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Sunday, 14 December 2014

Electronic 3 Band Equaliser Stripboard Veroboard Layout

There are lots of circuits on the net for 3 band EQs but I wanted something a bit more powerful than the usual 20+dB/20-dB things on offer so I went on eBay and bought some grey market MC3340P attenuators from china and made this thing.

I made mine for a send/return loop in a very simple valve amp I have but it's perfectly capable for hi fi audio.

it's worth noting that this works very well if you turn the knobs slowly because they aren't actually in the audio chain - they are part of the voltage control architecture of the chip

It's also worth noting that it will work on 9 volts if you want to make it into a guitar pedal.


  1. Hi, Paul. I wrote a longer post but it got eaten when I clocked "Publish"

    I've tried twice to build this but each time the result has come out the same. VR-1 seems to affect volume, from full to almost no sound. VR-2 has some very very slight effect on Treble. VR-3 doesn't have any perceptible affect at all. I've switched out chips, gone over it with as jeweler's loupe, and even started over to build it again. I can't find an issue or a deviation from your layout. I tried daisy-chaining lug one of all three Pots to ground and then I tried connecting each lug 1 individually to ground, doesn't seen to make a difference. This was all at 9v. I tried it at 15v and got the same results except for a pronounced hum.

  2. Any suggestions for how to get a little more oomph out of this thing? It does sound great and the interaction between controls is super versatile, but I was hoping for a little more bass content. I've adjusted input and rolloff caps to no avail. Currently this is feeding the 2w stereo layout you posted.