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Treble Control. A passive circuit used to attenuate frequencies in the lower audio ranges.
Minimum Component Treble Control
The output is taken from the center tap of a potentiometer which is connected between two frequency dependent capacitors, being used as filters. The variable resistor acts as a gain control, changing the position of the potentiometer will cause the output to increase or decrease regardless of frequency. The value or setting of the potentiometer does not vary based on frequency. Adding the resistor, just adds a fixed value to the output. That is, fixed depending on the setting of the resistor, but fixed in frequency.
 Treble Control | The circuit is configured as a frequency dependent voltage divider. Ignoring the resistor, the output voltage is C2/[C2+C1]. Capacitor C2 should be smaller than capacitor C1, a factor of ten would be a nominal starting place. If C2 is made smaller than it will have a larger capacitive reactance at higher frequency. A larger reactance means more gain at higher frequencies, because the output is taken across C2 and some portion of the resistor. |
Loaded Component Treble Control
A more realistic circuit uses a load being driven by the volume control. In the particular case R2 needs to be much greater than the load [R2 > 10 x RL]. Otherwise the load would swamp out resistance of the potentiometer [R1 // RL].
 Loaded Treble Control | This circuit modification is just used to show that the value of the potentiometer does matter. So a 1K potentiometer value might not work, depending on the value of the load resistor, while a 10k or 100k might provide better results. In any case each of these examples are using the minimum amount of parts to show an example not provide a finished design. |
F1 = 1/ [2 x 3.14 x RL x C2]
F2 = 1/ [2 x 3.14 x RL x C1]
Common Treble Control
Treble Control
R3/R1 = C1/C2
R2 > R1 > R3
C1 = 1/ (2 x 3.14 x F1 x R1)
C2 = 1/ (2 x 3.14 x F1 x R3)
F1 = 1/ (2 x 3.14 x R3 x C2) = 1/ (2 x 3.14 x R1 x C1)
F2 = 1/ (2 x 3.14 x R3 x C1)
Note R2 needs to be larger than both R1 and R3 for the equations to work.
Related Audio Topics;
Audio Base Control.
Audio Tone Control.
... 2-Band Active Tone Control
... 3-Band Active Tone Control
Midrange Adjustment Circuit
Loudness Adjustment Circuit
Audio Crossover Network
