Pre/De Emphasis

I am currently working on digital implementations of modulation pedals and I stumbled across the pre-emphasis and de-emphasis circuits used in most of analogue modulation boss pedals.

The list includes:

BF-2,

CE-2,

CE-3,

CH-1 (analogue),

CE-5 (analogue),

DC-2,

DD-2,

DD-3 (some versions),

DM-2,

DM-3,

DSD-3

GE-7,

HF-2,

RV-3

Although the functionality of pre/de-emphasis is useful for the pedal operation when the signal is on, I was surprised to see it is connected on the signal path when the pedal is bypassed. This is similar to the transistor-based input / output buffers found in most of boss pedals but the circuit has much more significant frequency shaping properties.

This is an example found on BF-2. First the pre-emphasis part:

Followed by the de-emphasis part:

Here is the frequency response (magnitude) of the pre/de-emphasis circuits:

Here is the combined magnitude and phase response plots between 10 Hz and 20 kHz:

Last updated: Sun 12 Nov 02:21:47 GMT 2017