Tombo56, very interesting. I am going to show my ignorance now, but here goes. I do notice some differences between the spectrum with the paper shredder and the spectrum in Post #183 with the 22Ω primary resistors. The spectrum with the shredder shows some ripple along the noise floor, and the slope of the declining noise floor is a bit different from the other spectrum. Could both of these just be due to the higher level of the 50Hz signal, or some other simple explanation?
All I know is that once in a place I used to live I got a LOT of noise through my stereo every time the central heating boiler or the fridge kicked in.
Pretty much everybody involved with HiFI I asked about a remedy for this told me that these things put noise on my AC mains and I need to buy a power conditioner to get rid of it.
People involved with pro-audio (PA or studio) told me those power conditioners do nothing.
As it happens the noise completely stopped once I replaced the last single-ended RCA connection with balanced XLR/TRS connections.
So I assume that yes the boiler and fridge produced interference but it was strictly air-borne and had nothing to do with my AC mains.
Pretty much everybody involved with HiFI I asked about a remedy for this told me that these things put noise on my AC mains and I need to buy a power conditioner to get rid of it.
People involved with pro-audio (PA or studio) told me those power conditioners do nothing.
As it happens the noise completely stopped once I replaced the last single-ended RCA connection with balanced XLR/TRS connections.
So I assume that yes the boiler and fridge produced interference but it was strictly air-borne and had nothing to do with my AC mains.
You are right that there is some difference, but there is a simple explanation for that.
First, there was actually no visible difference that day with shredder turned on or off. I included only measurement with shredder on. First set of measurements was taken on Saturday, when local metal processing industry with heavy welding machines was closed. Elevated LF noise floor is due AC voltage jumping slightly up and down in one second rhythm of welding machines. Pay attention that at very low frequency end, noise floor, on such a bad day is about 10 uV.
Then, consider how much that 10 uV of noise (mind you on test circuit with no input RF filters) can affect power amplifier. 🙂
I’ve made, that day, also a check with oscilloscope to see if there is any visible HF noise riding mains voltage, as was with Shunyata demo. Here are attached 100 frames long secondary voltage waveforms with and without paper shredder working. You can observe mentioned voltage jumping and that there is no visible additional noise. Oscilloscope was in full bandwidth mode.
Attachments
I do not disagree at all with that comment. That level of noise is insignificant. There may be some individuals that claim to hear some effect on their program material, but it is all subjective, so I am not going to ague with them.
I think the more interesting point is that you are able to measure that noise with relatively common equipment that is available to many DIYers. Granted, your location and the types of nearby noise is a worse case scenario. Your thoughts on the possibility that the background noise on your power lines masked any noise produced by the shredder?
Was your equipment differential to start with?
With 100 – 200 $ ADC like Focusrite, Motu, Behringer or any decent sound card and free software, we can enjoy measurement performance that would, 20 years ago, require to spend over 10000 $.
Add the LNA (Low Noise Amplifier) and we can measure to single nV levels. That is simply amazing.
Noise nature is random. It is known that averaged FFT measurement will display that random frequency noise as an elevated noise floor level, as noise peaks are not consistently repeating at exactly the same frequencies over time. AC commutator motor produces noise through electric sparks at the commutator contacts and electrical sparks produce noise over wide frequency span. But nothing is visible at FFT noise floor. Very low frequency noise flor rise was explained previously and is not related to shredder motor. I also checked with oscilloscope, primary and secondary voltages, for any additional random noise peaks riding main voltage, up to 200 MHz.
Reason why there was no strong additional noise, like with Shunyata demo, are mandatory noise suppression filters.
That is the reason why I think that Shunyata example is made up using a modified shredder.
There are no balanced inputs at my measurement equipment.
We definitely shouldn’t care for radio waves riding power wires as those are at the single digit uV levels.
IMO, we should care for any strong noise at audio frequencies and up to above upper frequency response of our audio circuits.
Not all higher frequency noise will be converted to DC. Because of circuit parasitic inductances and capacitances, some HF noise can jump or skip PS rectifiers and capacitors and enter supplied circuits.
It is reasonable to have some RF filters at high quality audio equipment mains power input.
A linear power supply has significant filtering (mostly provided by the transformer itself and the smoothing capacitors), and that usually removes most of the noise that is carried by the mains.
Source of the above information and more: https://sound-au.com/articles/mains-quality.htm
Yes it certainly can depending on the frequency and amplitude of the noise. While any coupling of RFI directly to the equipment from sources outside the room the equipment is actually in is probably not an issue, there are many sources in the immediate environment that can cause problems. Network APs, LED light bulbs and the SMPS's found in just about everything all can lead to a very noisy RF environment. While all such items are theoretically required to be tested and certified against EMI emissions, you can be sure that cheap piece of imported gear has probably not even been tested for basic electrical safety, much less EMI. Point is, there is typically a lot of EMI in any given room and a wire (power or trace on a PCB) is, in addition to it's actual purpose, an antenna. While much of the unwanted signals entering a piece of equipment are filtered out by the input filter (if any) and the following rectification stages, the amount filtered is typically less as the frequency gets higher - and once present in the system they can easily alias down into bands that can cause problems. Also note that this problem is not one that can be addressed by a expensive shielded power cord - when the electrical run may be well over a hundred feet or more of unshielded wire, slapping a shield over the last couple of feet really doesn't accomplish much. A proper EMI filter, preferably internal to the unit but an external can do wonders as well, coupled with a good grounding system can eliminate much of the problems it may cause. Keep in mind, though, that much of the noise may not even be entering through the power system - look at all the wiring also attached, from other inputs to speaker wiring - all antennas. Also to be effectively shielded from external EMI, equipment must be completely enclosed in a well grounded metal shield. As things like connectors and displays are pretty much required, there will always be ways for EMI to enter.
Just a few comments...
Hal
Of course all of the above is, while true, probably never going to be an issue. As long as a certain basic level of care is shown - don't go hanging your AP directly above your equipment and you use decent connecting cables. properly grounded, etc. - any audible problems will be extremely rare. Most commercial grade audio equipment has been tested (technically, it is required to be to get a UL listing) against EMI and can shrug off most of what it will encounter as long as it has been well designed. Note that once someone opens it up and starts swapping parts out it no longer qualifies as "well designed" and moves straight to "experimental." Seriously, I read about people swapping a perfectly good, well behaved NE553x out with a ADI part with a GBW in the 100s of MHZ and they wonder why Things Don't Work (tm) - all of a sudden, that small amount of coupled noise that previously caused no problems now causes R2R oscillations.
You arenot "Rick Miller" at all but a shill trying to inject marketing BS into DIYAudio.
Or "Rick Miller" got a second job, working from home.
NO WAY you are just a random DIYAudio member, "just sharing some wonderful News"
Maybe or maybe not. There is a lot of noise on AC lines, some of it RF. Sometimes it can affect audio equipment. Some power conditioners work quite well and others do virtually nothing useful. The old Monster HTPS 7000 MkII designed by our own Richard Marsh and 1audio (aka Demian Martin) are still some of the best ever, and often available in used form on ebay. Well worth a try IMHO.
How much do you see? I see a knob that can give any number you want. No indication if it is AM broadcast, arc-welder, distant lightning, or paper-shredders.
It does seem to show a lower number on the fatter cord. Showing that filter theory is a practical thing.
OK, and if the AC wave changes the DC voltage changes. If I step-down to 14VAC and get 20V of DC, then the line spikes to 16V, the DC tends to go to 22V.
IMHO it is the audio equipment's job to take "ANY" power we give it (within commercial reason) and not let it bother the owner. However some ears demand power cleaner than the driven snow.
Nice, simple, seductive sounding theory. However, the market for most consumer audio gear tends to be rather cost sensitive. Who will pay an extra $50 or possibly more for really good line filtering with multiple channels of dual back-to-back filtered isolation transformers and well-designed common mode chokes, which the owners may not think they need? Probably not enough people to justify adding anything serious like can be found inside the Monster HTPS 7000 MkII. Even used, those old power conditioners tend to go for around $500 and they are heavy to ship with all the iron inside. At least the schematics were posted by Richard Marsh in one of the Blowtorch threads, and Demian recommended that the MkII is used the version to get.
Does using one affect SQ? IME, unequivocally yes. But I live in an area that has some particular local power quality conditions and RF pickup on the line. Might be different for someone else, probably is different.
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Wrong, you are totally wrong JM, Look at back issues of The Audio Amateur in the mid 1990's, I am in there working together with the great Walt Jung on DIY audio. You are way off base!
I'd be weary of those doing rudimentary tests on small subsets of a system and thinking they are proving or disproving anything. They are missing a lot of interactions within components and sub-components of the whole audio chain.
Measure the whole system at a reasonable output point. For my DAC, I chose its preamp output.
Measure the whole system at a reasonable output point. For my DAC, I chose its preamp output.
I could hear radio on my stereo when I turned it well up but that too disappeared once I switched to balanced connections instead of single-ended.
I take deductions from what I SEE.
Dropping names or rubbing shoulders does not impress me, just SHOW "Rick Miller"s OWN contributions to Audio Science.
You copypaste/link them here.
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