atomicbob's SMPS Noise Nuke+ technical measurements

atomicbob’s Noise Nuke+™ technical measurements

Prologue
If you are unfamiliar with power supply or low level noise measurements please review the following select papers:

https://download.tek.com/document/55W_29828_0_HR_letter.pdf
https://www.analog.com/media/en/technical-documentation/application-notes/an124f.pdf

The data presented were collected as follows:
1. PrismSound dScope III audio analyzer
2. Keysight 34465A DMM
3. Picoscope 5243B oscilloscope
4. Tektronix ADA400A differential probe with 1103 power supply
5. Newtons4th LP01 laboratory amplifier, x1 gain, AC coupling, 1MHz bandwidth
6. Custom 200 ohm test load used for measurements
7. dScope analyzer sample rate 192 KHz unless otherwise noted
8. -20dBu level used for testing unless otherwise noted
9. ADA400A set for 100x gain, AC coupling
10. Shielded signal RG179 signal cables
11. Shielded 14AWG and 16AWG power cables
12. ESD, EMI/RFI controlled lab bench and workspace

Noise Nuke+™ is a scaled up version of the original Noise Nuke™
https://www.superbestaudiofriends.o...ise-nuke-for-hp-amps-with-external-smps.5142/

The original version is a cost effective way to greatly reduce noise from the SMPS provided with many audio devices.
Noise Nuke+ pushes the envelope to experiment with what is possible.

This is in no way cost effective nor is it advised for anyone except experienced DIYers.

The capacitor can store significant joules of energy.
At 36V approximately 65 J are available when the output is switched on. There is a small inductor to limit peak inrush current but depending on device equivalent resistance and capacitance, device power switches and electronic switches could be damaged, destroyed, or vaporized. EE knowledge is required.

I am not responsible for any such damage. Proceed at your own risk.



Noise Nuke+ is a much larger version of the original Noise Nuke.
Here are the principal components:
1) 15 mH 4A choke
2) 0.1 Farad 63Vdc capacitor



Point to point wiring in a large aluminum box which provides E field shielding.
Note additional components to original design:
1) 1 uF 100V film bypass capacitor across the big electrolytic
2) 47 uH 5A inductor to limit inrush current to device when output is switched on
3) 20A 250V output switch to be used instead of power switch on device



Front view. Input on right. Output on left next to output switch.



Test load comprising of
1) 200R 50W load resistor
2) 47uF 63V ultra low ESR electrolytic capacitor
3) 1 uF 275V film bypass capacitor



Test setup to measure power supply residual noise on Noise Nuke+ output with test load connected. Textronix ADA400A probe and 1103 probe power supply
Note test setup spacing away from probe PS and lab bench minimizing EMI / RFI



Newtons4th LP01 lab power amplifier which enables dScope signal generator to drive the extremely low 250 mOhm impedance of the Noise Nuke+.
1 MHz bandwidth 0.7A continuous output.



Simulation of Noise Nuke+ performance.
Greater than 40 dB attenuation at 50 Hz and above.



Actual performance measured attenuation of 42.5 dB at 50 Hz and 45 dB at 60 Hz.
Very good correlation between simulation and measured performance.
Below 20 Hz measured performance differs from simulation due to high pass filter in the laboratory amplifier.



Above 1 KHz simulated performance 90 to 110 dB attenuation.
This will be difficult to measure real time due to the combined measurement system constraints:

1) low ESR of 250 mOhms requires high drive current

2) 77.5 mVrms source level used for testing to keep current well within lab amp limits
77.5mV/250mOhms=310mA, about 44% of lab amp capability

3) 77.5 mVrms is -20 dBu, dScope Continuous Time detector noise floor is approximately -90 to -100 dBu

4) measurements will be limited to -70 or -80 dB relative to source of -20 dBu.



dScope + LP01 amp to Noise Nuke+
Sweep results show approximately -65 to -70 dB relative to -20 dBu signal input
-90 dBu level is approximately 25 uV
Difference as expected due to measurement system constraints

 

Keysight 34465A DMM testing with MeanWell MW GST25A05 5V 25W SMPS into
1) test load
2) Noise Nuke+ with test load



3.35 mVrms residual noise measured on Keysight 34465A DMM



Noise Nuke+ attenuates residual noise below measurement threshold of Keysight 34465A DMM



Tektronix ADA400A probe + Picoscope 5243b time domain measurement of SMPS + test load

3.36 mVrms observed
14.1 mVpp observed



Tektronix ADA400A probe + Picoscope 5243b time domain measurement of SMPS + Noise Nuke+ + test load

6.29 uVrms observed
57.4 uVpp observed

significant real world power supply noise reduction



Spectrum measurements are very high resolution 262144 point transforms with bandwidth to 100 KHz.
Averages are between 45 ~ 60 minutes

Note SMPS + test load has 1.55 mV spectral components at 474 and 948 Hz
60 Hz spectral component is at 18 uV
Residual noise floor appears to be below -117 dBu or approximately 1.1 uV




Spectrum measurements are very high resolution 262144 point transforms with bandwidth to 100 KHz.
Averages are between 45 ~ 60 minutes

SMPS + Noise Nuke+ + test load spectral components are below 483 nV
60 Hz spectral component is below 483 nV
Residual noise floor appears to be below -153.7 dBu or approximately 16 nV

The above results are both impressive and difficult to prove.
Measuring in the nanovolt range is challenging. Everything matters.
Shielded AC power cords.
Shielded DC power and signal cables.
Shielded components and test load.
Spacing of Device Under Test from sources of magnetic induction (power transformers.)
Appropriate grounding of enclosures and test equipment
Patience for very long averaging of 262144 point FFTs



Circuit diagram of Noise Nuke+ from IN to Out



Bill of Materials for Noise Nuke+

The original atomicbob Noise Nuke is highly recommended as a cost effective way to lower SMPS noise.

This project was an experiment to observe results of a much larger LC filter.
It is not recommended, except for experienced DIYers. The capacitor can store significant joules of energy
.
At 36V approximately 65 J are available when the output is switched on. There is a small inductor to limit peak inrush current but depending on device equivalent resistance and capacitance, device power switches and electronic switches could be damaged, destroyed, or vaporized.

I am not responsible for any such damage. Proceed at your own risk.

 

reserved for additions or corrections