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Sources of Noise


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9 hours ago, wanta911 said:

I live right next to a massive casino & multiple hotel complex and initially thought I'd have possible issues with power but have been surprised by how stable my AC supply is when I've measured it and how little affect power conditioners have had in my setup, keeping in mind that I live in a city that is renowned for its inconsistent power supply compared to the rest of the country. I have been told that the casino complex has spent a fortune on some sort of power conditioning.

 

I always thought NYC was the worst

 

but that may be due to the large number of both apts. and of high buck audiophiles (even Brooklyn is a high buck area now)

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ok, summary of things to watch out for in your home

 

- Fluorescent lights (even the 'dead' ones)

- LED lights

- doorbell transformers (good point & I'd never thought of that one)

- heat pumps, refrigerators, a/c units, and other items with electric motors

- wall warts for computers, phone rechargers, cordless vacs & whatever, really any wall warts

- Power Line Communications (there are the small wall warts you plug into an AC outlet to get internet everywhere)

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5 minutes ago, Ralf11 said:

ok, summary of things to watch out for in your home

 

- Fluorescent lights (even the 'dead' ones)

- LED lights

- doorbell transformers (good point & I'd never thought of that one)

- heat pumps, refrigerators, a/c units, and other items with electric motors

- wall warts for computers, phone rechargers, cordless vacs & whatever, really any wall warts

- Power Line Communications (there are the small wall warts you plug into an AC outlet to get internet everywhere)

 

Almost all of these are demonstrably harmless.

 

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1 hour ago, Ralf11 said:

BTW folks - we should probably define common mode, etc. for any newbies

Simply: common mode noise travels across both +|- inputs whether they be cables or AC or DC inputs, whereas differential mode noise is with respect the the voltage difference across the inputs. 

 

All currents need a return path so, for example, when common mode noise enters a circuit along a differential pair, it must return somehow typically along what is called a ground loop. 

 

Google is gives great descriptions.

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1 hour ago, Ralf11 said:

Good!  Now, let's see the demonstration...

 

- Power Line Communications:  No audible or measurable sound difference whether on or off.

 

- LED lights:  No audible or measurable sound difference whether on or off.

 

- Wall warts: No audible or measurable sound difference whether on or off. However, I did have one from Oyen Digital that contaminated my Power Line Communications from my solar panels (think of this as a positive control).  Anyway, that too is easy enough to check (simply unplug them and listen/measure any difference).

 

- Well pump:  This causes a measurable surge and subsequent voltage sag.  I can see some changes in light bulb intensity. However, there is no audible interference (apart from the non-electric noise emitted by the pump).  This one is a rather extreme case, so if the DAC etc is insensitive to a well pump, it should handle much lesser noise from other household motors, pumps, etc.

 

 

 

Things that I have seen that are problematic:

 

- Electric dog sheers on the same circuit as the DAC.  Momentary drop-outs when the motor comes on.

 

- Above=mentioned defective wall-wart.

 

- Dimmer switches. (Not all, but many are problematic).

 

All of these are easily testable and repeatable.

 

 

 

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21 minutes ago, Speedskater said:

The posters on the RFI forum don't think so.

 

Most noise (including RFI) on a power line is inaudible.

 

Again, this is trivially easy to test.

 

In the rare instances in which it is not, one can use a surge protector with filtering (eg Brickwall).

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1 hour ago, Ralf11 said:

BTW folks - we should probably define common mode, etc. for any newbies

It would take a great technical writer to write a understandable & useful to audiophiles description of 'common mode'.  Heck, different electric/electronic fields have very different definitions of 'common mode'.

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8 minutes ago, Speedskater said:

It would take a great technical writer to write a understandable & useful to audiophiles description of 'common mode'.  Heck, different electric/electronic fields have very different definitions of 'common mode'.

 

I don't claim to be a great technical writer, but common mode noise encompassed such topics as "leakage current", as well as good portions  (but not all) of RFI/EMI which many audiophiles seem to be focussed on.

 

Agreed that differential mode noise is much easier to understand, and its also much easier to remove with balanced/differential cables/circuits as well as standard power supply design.

 

Two topics that I've posted on extensively are:

1) use of "ultra" isolation transfomers (e.g. Topaz) as well as balanced power (such as Equi-tech)

2) fiberoptic ethernet

 

Both of these are effective ways to reduce, or in the case of fiber: entirely eliminate, common mode noise transmission, so the take home message is that a good (low interwinding capacitance) isolation transformer can reduce common mode noise on the AC circuit e.g. from your fridge, lights etc etc, and fiber can eliminate common mode noise arising from your NAS, server, switch etc. Of course there are other wrinkles, of course, but those are two simple things.

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18 minutes ago, Ralf11 said:

Thx Bill - I assume these are tests by you in your home?

 

Yes, my house, my DACs, my potential noise-polluters.  YMMV, but in general, it seems to take a lot to degrade audio.

 

I've even listened when we have our generator running during power outages.  If "dirty" power easily degraded digital audio, this should be the ultimate positive control. No issues.

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I've found the same.  I'm in an R-1 zone and suspect you are too (or further out in the moldy boonies).

 

Everything (except for a signal cable - USB) wold have to get past the power transformer too.  However, I do not have measurements or characterizations of the attenuation thru (or parasitically "around") a DC's power transformer...

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3 hours ago, Ralf11 said:

really any wall warts

 

Transformer based AC or DC wallwarts should not be of any real concern.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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50 minutes ago, Ralf11 said:

the transformer-only wall warts shouldn't be a problem - the question is whether any of them have active devices inside for regulation, hence my admonition to regard them with suspicion 

Just a clarification here. In the 'past' some wall warts were a classic linear design, with transformer, rectifier caps and a regulation circuit that was typically a simple LM3xx. Due to the size and heat dissipation, the wall wart's capability was small to modest. If anything, the common mode noise 'could' leak through the heatsink and onto ground from the regulator, but that garbage was a mountain less than switch modes with their rotten X capacitor. 

After all, 80% of preamps use the same topology, sometimes with discrete devices but achieving the same purpose of flat DC. 

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You can  also still obtain AC wallwarts of up to 24VAC at 2A locally from places such as Wagner Electronics., as well as the lower current DC voltage types . (typically to 350mA.)

Gary

 

Another source of noise can be transformers buzzing annoyingly loudly due to due to DC offset of the A.C. mains supply.

 

https://sound-au.com/articles/xfmr-dc.htm

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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8 hours ago, Speedskater said:

It would take a great technical writer to write a understandable & useful to audiophiles description of 'common mode'.  Heck, different electric/electronic fields have very different definitions of 'common mode'.

Perhaps the definitions are lacking or adaptations into different areas are too broad? For example confusion with conducted emissions?

 

For EMC compliance, differential and common mode is readily explained such as this example from Wurth. For common mode noise to complete the circuit, parasitic capacitance forms part of that circuit when the switching device like a transistor. A transistor especially when placed on a grounded (to earth) heatsink can readily transfer common mode noise that exist in other parts of the circuit (or its own). Dependence on the circuit can also cause drama with noise propagation

 

flyback_example_crop_res18.png Differential mode

 

flyback_2_crop_res18.png Common mode

A simpler drawing is from Murata in the pdf. 

Murata Differential and common mode noise.pdf

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I made another change, but without a lot of work I can't tell whether I can hear an improvement.  I have all of the audio stuff on a dedicated, 20 amp circuit.  (I also separate the DAC and analogue components with a filter, but they are on the same circuit.)  I have all of the conventional wall-wart type power supplies on a different household circuit.

 

I'm not sure that this really makes any difference, but the wires were already in place, so I figured I had little to lose.

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Pretty easy to tell if a plug-in supply is causing issues - simply play a recording which is marginal in its perceived SQ, for you; and then plug the wall wart into a socket adjacent to those of the audio gear; firstly have the supply idle, and next actively delivering to a load. Can one hear any variation whatsoever, for better or worse, in the replay sound, for these differences in the environment? If yes, then the rig is sensitive to mains noise - which means that there's room for improvement; either go to greater lengths to isolate the playback chain, or improve the noise rejection internally, of the components.

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8 hours ago, wgscott said:

I made another change, but without a lot of work I can't tell whether I can hear an improvement.  I have all of the audio stuff on a dedicated, 20 amp circuit.  (I also separate the DAC and analogue components with a filter, but they are on the same circuit.)  I have all of the conventional wall-wart type power supplies on a different household circuit.

 

I'm not sure that this really makes any difference, but the wires were already in place, so I figured I had little to lose.

 

I did the same thing - you "lose" about 5 minutes of effort...

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