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