Noise Generator on ER-PROTO-01

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ER-PROTO-01 NOISE P1080751-720px.jpg

Features

Noise Generator

  • Credit Moritz Klein's Designing a white, pink & blue noise generator from scratch design

  • Noise Generator

Moritz noise.PNG

  • White/Pink/Blue noise

Moritz WHITE PINK BLUE.PNG

  • High Pass Filter (Blue Noise)

Moritz HPF.PNG

  • Low Pass Filter (Pink Noise)

Moritz LPF.PNG

Build

White Noise Generator

  • Voltage Gain = 148
  • Switched from TL074 to TL084

ER-PROTO-01 NOISE WHITE Before.PNG

  • Output seems pretty quiet (~200 mV)
    • Issue is 2N3904 is much quieter than a BC548
  • Offset errors = about 500 mV
    • Gain = 148, 500mV = 3.5mV offset voltage
    • Add offset voltage trimmer
    • Circuit from here

OpAmp Offset Adj.PNG

  • Schematic with offset

ER-PROTO-01 NOISE WHITE.PNG

White Noise Scopecaps

  • White Noise Scope capture
  • 2 mS / div

White Noise Scope Cap-01.png

  • FFT, 25HKz range

FFT White Noise 25KHz.PNG

Blue Noise Generator

ER-PROTO-01 NOISE BLUE.PNG

Blue Noise Screencaps

  • FFT 1mS scope setting

FFT Blue J4 Noise 1mS.PNG

Pink Noise Generator

ER-PROTO-01 NOISE PINK.PNG

Pink Noise Scopecaps

Pink Noise Scope Cap.png

FFT Pink J4 Noise 1mS.PNG

Pink Noise LTSpice

ER-PROTO-01 NOISE Pink LTSpice.PNG

Jacks

ER-PROTO-01 NOISE J38.PNG

Connectors

J1 - White Output

  • +/- 7.5V swing

J3 - Pink Output

J4 - Blue Output

Eurorack Power

ER-PROTO-01 U1 PWR.PNG

Build

On Controls Card

ER-PROTO-01 NOISE P1080760-JacksRework-720px.jpg

  • Install J1, J3, J4
  • Wire J1-S to J3-S
  • Wire J3-S to J4-S

On Daughtercard

  • Transistor Noise Source wiring

ER-PROTO-01 NOISE P1080760-Trans Noise Source Rework-720px.jpg

  • Opamp wiring

ER-PROTO-01 NOISE P1080762 ANNOTATED-720PX.jpg

  • Wire J38-3 or J38-5 to nearby GND
  • Install U1 14 pin socket near "middle of card
    • Pin 4 goes towards +12V
  • Add 10 Ohm resistor U1-4 to +12V
  • Add jumper U1-11 to GND
  • Add jumper U1-8 to U1-9 (Blue loopback)
  • Add jumper U1-6 to U1-7 (White loopback)
  • Install R16 1K J1-8 to Open bus row (J1-T) - White noise out
  • Install R15 1K J3-6 to Open bus row (J3-T) - Blue noise out
  • Install R14 1K J4-4 to Open bus row (J4-T) - Pink noise out
  • Install 100K from U1-13 to U1-14
  • Install 22K from U1-13 to GND
  • Add wire U1-8 to R15 (new row)
  • Add wire U1-14 to R14 (new row)
  • Add wire U1-7 to R16 (new row)
  • Add wire U1-1 to U1-5 (NOISE_WB)
  • Rest per schematic

Debug

  • 60 Hz rail-to-rail noise on U1-1
  • 60 Hz noise disappears when scope is plugged in to output
    • Likely a "scope-ism" since it's not on the output

ER-PROTO-01 NOISE 60Hz U1-1.png

  • Switched to BC548 - much more noise
    • About 15x louder