re-simulate the pink noise filter
Per the video mentioned previously:
https://wb9kzy.blogspot.com/2023/12/pink-noodling.html
I retried simulating the pink noise filter with LTspice (using version 8, was using version 4 before):
got this plot:
which is pretty decent, not perfectly linear but there is about 30 db of attenuation over the 10 octaves from 20 to 20,000 Hz. The .meas directive on the schematic yields these measurements:
20hz: v(vout)=(-4.54299dB,-40.1192°) at 20
39hz: v(vout)=(-8.03863dB,-43.6405°) at 39
78hz: v(vout)=(-11.042dB,-41.4805°) at 78
156hz: v(vout)=(-13.5351dB,-42.6511°) at 156
312hz: v(vout)=(-16.6677dB,-45.6843°) at 312
625hz: v(vout)=(-19.9562dB,-44.2764°) at 625
1250hz: v(vout)=(-22.6388dB,-43.1515°) at 1250
2500hz: v(vout)=(-25.5883dB,-45.1273°) at 2500
5000hz: v(vout)=(-28.8253dB,-43.7894°) at 5000
10000hz: v(vout)=(-31.2318dB,-41.6397°) at 10000
20000hz: v(vout)=(-33.3102dB,-47.8667°) at 20000
It still doesn't exactly match the spreadsheet simulation (LTspice in column B and spreadsheet in column C) but LTspice automagically measuring is much easier than trying to read off values from the waveform screen ! The readings are relative to the start at 1 Hz (0 db).
https://wb9kzy.blogspot.com/2023/12/pink-noodling.html
I retried simulating the pink noise filter with LTspice (using version 8, was using version 4 before):
got this plot:
which is pretty decent, not perfectly linear but there is about 30 db of attenuation over the 10 octaves from 20 to 20,000 Hz. The .meas directive on the schematic yields these measurements:
20hz: v(vout)=(-4.54299dB,-40.1192°) at 20
39hz: v(vout)=(-8.03863dB,-43.6405°) at 39
78hz: v(vout)=(-11.042dB,-41.4805°) at 78
156hz: v(vout)=(-13.5351dB,-42.6511°) at 156
312hz: v(vout)=(-16.6677dB,-45.6843°) at 312
625hz: v(vout)=(-19.9562dB,-44.2764°) at 625
1250hz: v(vout)=(-22.6388dB,-43.1515°) at 1250
2500hz: v(vout)=(-25.5883dB,-45.1273°) at 2500
5000hz: v(vout)=(-28.8253dB,-43.7894°) at 5000
10000hz: v(vout)=(-31.2318dB,-41.6397°) at 10000
20000hz: v(vout)=(-33.3102dB,-47.8667°) at 20000
It still doesn't exactly match the spreadsheet simulation (LTspice in column B and spreadsheet in column C) but LTspice automagically measuring is much easier than trying to read off values from the waveform screen ! The readings are relative to the start at 1 Hz (0 db).
Also, whoever wrote LTspice never used a sliderule, 4 digits of precision after the decimal for db measurements and phase ? I kinda doubt the usefulness of those tail-ending numbers :)
Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm
