SPL PASSEQ - Stereo Passive Mastering Equalizer (Red)The PASSEQ has revived the concept of the passive equalizer that was used in the 50's and 60's. The charming sound of this vintage technology combined with the modern 120V technology results in a very special equalizer. Only one filter All control functions are part of only one passive filter. There are three frequency ranges: Low Freq Mid Freq High Freq Each with a cut control on the left and a boost control on the right. In the middle is the output