The input signal is applied to the non-inverting input of the lC which is a Siemens TAA861 operational amplifier.
Bass and treble boost and cut are con_trolled by the potentiometers RV1 and RV2 respectively. Control range is 20 dB of boost or cut at 50 Hz and 15 dB boost or 20 dB of cut at 12 kHz. The overall gain of the circuit at 1 kHz is 15dB and the input impedance is greater than 80 k ohm. Total harmonic distortion for 2.4 volts output is less than 0.5% and remains below 4% for up to 3.5 volts output. Correct law for the potentiometer is antilog. This may be obtained by using slide potentiometers which are mounted in reverse (end-for~end) to normal. Note that equalization is not incorporated in this preamplifier.
This simple single-transistor circuit will give approximately 15 dB boost or cut at 100 Hz and 15 kHz respectively. A low noise audio type transistor is used, and the output can be fed directly into any existing amplifier volume control to which the tone control is to be fitted. A The gain of the circuit is near unity when controls are set in the "flat" position.
Bass and treble boost and cut are con_trolled by the potentiometers RV1 and RV2 respectively. Control range is 20 dB of boost or cut at 50 Hz and 15 dB boost or 20 dB of cut at 12 kHz. The overall gain of the circuit at 1 kHz is 15dB and the input impedance is greater than 80 k ohm. Total harmonic distortion for 2.4 volts output is less than 0.5% and remains below 4% for up to 3.5 volts output. Correct law for the potentiometer is antilog. This may be obtained by using slide potentiometers which are mounted in reverse (end-for~end) to normal. Note that equalization is not incorporated in this preamplifier.
This simple single-transistor circuit will give approximately 15 dB boost or cut at 100 Hz and 15 kHz respectively. A low noise audio type transistor is used, and the output can be fed directly into any existing amplifier volume control to which the tone control is to be fitted. A The gain of the circuit is near unity when controls are set in the "flat" position.
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