Chorus Circuit

Specifications:

- 2 Control Knobs: Rate and Depth
- Connectors: Input, Output, AC Adaptor
- Input Impedance: 470kOhm
- Signal/Noise Ratio: more than 90dB (IHF-A)
- Output Load Impedance: over 10kOhm
- Maximum Allowable input: 0dBm(100Hz), -10dBm(1kHz)
- Recommended AC Adaptor: ACA Series
- Current Draw: 9 mA (DC 9V)
- Weight: 400 grams (0.88 lbs.)
- Dimensions(mm): 70(W) x 55(H) x 125(D)

The circuit is designed around the MN3007 1024 stage BBD (IC3) and the MN3101 clock driver (IC4). The input and output circuits use a uPC4558C IC while the LFO is made with the help of a TL022LP op-amp IC.

Other active components:

D1, D2, D4, D5 and D8: 1S2473 or 1S1588 (switching diodes)
D3: 1S2473 (replaced with a wire jumper in newer models)
D6: RD5.1EB (5.1V Zener diode)
D7: RD11EB (11V Zener diode)
Q1-Q3: 2SC732TM-GR (NPN silicon transistors)
Q4-Q8: 2SC945-P (NPN silicon transistors)
Q9: 2SK30A-Y (Silicon N-channel junction field effect transistor)
LED diode: SLP-135B

Adjustment procedure:

Turn the Rate knob fully counterclockwise (min.) and the Depth knob fully clockwise (max.). Feed a 200Hz, +3dBm sine signal into the input. Connect an oscilloscope to the emitter of Q3 and turn VR3 until you'll get a centered operating point (a symmetrical sine wave, equally clipped at top and bottom).

https://www.hobby-hour.com/electronics/s/boss-ce2-chorus-schematic.php