Here is a pretty basic Bass and Treble tone control circuit. This was originally designed using the ua741 op-amp, now updated to use the NE5532.
The frequency response, with the tone controls centered or on bypass, is about -1db at 20hz and flat to 20khz. The gain is unity, with the controls centered or on bypass. The controls can affect the usual + or - 12db curves centering on 800hz.
Please note: This is not a production circuit. The original worked just fine but the updates for the new op-amp may require a bit of tinkering to get it just right.
Single rail supply line for tone control was designed in the days before op-amps were made & pnp transisters were not readily available to match npn, so they designed things to Quasi Complementary designs. NE5532/34 are design for split rail design, how much extra noise does the single rail design add when compared to a split rail (modern) design.
