AC Line Noise

[Ralf11]

Noise on the AC Line is often invoked as being detrimental to the SQ of a DAC, as well as other gear.

 

I happened across this paper recently & thought I'd post it here...

 

https://www.nist.gov/sites/default/files/documents/pml/div684/Propagation_1983.pdf

[sandyk]

On ‎5‎/‎29‎/‎2019 at 8:21 AM, Ralf11 said:

Noise on the AC Line is often invoked as being detrimental to the SQ of a DAC, as well as other gear.

 

I happened across this paper recently & thought I'd post it here...

 

https://www.nist.gov/sites/default/files/documents/pml/div684/Propagation_1983.pdf

 

That report is 36 years old, and from well before the proliferation of noisy SMPS, LED lighting etc.

 These days, much of this interference is radiated not just transported via the A.C. mains supply.

 It even has the potential to virtually wipe out Short Wave reception in many locations these days, as well as non local  AM band reception.

[Ralf11]

ok, sketch this out for me

 

What distance is the PS from the DAC chip, or whatever it will be injecting noise into?

 

Then how long is the power cord?  

 

Any wires crossing or running parallel to each other?

[sandyk]

9 minutes ago, Ralf11 said:

ok, sketch this out for me

 

What distance is the PS from the DAC chip, or whatever it will be injecting noise into?

 

Then how long is the power cord?  

 

Any wires crossing or running parallel to each other?

Even a refrigerator cutting in and out may affect some Audio equipment, especially if the mains earth isn't great.

The original Spark Transmitters could even transmit 1,000s of miles on occasions.

Accidental rectification of this radiated energy can happen with Audio gear ,especially with corroded contacts ,dry joints etc

 It can even come in via the speaker leads and the NFB network.

 The old Analogue VHF TV transmitters were capable of injecting "Frame Buzz" into amplifiers via this method if you lived within a couple of KM from them

[Ralf11]

got any numbers for the distances?

[fas42]

A simple method of evaluating a self designed mains filter, some years ago, was to make a physically bad connection between plug and socket driving a heavy load; that is, severe arcing between the connectors by disconnecting to the precise point where contact was just lost - on a separate circuit from the audio. Without the filter, substantial noise came from the speakers - with, essentially silent.

 

Again, the principle is to apply a severe test to the equipment - if it passes, then real gains have been made.