The Cables/Power Supplies Discussions

[denom]

Starting a new thread which can continue the dedicated discussion that was had here
http://www.hifivision.com/audio-video-cables/47036-power-cables-am-bewildered-25.html

Lets keep this thread as relevant to the topics discussed as possible as that way all of us can learn about cables, power supplies & other allied components. I hope we all can pick Kanwar's & other knowledgeable FM's brains on these topics & benefit from their knowledge. Lets keep the snake oil away as much as possible

At the end of the day, we must learn why certain companies give us crappy excuses & continue to give us sugar coated BS by saying that you may lose 'musical contact' if you eradicate hum etc...

Kanwar, pls do reply to these queries as noted below:

Good would mean:
1) wire gauge is sufficient to supply the required current without heating up. If a cable heats up, it is a sure sign that it is carrying more current than what it ought to be carrying (assuming that there isn't sparking anywhere - which is infinitely more dangerous). Prolonged heat leads to gradual breakdown of the insulation. In extreme cases, it can lead to fire.

If you are using a power cord that came with your computer, you can check the power ratings of your computer. Let's assume 400 Watts is the SMPS rating. So the cable will be safe for 400 W. Now, check how much power is used by the device which this power cord is powering. If it's below 400W, you ought to be safe. Of course this considers only one parameter (see below points).

2) preferably twisted, for reasons already covered by Kanwar.

3) proper contacts - more than the cable's connector pins per se, the culprit is often the poorly designed contact within the sockets that does not tightly grip the pins. Any looseness in electrical contact leads to current jumping from the source to the nearest conducting body. This is sparking, and very dangerous. Indian 3-pin round pin-sockets standard is very bad in my personal opinion. Flat pins as used in American and British pins are better as the spring action of the socket conductors can have firmer grip than round conductors. Round holes need close tolerances (of both pin and hole) to make proper contacts. More often than not, a tight fit is wanting.

4) preferably shielded, so that it doesn't suffer more induced pollution from radiated emissions which may be present in the surrounding.

I'm not sure that we should take that as a complement hyeah:



Hmmm....

Kanwar? Having decided that size matters, should we worry about that .25 inch of titchy wire inside that fuse?

I never did before, but heck, there is stuff to learn.

I am eagerly waiting for your thoughts for the above two questions. Let's say the minimum criteria for a good cable is what jls001 mentioned (and also being twisted). I am repeating the questions again and trying to put them short and precise.
1. Apart from suppressing the "radiated emi" (and also assuming the cable is good enough to carry the required power and plugs fitting correctly/tightly into the socket), what other benefit does this "band-aid" solution offers for audio components with poorly designed power supply units ?


2. As Santy has asked, what is the difference between a $50 and a $1000 band-aid ?

This thread has been sharing more technical details and so I expect a technical answer as well.

so whats a bad power supply in an equipment?

What about a decent smps
what about a trafo/caps based regulated supply using 78xx or equiv regulators.
what about a trafo/caps based linear supply, with enough caps.

how would you improve the above mentioned supplies so that you dont need a band aid.

 

[denom]

Some queries from me also:

1) Why are SMPS considered noisy/un cool for 'audiophile' grade amps?

2) Why don't tube amps have smps???

 

[prem]

Hi denom

The general belief is smps generates a lot of rf so if its in the vicinity of the system there could be some negatives. I do not know how much of this is true though.

The miniwatt tube amp from HK uses smps.

 

[mowgli80]

I have few questions
1) is the noise in power supply always bad?
2) Is the noise always consistent based in characteristics of wire or is variable based on power characteristics at an instant?
3) Will all the ways to counter it eliminate it completely or to a large extent?
4) Does using multiple levels of cheap extension boxes (I do not think they protect against surge although they do claim) affect the performance?

 

[kanwar]

Let me try:

At the end of the day, we must learn why certain companies give us crappy excuses & continue to give us sugar coated BS by saying that you may lose 'musical contact' if you eradicate hum etc...

Kanwar, pls do reply to these queries as noted below:

Sugar coating is done when the designer lacks the skill-set to innovate something new/out of the box and wants to stick with traditional flawed approaches, some times he himself is not aware of the flaws.

Originally Posted by jls001
Good would mean:
4) preferably shielded, so that it doesn't suffer more induced pollution from radiated emissions which may be present in the surrounding.

Shielding a power cable serves no purpose. If you think by shielding you are protecting the cable from getting induced from external fields then let me tell you, the power cable carries 220V potential and its electrical field is quite large and in order to impose some RFI on it from the surroundings with AIR as a medium you need some KILOWATT level of RFI equipment in your environment which is never the case in homes. Only possible when you are living in the control room of a mobile tower where the RFI ingress is felt in heavy breathing itself[person experience], the Non Ionized Radiation as we refer to it.

Originally Posted by Thad E Ginathom
Kanwar? Having decided that size matters, should we worry about that .25 inch of titchy wire inside that fuse?

It depends on the construction of fuse itself, lot of variable to play such as the welded joints and setting of fuse contacts with the holder itself. A loose fuse will always arc and led to RFI to some extent.

Originally Posted by shanmune
1. Apart from suppressing the "radiated emi" (and also assuming the cable is good enough to carry the required power and plugs fitting correctly/tightly into the socket), what other benefit does this "band-aid" solution offers for audio components with poorly designed power supply units ?

2. As Santy has asked, what is the difference between a $50 and a $1000 band-aid ?

Apart from Radiated RFI, Nothing else then Show off.
^^^
Provided the cable is having a good gauge copper and good terminations + twisting.

If someone is saying "My system is very revealing because it can show the difference between various power cables, Sorry to say but your system is not revealing its actually prone to various flaws inherent in your power supply design + circuit design"

Originally Posted by doors666
so whats a bad power supply in an equipment?

What about a decent smps
what about a trafo/caps based regulated supply using 78xx or equiv regulators.
what about a trafo/caps based linear supply, with enough caps.

how would you improve the above mentioned supplies so that you dont need a band aid.

A bad power supply is[Normal Linear supply in this case] :

1. Badly wound transformer having huge primary to secondary leakage capacitance, so that it can pass RFI in free-flow. Lack of Faraday Shielding.

2. Bad PCB layout, summing of common-mode currents and differential currents is not properly done.

3. Using 78XX regulators what you achieve is very less because the PSRR of these regulators covers only narrow bandwidth, LM317 is much better then it. Worst thing is 79XX and LM337 which are band-aids in the form of negative regulators.

4. High capacitance power supplies are OK but more capacitance then needed is an overkill in itself.

I will come to smps part in next posts.

 

[kanwar]

Some queries from me also:

1) Why are SMPS considered noisy/un cool for 'audiophile' grade amps?

When people with lack of skills in switching power supplies 'Tend' to design them, the noisy thing takes birth and gives bad name to Smps

2) Why don't tube amps have smps???

Some people think using traditional approach is better which in actual is flawed when it comes to tube amp power supply. Tube amps are mostly designed with zero or less negative feedback, which makes them prone to power supply disturbances much more then their SS counterparts. So you end up with having heavy iron chokes to filter HUM out of just some few milli-amperes of current and DHT amps still gives you Humming with high sensitivity speakers.

Hi denom

The general belief is smps generates a lot of rf so if its in the vicinity of the system there could be some negatives. I do not know how much of this is true though.

The miniwatt tube amp from HK uses smps.

Yes Prem,

The general belief..........

Do you know that the medical field equipments[Life Support systems, ECG machines, MRI machines, Lasers] also run on SMPS and their noise critieria and RFI Radiation is much more of a concern then what you can feel in audio domain. Still they are used just because there are ways to design a SMPS with much much less Noise, Radiated EMI and robust reliability.

There is a new family of SMPS which is known as Resonant switching which includes Zero current switching and Zero Voltage switching which not only reduces EMI, RFI Noise pollutions, but actually exceeds the specs which are once dominated by linear supplies. Now its possible to achieve much better specs such as ultra low level noise, Zero Hum, stiff regulation, power factor correction, and so on.

Its sad to see that much of the said smps implementation is mostly in Aeronautical and Medical field. There are even some examples in audio sector as well where resonant switching techniques are applied in the smps for above mentioned features.

Old traditional smps work on what we call Hard Switching. Its RFI inferno by default.

Secondly the PCB layout also matters alot in SMPS designs.

In pro-audio, several companies have adopted to resonant switching for the obvious benefits and features it is providing.

 

[Shivam]

So shielding is useless in power cable and doesn't cause any improvements in the quality, but does the power cable induce any noise in the other line level and speaker cables? Is shielding of power cable useful in this aspect?

 

[kanwar]

I have few questions
1) is the noise in power supply always bad?

Bad for Preamp,phono stages, not much an issue for power amps

2) Is the noise always consistent based in characteristics of wire or is variable based on power characteristics at an instant?

Lots of variables to play with.... Wiring geometry, pcb layout, power waveform contamination and so on

3) Will all the ways to counter it eliminate it completely or to a large extent?

Elimination is better word to use when power supplies are designed brilliantly


4) Does using multiple levels of cheap extension boxes (I do not think they protect against surge although they do claim) affect the performance?

Again depends on the implementation, if cheaply done then yes it will degrade the performance

Overall its the design skills which matter and access to proper tools for testing it.

 

[kanwar]

So shielding is useless in power cable and doesn't cause any improvements in the quality, but does the power cable induce any noise in the other line level and speaker cables? Is shielding of power cable useful in this aspect?

No, because the shielding is usually attached to earth termination with zero potential and in that way you are actually contaminating the earth.

 

[prem]

Thanks Kanwar for the clarification.

 

[keith_correa]

There is a new family of SMPS which is known as Resonant switching which includes Zero current switching and Zero Voltage switching which not only reduces EMI, RFI Noise pollutions, but actually exceeds the specs which are once dominated by linear supplies. Now its possible to achieve much better specs such as ultra low level noise, Zero Hum, stiff regulation, power factor correction, and so on.

Its sad to see that much of the said smps implementation is mostly in Aeronautical and Medical field. There are even some examples in audio sector as well where resonant switching techniques are applied in the smps for above mentioned features.

Like this?

More here

 

[kanwar]

Like this?

Yup the LLC resonant converter , but the implementation is rather cheap, especially the EMI filter stage and PCB layout and absence of PFC.

 

[kanwar]

Check this link

 

[oglio]

Guys, I have a questions connected to the topic a bit, I think.
My laptop's power supply just fell down from the height of my desk. And it doesn't work, clearly. Three different shop assistants told me it's virtually impossible to stop working. And yet... What's going on? Can it be the power supply?

 

[kanwar]

Oglio,
Your laptop working with different charger?

 

[keith_correa]

So where can we get our hands [in India] on an SMPS with LLC resonant converter topology and having an EMI filter stage & PFC? Anyone know?

 

[denom]

So where can we get our hands [in India] on an SMPS with LLC resonant converter topology and having an EMI filter stage & PFC? Anyone know?

Zypher labs for sure

Advanced Class-D Amplification | Switching Power Fanatics

 

[oglio]

Oglio,
Your laptop working with different charger?

Yup, it works. I had to buy another one, but they got me really upset and concerned if it was just a coincidence and my laptop died.

I bought a Tracer power supply with 12 different plugs and adjustible voltage.

 

[keith_correa]

Zypher labs for sure

Advanced Class-D Amplification | Switching Power Fanatics

I can hear the sound of silence

 

[denom]

I can hear the sound of silence

You know whom to contact, dunno why you are so 'Silent' now