Wednesday, December 07, 2016

Audio Booster circuit

The following circuit is Audio Booster similiar as Tone booster  ( Bass and Treeble ) has a maximum gain of around 22 dB (voltage gain). The frequency response of the amplifier is determined mostly by the value of just a couple of components, primarily C1 and R1. See the following Audio Booster circuit below : 

Audio Booster circuit tone booster

Component List :
R1 : 47K
R2 : 470K
R3 : 10K
R4 : 560R
R5 : 270R
P1 : 100K
C1 : 0.1 uF
C2 : 0.47uF
C3 : 220uF
Q1 : BC549

The values of the circuit diagram present a response of ±3.0 dB from about 120 Hz to higher than 20,000 Hz.In fact, the frequency response is ruler flat starting from about 170 Hz to more than 20,000 Hz; it's the low end that deviates from a flat frequency response.

The low end's roll-off is primarily a function of capacitor C1(since RI's resistive value is fixed). If C1's value is replaced to 0.1 pF, the low end's comer frequency-the frequency at which the low-end roll-off starts-is reduced to about 70 Hz.

In the event you want an even deeper low-end roll-off, change C1 to a 1.0 pF capacitor; if it is an electrolytic type, make particular that it is installed into the circuit with the proper polarity, using the positive terminal connected to Q1's base terminal.


  1. I made this circuit on test board first, and it doesn't work. Any ideas? I have plugged 9v battery.

    Photo below:

  2. Is R5 supposed to be connected to an LED ? As drawn it doesn’t do anything except waste power.


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