Meet Mr. EQ – a nice DIY equalizer –
While use of a graphic equalizer is often recommended for fine-tuning the tone of your instrument, no feasible DIY versions exist. However, a seven-band equalizer is not necessary to drastically shape the response of an instrument of effect. Adding peaks at certain frequencies can provide a pleasing result and is much easier for the DIY builder.
The Dan Armstrong Purple Peaker (and Yellow Humper, the sister version tuned for bass guitar) used two peaks for bass and treble boosts. The resulting effect is interesting, but not very flexible. We chose to apply the same concept, but with a modern approach that would provide added control to the user.
Mr. EQ – Link.