xfilter

If you look under the hood of an audio equalizer, it is very likely that you will find a lesser or greater number of film capacitors. These caps use an insulating plastic film as the dielectric, which is drawn in a special process to an extremely thin thickness.

There are several technical reasons why film caps are a good choice for audio filter circuits, and generations of audio engineers will confirm that they sound great, too.

A typical representative of this component is the MKS film type, which is a great sounding cap to be found in many EQ designs. However, many MKS types come with a typical tolerance of 10%, which can have a negative influence on the channel accuracy of a stereo linked EQ.

For this reason, the xfilter uses a special FKS type film capacitor which sounds just like a good cap should, coming with a maximum tolerance of 5% only. One more step towards a more accurate stereo image.

The PCBs of the xfilter have a total of four layers: Two of them are used for the audio circuitry, one is for power supplying traces, and the last one is a dedicated ground shield layer. But what’s the idea behind this?

The filter networks of the individual bands of the EQ become higher in resistance the lower their specific frequency is set. This makes them more vulnerable towards hum which is caused by electric fields.

As the additional ground layer is placed extremely close beneath the traces which carry audio, it is very efficient as a shield against unwanted noise interferences.

We love the sound of class-A circuitry! And here is why: In a class-A amplifier, the transistors are conductive all of the time, so there is no crossover distortion at all. This is the perfect technological basis for an open sound with massive punch and no degradation of your original source.

The discrete approach makes it possible to design every single stage in signal processing exactly to what you want it to do – physics becomes the only limit. The xfilter uses our custom discrete input and output stages derived from the alpha compressor. The mixing stages are also discrete designs running in class-A mode.

The actual filter stages (band pass etc.) use integrated op-amps instead, and also in this regard we did not go for an off-the-shelf solution. Instead of cheap industrial standard op-amps, the xfilter uses high grade Burr-Brown OPA series amps which have been designed especially for the critical discerns of pristine audio circuitry.

And there it is – the expensive sound of boutique high end EQs in an affordable package.