The Boss GE-7B pedal is a 7 band (62Hz - 4kHz) equalizer with a boost/cut of 15dB per band, designed specifically for bass guitars. The schematic is similar to the GE-7.
Fig. 1: Boss GE-7B Bass Equalizer guitar pedal schematic diagram
Fig. 2: GE-7B PCB - component side
Specifications:
Residual Noise Level: less than -100dBm (IHF-A Weighted, Typ.)
Equalizer Control: 7 bands, +/- 15dB
7 band EQ: 62Hz, 125Hz, 250Hz, 500Hz, 1kHz, 2kHz and 4kHz
Level Control: +/- 15 dB
Input Impedance: 470kΩ
Output Load Impedance: more than 10kΩ
Connectors: Input Jack, Output Jack, AC Adaptor Jack
Power Supply: DC 9V dry battery, AC Adaptor
Current Draw: 12mA (DC 9V)
AC Adaptor: ACA-Series
Width: 70 mm
Depth: 125 mm
Height: 55 mm
Weight: 450g
ICs, transistors and diodes used in the Boss GE-7B Bass Equalizer:
IC1-IC4: M5218P (dual operational amplifiers)
IC5: HA1457W or HA12017 (low noise preamplifier)
Q1: 2SC2240GR (NPN silicon transistor)
Q2, Q3: 2SC945-P or 2SC1685 (NPN silicon transistors)