Power amplifier electronic circuits-tube audio rf amplifiers

Electronic Amplifier Circuits-Power amplifier, audio amplifier designs and circuits

March 18th, 2008

Stereo preamplifier circuit with Tone control

About the circuit.

Here is the circuit of a stereo preamplifier circuit with built in tone control facility.A very useful circuit using versatile tone control IC TDA 1524 from Phillips.

The circuit is designed as per the data sheet as an effective stereo-tone & volume control for car stereos , TV sets or  any sort of stereo amplifier circuit you want.The circuit  includes provisions like bass control, treble control , volume control with inbuilt contour or linear mode option (can be switched in betwwen) and balance. All these functions provided can be controlled by DC  voltages or by  linear potentiometers.

Circuit Diagram & Parts List .


Tips .

  1. R1 ,R2 ,R3 andR4  can be used for controlling volume,balance ,treble and bass respectively.
  2. If SPDT  switch S1 is in position 1 ,the circuit works in contour mode and  in position 2 the circuit works in linear mode.
  3. The circuit can be powered from 7.5  to 12 V DC supply.  Do not give more than12V.

TDA1524 quick reference data .


March 18th, 2008

2×22 W stereo amplifier

About the Circuit

This is the circuit diagram of a powerful and good quality stereo amplifier using IC TDA 1554.Even though the circuit has only very few external components.The circuit delivers a 2×22 W out put on 4 Ohm speakers.The most great factor is that it operates from a 12 V power supply, which makes it ideal for car stereos.

My experience with the circuit

The circuit was designed as per the data sheet and so there was no room for error, and I found it working great.But it didn’t last long because I raised the power supply to 40V and the IC blowed up. Lesson : Don’t give more than 18V power supply to TDA1554!

Circuit Diagram & Parts



There is a lot of heat generated during the operation of IC , so it must be connected to a suitable heat sink. A small cabinet fan can also be used in addition for better cooling(not necessary)..The circuit draws about 6A current at 12 V at full out put power.So the power supply must be some thing that shoul be able to deliver more than 6A at 12 V.The maximum rated supply voltage for TDA 1554 is 18V.Do not give more than that.I recommend 12 V.

March 17th, 2008

Audio Wattmeter for amplifiers

 About the circuit

This particular circuit is very useful ,especially in cases where the measurement of the amplifier output is to be done. The maximum power of the amplifier, which is to be measured must be only half the resistance R2  that acts as the  load for the amplifier.A very good result can be obtained if the meter scale is calibrated,and with a little more hard work.

Circuit Diagram & Parts List 



  1.  If you cannot get a 1A no problem , make one with four 1N 4007  Diodes.
  2. The resistance R2 must be rated double the power of amplifier you are going to      measure.
  3. To calibrate  the watt meter, Connect the output of amplifier to to port 1.Also connect a AC voltmeter to port1.
  4. Set R1 fully off.That means full counter clockwise rotation if wired correctly.
  5. Adjust the output of amplifier to read 20V rms on the voltmeter.This is the equivalent of 50Watts on 8 Ohms load.
  6. Set R1 for a full scale deflection on meter M1. Now fix the wiper of preset R1 using some adhesive.
  7. Now decrease the voltage across the port 1 by decreasing the output power of amplifier under test  as per the the table shown below and mark the readings on the meter scale.The watt meter is now ready to measure.

 Table for Calibration