8-Band Active EQ PUBLIC

8-Band Active EQ for Guitar or Bass.

8-Band active equalizer for guitar or bass. Controls include: Input Gain, 8 Q pots and 8 Level pots for frequency bands, Output Gain, Bass, Mid, Treble, and Volume. Uses one dual JFET-input op-amp IC for the Input and Output Stages, and two quad JFET-input op-amp ICs for frequency bands. Includes a Fender-style 3-band tone-stack. Bandpass Filter Center-Frequencies in Hertz (Hz) are; 55, 110, 220, 440, 880, 1760, 3520, and 7040. Total circuit gains per frequency with all pots at 50% and using a 1 V p-p 1 kHz input signal, are; 0dBV @ 33Hz, +8dBV @ 40Hz, +15dBV @ 82Hz, +16dBV @ 100Hz, +15dBV @ 250Hz, +16dBV @ 630Hz, +9dBV @ 1kHz, +16dBV @ 2.5kHz, +18dBV @ 4kHz, +14dBV @ 10kHz, +10dBV @ 16kHz, +5dBV @ 20kHz. Thus, circuit will work for 6/7/8-string guitar or 4/5/6-string bass, with general emphasis from 60Hz to 10kHz. Moderately hIgh gain overall. Maximum total circuit gain = +36dBV @ 4kHz with all controls at 100%. Circuit is intended for rack-mount applications only. Power-supply not shown. Requires a regulated dual-polarity +-12V DC power-supply providing >= 50 mA of available current. Though verified, treat as experimental. Breadboard test before committing to a soldered build. House completed project in a grounded metal enclosure to prevent EMF interference.