By: Dhrubajyoti Biswas
This article will detail building a stereo amplifier along with an output for a headphone jack. It is built by using the IC TDA2050V integrated circuit. According to the data sheet that comes along with the IC, TDA2050V is ideal for Class-AB based audio hi-fi amplifier.
The required operating supply voltage for TDA2050V should be in the range of +/-4.5V to +/-25V.
Using 25 watts of power you can achieve at least 65% efficiency. However, it is important to note that to maintain stability on the system the circuit gain should be managed with a gain of around 24dB.
We built the amplifier with an intent to use it with RB-51 bookshelf speakers. They are 8 ohms possessing a sensitivity of 92dB @ 2.83V / 1m.
Since this amplifier utilizes less power, therefore using TDA2050V is quite a right choice.
Moreover, the amplifier will also work with other audio devices, such as, tuner, mp3 player etc. It may be interesting to note that, the smaller TDA2050V chip produces a better quality sound than the bigger version.
Constructing the Amplifier
The above diagram is of an application that uses split-supply. The diagram is taken from the datasheet for ease of understanding. Also it is advisable to read the datasheet that comes along with TDA2050V chip. This will help to understand setting up the stereo in different ways.
The datasheet specified for the IC also details a recommended PCB design, which we have used as a reference for this experiment. The figure above, taken from the datasheet shows the basic PCB layout:
The amplifier that we have built in this experiment, its schematic design is presented below
Schematic of hi-fi amplifier using TDA2050
To build the circuit, here we have followed the PCB design as shown in the above figure. Also, the circuit could be simply assembled on a perfboard.
In order to block DC current flow, we used a capacitor of 1uF MKT type. However, there is no such restriction and you are free to go for any other relevant capacitor as per your choice.
Constructing a circuit is not at complex. However, there are certain vital factors that should be kept in mind during design, as stated below:
- Grounding or earthing is very important to maintain low noise and an hum-free response from the system. This is why star grounding process is probably the best suited in this case. The system employs two ground points, use one for signal and the other for power, further connecting both of them via singular connection.
- For each channel use individual power supply.
- Keep signal wiring short and ensure the wires are twisted tightly. Maintain a distance with the AC power sources. Also it would be better if you can keep the wiring close to the chassis.
In this amplifier design the power supply adheres to the standard power supply regulations and employs snubbers for better safety.
Besides, we used torroidal transformer of 120VA and 18 Volt dual secondaries. Also we used 35A rectifier bridges, however, you can also use 15A – 25A bridge.
As per the design of specs, it uses MUR860 ultra-fast recovery diodes. You can also try other discreet diodes that are ultra-fast, but as per this experiment we figured out that it can be ignored and normal rectifier diodes can be used.
You can find 10,000uF capacitor for each power supply. The hum suppressed by the supply is quite inaudible albeit we could hear some on a microphone, when it has max volume and has no signal connection.
TDA2050 Power Supply Design
For the enclosure, here we used Hammond’s chassis [Model ID: 1441-24]– 12” x 8” x 3”, steel built and satin black in color.
The circuit board and transformer was carefully placed above just on the top of the enclosure. The volume control, headphone input and power button was placed at the front for ease of use.
We used gold-plated RCA standard jackets for the input. For output we used standard output plugs of three-way binding posts, which accepts bare wire, 4mm banana plugs or spade connector. However, please note that the binding posts of the speaker and the input jackets have their insulation from the chassis made by nylon spacers.
As a standard procedure we have placed the heat-sink on the rear of the chassis, which is measured 50mm x 88mm with 35mm fins @ 2.9 C/W. Also we need to make a hole on the chassis so as to mount TDA2050 directly. As a note, please ensure TDA2050 is kept separate from the chassis because of the potential issue on TO-220 package. If this is not taken care of, then there is high chance of the chip to get destroyed once the system receives power.
In regard to isolation, you can use mica or silicon pads. Also please keep in mind to add a spacer for mountain crew to save the chip. Upon setting up the system, do finally check all the components and their placements. For instance, ensure a check to avoid continuity between heat-sink / ground / chassis and the chip.
As a conclusion, do maintain good thermal contact. Here we used thermal grease before mounting the system.