Bass and Treble Cut

With the bass and treble controls both set to maximum cut (Fig. 0.0.5), the full bandwidth signal passes through R1 but with the slider of VR1 at the bottom end of its resistance track, C1/R2 now form a high pass filter having a corner frequency of around 7 to 7.5kHz so only frequencies appreciably higher than this are allowed to pass un-attenuated. The mid and higher frequencies are therefore fed to R3 and C4, which now form a low pass filter to progressively attenuate frequencies above about 70 Hz, the mid-band frequencies (about 600Hz) are reduced by approximately −20dB, and at 20kHz by as much as −43dB, as can be seen from the response curve in Fig 0.0.3.

Notice that although the circuit provides what is called bass boost and treble boost, with the passive version of the Baxandall circuit (with no amplification), all frequencies are in fact reduced.

The attenuation of the circuit at mid-band is typically around −20dB and with full ‘boost’ applied at either the low or high end of the bandwidth, attenuation at these frequencies would be around −1 to −3dB.