take your theoretical nit picking to a thread where it may be appreciated !

 You have already managed to derail this thread .

[sandyk]

Yuri

 Are you using Google to translate ?

It appears that we DO have a language difference problem here as I suggested in an  earlier reply. .

 

Alex