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Hifi Pre Amp & Bass Treble with Active Volume
Click Here to download high gain stereo bass treble circuit diagram.
if you have used our Bluejay bass treble board then you will find this easy understand, for those who are new it is not that hard anyway.
This circuit has Four main sections namely - Regulated power supply, Input Buffer, Bass treble section and Gain section.
Regulated power supply section -
AC input supply at J2 is converted to DC by diode D1,D2,D3,D4 and filtered by C13,C14 voltage regulators U3 and U4 give fixed output of +12 & -12 volts respectively.
U5 is used to provide +5 volts to USB, Bluetooth or any other type of audio modules.
in simple words, regulated supply section converts AC to DC and provides +12v & -12 volts supply to other sections. +5 volt for other applications.
Pre amp Section -
One Op Amp from ic ( NE5532 ) U1 and U2 is used in the input section to amplify the week input signal.
Bass treble section -
This classic bass treble circuit designed by respected Peter J Baxandall was First published in Wireless World in 1952. You can see, nothing significant has changed since then. the following description is for one channel. other channel works the same just different part numbers so no use repeating.
Input signal is received through C14. At high frequencies the impedance of C12 is small and the bass control RV2 is effectively shorted out and R7, R8 give unity GAIN. At low frequencies RV2 is active with maximum boost / cut is set by end-stop resistors R7, R8.
At high frequencies again, C10 has a low impedance and treble control RV1 is active, with maximum boost / cut is set by end-stop resistors R3, R4. at low frequencies C10 has a high impedance, so RV1 has no effect.
U4 works as negative feedback amplifier. the amplified signal is sent to next stage.
in simple words RV1 is active at high frequencies and RV2 is active at low frequencies thus we get boost / cut in treble and bass respectively.
Active volume Section-
Another great circuit of respected Peter J Baxandall. this GAIN circuit amplifies the input signal to drive power amplifiers with minimum noise and distortion.
U5B U6B works as buffer and gain of U5A U6A is determined by R20 R22 & R21 R23 respectively. C20 & C21 ensures high frequency stability. this shunt feedback amplifier has gain of 17dB regulated by Dual Potentiometer (Volume ) RV1.
in simple words, signal received from bass treble section is amplified by ic U6 & U7. output of J3 be connected to any Aower Amplifier.