In a linked stereo EQ, the potentiometers need a lot of layers. The pots for setting the mixers (gain) have two layers each, while the pots for setting the frequencies even have a total of four layers each!
The problem occurs that every single layer has its own component tolerance, and while layer A could be at the absolute minimum of the allowed tolerance, layer B could be at the absolute maximum. As a result, the filter stages of the left and right channels would not behave the same.
To solve this, every single potentiometer in the xfilter is measured and selected with an Audio Precision rig and computer routines written exactly for this task. As a result, only 65% of the dual layer pots and only 50% of the quad pots we buy go into production – the rest is put aside.
And this is no marketing BS, but the very basis for producing an equalizer that is not only linked, but accurate as well. It's a true custom shop option we are proud to offer with every xfilter free of any up-charges.