Strange Forest of Noise with Linear PSU

[xrk971]

What you call "forest of noise" is more a "comb of 60Hz harmonics". The "forest of noise" is similar and in the region of -130dB in both cases.
This is not related to smps or linear supply, but to grounding the secondary circuit. I assume your smps is grounded, your linear transformer not. In that case you compare apples to peaches.

If you had read the thread or at least post 1 carefully you will see it is the same exact grounding scheme. The two SMPS are actually not grounded themselves. But the PSU they feed is grounded per the diagram. So only difference was source of power.

 

[29285]

If you had read the thread or at least post 1 carefully you will see it is the same exact grounding scheme. The two SMPS are actually not grounded themselves. But the PSU they feed is grounded per the diagram. So only difference was source of power.

If you had looked carefully at your plots you would have sees that the difference it is not general (white) noise but the harmonics of 60Hz.

 

[jan.didden]

I just ran across some of these FFTs of tomchr's LM3886DR with proper Power86 PSU and Antek 200w 22vac trafo. The forest of noise is surprisingly similar and very low level but nonetheless still there and not flat dead silent like what I like to achieve and can achieve when using SMPS supplies. Interesting how so many people have the perception that SMPS are noisier than linear supplies.

This is also my exprience. I was pleasantly surprised when I designed my low power SilentSwitcher that it is absolutely dead silent despite being driven by a switcher. Counter-intuitive.

Jan

 

[xrk971]

If you had looked carefully at your plots you would have sees that the difference it is not general (white) noise but the harmonics of 60Hz.

Did I ever call it white noise? We all were talking about harmonics from the trafo - perhaps saturation, but distinct peaks on an FFT are never white noise.

 

[xrk971]

This is also my exprience. I was pleasantly surprised when I designed my low power SilentSwitcher that it is absolutely dead silent despite being driven by a switcher. Counter-intuitive.

Jan

Hi Jan Didden,
I have admired all of your proejcts, and so much would love to have one of your silent switchers. Saw the video and see how handy it is. For now, I resort to making 10:1 resistor dividers to drop the voltage across my power resistor load before taking it into the ADC input. Is your SilentSwitcher available as a kit or only fully-built?
Cheers,
X

 

[29285]

Did I ever call it white noise? We all were talking about harmonics from the trafo - perhaps saturation, but distinct peaks on an FFT are never white noise.

It was the "noise forest" you were talking of - for me this is hum with its harmonics. Maybe noise in the German language has (or had in the past) a more specific meaning than in english language.

 

[jan.didden]

Hi Jan Didden,
I have admired all of your proejcts, and so much would love to have one of your silent switchers. Saw the video and see how handy it is. For now, I resort to making 10:1 resistor dividers to drop the voltage across my power resistor load before taking it into the ADC input. Is your SilentSwitcher available as a kit or only fully-built?
Cheers,
X

Only fully build and tested. Some of those chips like the regulators are pretty much impossible to home-solder unless you have a full-blown stencil and IR oven line.

BTW For those who want to support diyaudio, the SilentSwitcher is now also in the diyaudio store.

Jan

 

[xrk971]

Only fully build and tested. Some of those chips like the regulators are pretty much impossible to home-solder unless you have a full-blown stencil and IR oven line.

BTW For those who want to support diyaudio, the SilentSwitcher is now also in the diyaudio store.

Jan

I understand, thanks for pointing out the DIYAudio store option...

https://diyaudiostore.com/collections/kits/products/linear-audio-silent-switcher

Thanks.
X