Impact of AC Distortion & Noise on Audio Equipment

[Xulonn]

Are you having "layering" problems with your stereo that such devices solve? Let's pray not....

No layering problems with music, but my carrot cake layers are 90 degrees out of phase...

 

[pma]

I know 1050Hz aberrations on the mains waveform. I can hear them everyday (and night).

Most probably DSM control again. They used to use 1060 Hz here.

 

[b4nt]

Most probably DSM control again. They used to use 1060 Hz here.

I some time played with common transformators. They could be very transparent. I used them reversed, for fun, feeding them with signals far above 50Hz (between 2K and 5kHz) making them ring, to generate HV. Out of a 220/9V reversed you may get so 2kV.

 

[DualTriode]

Not a reason vast majority of people buy these products.

@amirm ,

If it ain't broke don't fix it.

We could use a definition of what is broken and what needs fixing.

It could be as simple as power supply output impedance affecting the the amplifier SQ.

No amount of power line conditioning will improve a nonzero power supply output impedance. The addition of a power line conditioner could very well make things worse.

Thanks DT

 

[Xulonn]

I have a set of 300B amps. I can hear differences in sound quality at different times of the day. I've always attributed it to noise on the power line.

I have a pair of human ears connected to a human brain. I can hear differences in sound quality at different times of the day. I've always attributed it to noise in my imperfect nervous system - which is a big mess of bioelectric circuits.

 

[MakeMineVinyl]

Very enlightening. One thing I would add however regarding power amplifiers is that the very dirty 'dimmer' AC voltage is likely to generate acoustic noise from a large power transformer in the amplifier. Transformers can be sensitive to things like high DC on the AC mains (from even order distortion), and in the experiments I've conducted, large toroidal transformers absolutely hate things like the step-like waveform from the 'dimmer' simulation.

Though not directly influencing the quality of audio, the acoustic noise can become irritating.

 

[filo97s]

Just posted a link to this article in an audioidiot "hi end" group on Facebook. Just got banned.
I'm proud of this.

 

[Eskamobob1]

Sorry If I missed it, but were ant low impedence loads used? And if no, any plan to test that? Currious to see how that may affect things

 

[amirm]

Sorry If I missed it, but were ant low impedence loads used? And if no, any plan to test that? Currious to see how that may affect things

What is a "low impedance" AC load? Who specs the impedance of any AC load?

Do you mean power factor? If so, I can measure and report back on the three units I tested.

 

[Azathoth]

When I was an audiophool early on in my life I would buy expensive power cables to replace my laptop's, thinking it would improve my fidelity. It was around 100 dollars or so for just a meter. Had custom plugs on it too with gold prongs whatever. I wish I learned about this stuff sooner.

 

[amirm]

@amirm Why is the output only ~1/2 what it should be (compared to the other two devices)? It's still 120VAC, right?

Ah, you noticed that. They are all producing similar voltages. For some reason though, my measurements show half the output for PS audio P300. I tried to troubleshoot the reason but ran out of time. From my quick testing, it may be that it is producing balanced power as I think I measured 60 volts referencing PE ground.

 

[DonH56]

The B&K supply is "only" 300 W so not useful for power amps and really low-impedance loads. As @amirm said, this focuses on line-level'ish components, though could probably run it on some power amps with low output (say 1 W or 5 W) if they do not draw enough to trip OC protection due to in-rush current at turn-on.

I am sure there are outliers that folk will carry on about, but this shows exactly what most of us would expect from a competent supply, especially in a low-level component. PSRR and line noise rejection are very, very high.

Power amps are much worse IME due to unregulated supplies and fairly direct coupling to the output stage, but there is still DC conversion and feedback so I'd not expect much. As @pma's results show, there is measurable added noise, but most likely inaudible. Chances are an amp using a SMPS would exhibit essentially no practical response to line noise.

But we can continue to flog the deceased equine, poor thing.

 

[amirm]

Amir measure differential mode noise , what about common mode noise ?!

Common mode chokes are very common in electronics (usually there for regulatory reasons). In addition, your output, i.e. the speaker, is a differential load. It doesn't care what the signals on the speaker cable are doing relative to safety ground. And of course use of balanced interconnects helps a lot in impact of common mode noise.

Is there a scenario I am not addressing here?

 

[Anthony101]

In my view, a power conditioner is an unnecessary expense and nothing other than a glorified over-priced power bar with fancy lights; another myth from the audiophile world that bites the dust thanks to Amir's enlightening reviews.

 

[b4nt]

Common mode chokes are very common in electronics (usually there for regulatory reasons). In addition, your output, i.e. the speaker, is a differential load. It doesn't care what the signals on the speaker cable are doing relative to safety ground. And of course use of balanced interconnects helps a lot in impact of common mode noise.

Is there a scenario I am not addressing here?

A lot of DACs and audio setups are connected using unbalanced

 

[amirm]

A lot of DACs and audio setups are connected using unbalanced

Anyone using unbalanced RCA is taking chances with ground loops. Adding another box in the middle to generate power or filter it may make things worse or better in those cases. Fortunately such issues are very rare when it comes to audibility. Our hearing sensitivity is very poor in lower frequencies so it takes a lot of mains noise to make it audible.

 

[b4nt]

Anyone using unbalanced RCA is taking chances with ground loops. Adding another box in the middle to generate power or filter it may make things worse or better in those cases. Fortunately such issues are very rare when it comes to audibility. Our hearing sensitivity is very poor in lower frequencies so it takes a lot of mains noise to make it audible.

Not only ground loops, but according to the setup, other noises (like a motor starting up).

Main point being that all those noises are up to very audible. One just needs to switch all his audio units on (like DAC, amp, and PC or Pi). And listen (with no file playing, or at low audio level). If there is nothing audible for a raisonnable long period, there should be nothing to change (motor still may pop in later).

 

[Headchef]

Interestingly I’m in the middle of evaluating a Bp-600 power conditioner and some rather exotic mains leads. I’d have liked to believe that they’re magic snake audiofool oil filled profit generators but they have had a distinct effect on the reproduction. I’m using a class-a (heated triode) amp and to my surprise the addition of the BP-600 is the difference between day time and night time listening. I also have a very dubious mains supply as there are 6 fridges & 1 deep freeze hooked up (along with various other commercial appliance, we have a restaurant). With the Bp-600 plugged in listening to my hifi sounds just like it does a couple of hours after we’ve closed and shut everything off. Better. I’ve not mentioned the manufactures as I’ve no vested interest in promoting using them or not, but I have been surprised by the improvements since being lent the thing.

do you think it’s possible to actually show a short passage of audio from each test and see if there are any effects, preferably one with a varied and broad dynamic range, after all test signals are all well and good but surely there would be value in comparing the audio output, scientifically?

 

[DavidMcRoy]

Lesson: Worry about things that matter.

 

[amirm]

Not only ground loops, but according to the setup, other noises (like a motor starting up).

Again, that is orthogonal to the purpose of this test and article. If you have clearly audible noise/static/etc. sure, try to figure out what is going on and deal with it. I am addressing here problems people don't have, but somehow materialize once they put these devices in their system. They speak of pure fidelity improvements such as lower noise, better bass, imaging, etc.

That aside, what you state is very rare.