Do you need AC Noise Filtering For Your Audio Devices?

[amirm]

Short video on the fact that most audio gear already has noise and surge protection in them obviating the need to have them externally.

Amazon basics amplifier teardown: https://www.audiosciencereview.com/...azon-basics-80-watt-amplifier-teardown.20945/

 

[pma]

And if there is a linear power supply with transformer, rectifier and capacitor bank filter, rectifier current impulses have so wide spectrum and create so much EMI noise inside the audio component that any filter before the power line input is close to useless.

 

[respice finem]

Thank you, this confirms what I'm thinking about it - two "loose thoughts" however:
1: One can hardly buy a power strip (at least here in Germany) with 8-10 sockets without a "filter"/surge protector, at least I haven't come across one in years
2: One justification for these would IMHO be, if something should go "up in smoke" during a surge, than better the filter before the attached components than those in the components themselves.
Whether that would work is another question...

 

[amirm]

1: One can hardly buy a power strip (at least here in Germany) with 8-10 sockets without a "filter"/surge protector, at least I haven't come across one in years

They are extremely common and available everywhere.

2: One justification for these would IMHO be, if something should go "up in smoke" during a surge, than better the filter before the attached components than those in the components themselves.

Whichever has a lower ceiling will catch the surge first. In that case, you don't know if that is the power strip or the protection inside the device.

Anyway, most of my focus here was on audio performance, and not safety. There are people out there saying to buy power cables, etc. that are supposed to filter RF, not realizing that RF filtering is already inside the audio device.

 

[respice finem]

OK, from the snake oil perspective they don't make much sense, but having the simple ones bought with the average power strip is not wrong in itself I guess. Anyway, so far I was lucky, where I live we have 2-3 power outages each year, but no voltage surges and such (says my PC UPS), the area is calm in terms of thunderstorms etc.

 

[Doodski]

OK, from the snake oil perspective they don't make much sense, but having the simple ones bought with the average power strip is not wrong in itself I guess. Anyway, so far I was lucky, where I live we have 2-3 power outages each year, but no voltage surges and such (says my PC UPS), the area is calm in terms of thunderstorms etc.

What a great idea. A PC PWM power supply with USB connection that monitors the mains power. The PC geeks would be all over that. I would.

 

[respice finem]

You can have it for your PC, with at least the APC UPSes - but... the AC they generate is not what the audiophiles would like to see. And, last but not least, a UPS is never really silent, at least the ones I've used.
There are solutions for monitoring only, but the prices are on the high side: https://www.amazon.com/Powertronics-Probe-100-Power-Monitor/dp/B00AYRLH24

 

[Doodski]

@amirm a couple of minutes ago I made my annual donation for website bandwidth. You'll see it in your mail or wherever soon.

 

[ksip2021]

This amplifier looks great but It's better to have some measurements on the conducted and radiated EMI emissions. Perhaps a LISN is required for measuring AC noise under such SMPS based unit.

 

[restorer-john]

Not sure if I mentioned this before in the Onyko AVR teardown, but that capacitor that was partially unsoldered has suffered what most of those resin potted caps undergo. The resin surface cracks (notice the cracks in your pic), moisture in the air gets in, and they explode.

Rifa is the most common brand IME that explode, but they all do it.

Here's another:

A huge proportion of kitchen appliances used such caps over the switches/motors etc and sadly, when they go bang, most of the appliances get thrown out when all it was is a dead suppression cap. Even my mum had one go off in her kitchen with a 20 year Kenwood Chef stand mixer. Gunshot sound, followed by smoke while the mixer was working. Scared her half to death, until I told her it was just a cap.

 

[respice finem]

Planned obsolescence? It wouldn't cost an arm and a leg to seal these properly.

 

[Doodski]

Not usre if I mentioned this before in the Onyko AVR teardown, but that capacitor that was partially unsoldered has suffered what most of those resin potted caps undergo. The resin surface cracks (notice the cracks in your pic), moisture in the air gets in, and they explode.

View attachment 116753

Rifa is the most common brand IME that explode, but they all do it.

Here's another:
View attachment 116754

A huge proportion of kitchen appliances used such caps over the switches/motors etc and sadly, when they go bang, most of the appliances get thrown out when all it was is a dead suppression cap. Even my mum had one go off in her kitchen with a 20 year Kenwood Chef stand mixer. Gunshot sound, followed by smoke while the mixer was working. Scared her half to death, until I told her it was just a cap.

Where on Earth do you learn this stuff @restorer-john ? Sigh* The stuff you come up with.

 

[Feargal]

You can have it for your PC, with at least the APC UPSes - but... the AC they generate is not what the audiophiles would like to see. And, last but not least, a UPS is never really silent, at least the ones I've used.
There are some for monitoring only, but the prices are on the high side: https://www.amazon.com/Powertronics-Probe-100-Power-Monitor/dp/B00AYRLH24

As an aside, about 5 years ago I had an APC UPS, not on audio gear but on a home NAS and a few other things. One day I had the electrician in to certify the wiring, and he noticed something on a particular circuit seemed to be close to tripping one of the residual current fuses in the distribution board. After much searching, tightening up mains socket wiring etc., we traced it to the UPS. The battery had gone in it, and for some reason it was leaking live to neutral or earth. Not a great design feature.

 

[respice finem]

My UPS batteries tend to last 4-5 years, then they don't pass the self test any more and need replacement. If a leakage would happen, I hope in the German wiring scheme (Schuko) it would trigger the fuse immediately. https://en.wikipedia.org/wiki/Schuko

 

[restorer-john]

Planned obsolescence? It wouldn't cost an arm and a leg to seal these properly.

The thing is, they are beautifully sealed/potted when new, and even for many years. Then I think the epoxy/resin- whatever it is, crazes (like perspex). Tiny cracks appear, air gets in, the aluminium reacts and the cap start dissipating more than it would. It gets warm, the aluminium 'roll' expands, cracks the epoxy more and the process accelerates until the dielectric is compromised, it shorts and goes bang.

Where on Earth do you learn this stuff @restorer-john ? Sigh* The stuff you come up with.

They call me CSI John.

First it was the common problem back in the day with turntables where they don't turn off (shorted cap over the arm microswitch) or they make a loud pop through the system (open suppression cap) was where I first saw it. Virtually every vintage table had a bad Rifa (or other similar style) brand cap from all the major manufacturers. Then I realized they were on practically every power switch on Japanese gear made in the 70s-90s. Inside kitchen appliances, over power drill switches, even hair dryer switches.

@amirm often has some really cool details buried in his pictures and videos and I can't help myself.

 

[amirm]

My UPS batteries tend to die a few months after the warranty runs out. Many also sit on the shelf and by the time you get them, some of the life is gone from them.

 

[ksip2021]

Those cracks are very common for vintage Rifa capacitor. This may lead to fatal case if applied as class x/y safety capacitor under poor earthing conditions.

 

[Doodski]

The thing is, they are beautifully sealed/potted when new, and even for many years. Then I think the epoxy/resin- whatever it is, crazes (like perspex). Tiny cracks appear, air gets in, the aluminium reacts and the cap start dissipating more than it would. It gets warm, the aluminium 'roll' expands, cracks the epoxy more and the process accelerates until the dielectric is compromised, it shorts and goes bang.



They call me CSI John.

First it was the common problem back in the day with turntables where they don't turn off (shorted cap over the arm microswitch) or they make a loud pop through the system (open suppression cap) was where I first saw it. Virtually every vintage table had a bad Rifa (or other similar style) brand cap from all the major manufacturers. Then I realized they were on practically every power switch on Japanese gear made in the 70s-90s. Inside kitchen appliances, over power drill switches, even hair dryer switches.

@amirm often has some really cool details buried in his pictures and videos and I can't help myself.

Well.. Keep up the good work!

 

[restorer-john]

Those cracks are very common for vintage Rifa capacitor. This may lead to fatal case if applied as class x/y safety capacitor under poor earthing conditions.

Yes, such caps were nicknamed "Death Caps" when they broke down (short) from active to chassis. More common than people know.

Fortunately, the filter caps on the unit in Amir's video appear to be of excellent quality. There's no doubt the modern X2 caps are superior with their 'self healing' properties, instead of self destructing properties like the ones we are discussing.

 

[Doodski]

Yes, such caps were nicknamed "Death Caps" when they broke down (short) from active to chassis. More common than people know.

I have more experience with high current PWM DC-DC and mechatronics than household AC electronics and I sure see the stuff I that missed when you guys chat this sort of stuff. X-Y safety capacitor stuff simply didn't exist for me.