Resistance value of resistor R1 is left up to the user depending on gain needs, R2 is unknown – for? experiment purpose. The op-amps are not critical, any standard ones could be used (eq: 741, LM324, etc).

Power supply used for this circuit depends the op-amp IC used. Use the IC datasheet to know the recommended voltage. Some op-amp IC needs symmetrical power supply to work, just find the op-amp which require general power supply (asymmetrical). A regulated power supply will be better for this circuit.

For better sound performance, use high quality component such MKM capacitor (non polar), tantalum capacitor (bipolar), metalfilm resistor, etc.

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Basic Tone Control Circuit Diagram

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This Hi-Fi tone control circuit can be operated with wide range supply voltage, 12V – 24V DC. Three potensiometers used for sound adjustment: volume level, bass and treble level.

Use good components (such as metalfilm resistors, MKM capacitors, tantalum capacitors, good cable quality) and stabilized/regulated power supply for better sound quality output, of course it will be need more cost.

The quality of components, cabling and power supply will affect the quality of the output.

This is a stereo audio tone control circuit which build based on IC? LM1036. This circuit will controll bass/treble level tone, volume and balance between right channel and left channel (input 1 and 2 ). You may use this circuit for stereo applications such as car radio, TV and audio systems, mp3 player, dvd player, ipod and more. An additional control input allows loudness compensation to be simply effected. The circuit should be works with supply voltage 9V to 15V DC.

Tone control features:

Wide supply voltage range, 9V to 16V
Large volume control range, 75 dB typical
Tone control, ?15 dB typical
Channel separation, 75 dB typical
Low distortion, 0.06% typical for an input level of 0.3 Vrms
High signal to noise, 80 dB typical for an input level of 0.3 Vrms

Schematic diagram:

Pre-Amp + Tone Control Components List:

Resistors:
R1, R2__________________ 220R
R3, R4__________________ 4K7
R5______________________ 2K2
R6______________________ 1K

Capacitors:
C1, 2, 7, 8, 17_________ 10 uF ecap
C3, 4___________________ 47 nF
C5, 6___________________ 15 nF
C9______________________ 220 nF poly
C10_____________________ 100 uF 25V
C11, 12, 13, 14, 16_____ 100 nF
C15_____________________ 1000 uF 35V
C18, 19_________________ 10 nF

Misc.:
IC1_____________________ TDA 1524A
IC2_____________________ LM 7812
P1______________________ 50k linear switch pot
P2, 3, 4________________ 50k linear pot
X1, 2, 3, 4_____________ RCA jack
D1______________________ Diode 1N4004
L1______________________ Red LED

Circuit Works:

All signal processing is done within the TDA1524A by voltage controlled amplifiers and voltage controlled filters. The IC provides a fixed voltage (~ 3.8V DC) at pin 17, and this is used by all the variable resistors to provide an adjustable DC voltage to the appropriate control pins.

Current sensing is used to provide a flat response when R5 is connected to pin 17, and a loudness contour when disconnected. 100 nF capacitors are used on each pot to decouple any AC signals from the control inputs. 10 uF capacitors are used to couple both input and output audio signals whilst blocking DC. R1 and R2, are to ensure stability with capacitive loads. R3 and R4 make sure there are no DC spikes at the output sockets if the load is switched. C3 and C4 control the loudness contour. C5 and C6 control the treble turn-over frequency. C18 and C19 have been added to roll off the gain above 70 kHz. Low volume settings coupled with treble boost was causing HF instability in some instances. This should no longer be a problem.

C15, 16, 17 provide power supply filtering. D1 provides protection in case of incorrect supply polarity. The LED is a power on indicator and may be omitted if not required, or preferably mounted on the enclosure. If you are not using a switch pot, you can connect an external switch across the P1 switch pins, or connect a wire link there and switch the power supply.

The power supply is critical to the noise? performance of the pre-amp. An on board regulator is provided to reduce mains hum. If you wish to use it with a car or other 12V battery, then you should omit the 7812 regulator, and place a wire link between the regulator input and output pin positions on the PC board. Do not short to earth! This will be necessary because the regulator must have an input voltage at least 2-3V greater than it”s output, for it to maintain regulation. However the regulator will not be necessary with a battery supply.

If using a plug pack, it”s output voltage should be 15 to 18V DC. Because most plug packs have poor regulation, one rated at 12V DC will often be around 15V when lightly loaded. The current drain of the pre-amp is less than 50 mA, so many 12 V unregulated supplies may be adequate if you have one. Replace D1 with a wire link if necessary, making sure you have the supply polarity correct!

If you are using a 15-20V supply for your power amplifier, you can use that as your pre-amp supply as well. Make sure you test the voltage first in all cases.

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Preamp and Tone Control with TDA1524A Manual

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TDA1524A Datasheet

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