22 Watt Stereo Amplifier Circuit using TDA1554

The IC TDA1554 based Amplifier circuit discussed in this article can provide up to 22 watts per channel into a couple of four-ohm loudspeakers. The main attraction is that you can construct it for less than $15. This implies that you may make a power amplifier for your car's front speakers, another for the back speakers, and have 44 watts of absolute music power without spending a fortune.

About TDA1554 IC

Regardless of your level of skill with electronics, you will really enjoy building this circuit without any difficulty. Due to the project's small number of parts, you can simply put the amplifier together in one sitting. A single TDA1554 integrated amplifier IC, situated in the middle of the circuit, allows for such a low components count.

The TDA1554 IC was the best option for this project due to a variety of aspects. The price came first. Considering its low component count and outstanding sound quality and power, the chip looks surprisingly affordable.

Secondly, the TDA1554 was developed specifically for automotive applications in mind. It is powered by a +12 to +15 volt source with a 5 to 10 amp output. Consequently, employing the chip does away with the requirement for a separate dc supply. The TDA1554 works superbly with the car 12 V battery power itself.

Main Features of TDA1554 IC

The main characteristics of the TDA1554 can be summarized as given below:

• Turn-on-pop-free mute/delay circuit. Meaning, the speaker will never produce the annoying "thump" sound whenever the amplifier is switched ON or OFF
• Overheating or Thermal protection.
• ESD (electrostatic discharge) protection.
• Load-dump protection.
• In BTL (bridge-tied-load) applications, the input impedance is generally 30,000 ohms, while the gain is typically 26 dB.
• The power bandwidth ranges from around 20 Hz to 20 kHz.
• In the BTL setup, the output power is generally 17 watts at 0.5% THD and 22 watts with up to 10% THD.

Four separate amplifiers, a mute/standby switch, and some safety circuitry are all incorporated inside the TDA1554.

Using the BTL arrangement, amplifiers may be coupled to drive up to 22 watts into a 4 ohm load, or each amplifier can power up to 11 watts into a 2-ohm load.

This amplifier project uses the BTL concept for delivering up to 22 watts into a pair of 4 ohm speakers..

The mute/standby switching circuit uses a little delay and a slow turn-on to reduce loudspeaker switch-ON "pop" sound.

Each of the four amplifier sections has an input that may be either inverting or non-inverting. The device employs a BTL output design, as was previously explained, to squeeze 22 watts out of a nominally 12 volt DC system.

The fact that neither side of the load (in this example, the loudspeaker) is connected to ground causes this circuit to be occasionally referred to as a "bridge" or "bridged output."

In this arrangement, two 180° out of phase amplifiers are coupled with each other or bridged at the load.

Here, while one output turns high the other output turns low and vice versa. The audio input signals are supplied to the inverting input of one amp and the non-inverting input of the second amp in each stereo pair to achieve the 180° shift without the need of phase shilling circuitry.

In a single-ended load, when one terminal of the loudspeaker is connected to the amplifier output and the other terminal is attached to the ground, the result is often two times more power (into the loudspeaker) that each amplifier could produce.

How the Circuit Works

The following figure displays the 22-Watt Amplifier's schematic. Simply connecting to the vehicle's battery provides power for the circuit (+ 12 volts).

The ground of the vehicle is likewise connected with the amplifier's ground line.

Any unwanted signal hanging on the supply voltage is decoupled by capacitors C1 and C2, while ripple rejection is implemented by the capacitor C3 along with IC1.

Capacitors C4 and C5 connect the input audio signal to IC1.

These 10 uF capacitors are used to prevent the low audio frequencies from rolling off.
The mute switch circuit (contained in IC1) is fed by resistor R1 and capacitor C6, which creates the delay that prevents turn-on pop.

About 1.4 seconds delay is provided by their R/C time constant.

Although there are no passive components which may be absolutely crucial, significant changes in the values is not recommended.

In order to work normally the IC1 must have at least 8.5 volts at pin 14 (the mute switch). On the contrary, pin#14 must be maintained below 3.3 volts to keep the device in the mute state. At pin#14, the current requirements are in the range of 100 uA in the switched on condition and 40 uA in the standby mode.

A sufficient amount of delay is provided by the R1/C6 configuration (47 F and 39 K) to prevent turn-on pop noise, without delaying regular working of the circuit for an unreasonable length of time.

With this small delay, pin#14 does not turn on right away as it would do if a normal mechanical switch were used. Instead the potential at pin#14 slowly rises beyond the 8.5 volt limit as C6 charges.

R1 must not exceed 100 K, and the R1/C6 time constant must be on the scale of a second or two. However, the values of C6 and R1 are not crucial.

A time constant that is too lengthy will just result in a grating delay, while one that is too short won't always prevent the turn-on pop.

Current Consumption and Heat Dissipation

Before we move on to the actual construction of the amplifier, a few points regarding its current consumption and heat dissipation must be emphasized.

The total current expenditure for this design is around 5 amperes if it is operated to its maximum 22 watts per channel output with a sustained 1 kHz sine wave.

The amplifier will use no more than 2 amperes while you are playing music at a volume where the peaks are just starting to clip. This is because music naturally has a wide dynamic range. There are sometimes brief silences between beats and not all sounds are at their loudest.

Think about the contrast between, say, a bass drum and a harp being gently strummed. The majority of the power peaks are likewise transients, rather than continuous tones.

This means that if you utilize one of these amplifiers in an automobile application, consumption levels won't really be a concern. Nevertheless, if your car's engine is off, utilizing two or more amplifiers at high volume might deplete the battery soon.

When the unit is applied for home use each amplifier must have a minimum of three ampere supply or more to be able to withstand transient peaks.

Next comes the heat dissipation issue of the IC. The highest possible power dissipation of the TDA1554 IC is somewhere around 25 watts.

This is an indication of the heat which must be eliminated from the device from inside of the IC packaging.

There exists a thermal resistance between the chip and the IC container, between the IC package and the heatsink, and lastly between the heatsink and the atmosphere in the surrounding neighborhood.

As a result, a heatsink with a thermal resistance of 2.8° C/W or less is needed for this amplifier IC. As the chip heats and cools, poor heat sinking causes thermal shutdown or sporadic, unpredictable functioning.

This is exactly why, a proper heatsinking of the IC is very important. Make sure to use an optimally large finned heatsink on the IC for enabling it to function perfectly, regardless of the input transients and peaks.

How to Build

Our 22-Watt Amplifier model was constructed on a printed circuit board. You may either create your personal PCB using the copper layout depicted in the following image, or you could hire a qualified PCB designer, if you'd want to get the same results. In case you're employing a PCB, please check the following figure for the parts configuration layout as a reference.

Insert the C1 to start the assembly process. Keep one of the trimmed leads of the capacitors to use as jumper connections. You will need to insert the jumper wires next, and solder them into position.

By folding back one lead of R1 vertically, insert R1 on the PCB (standing up), and solder it. Now, insert the leftover capacitors subsequently, making sure to check the polarity prior to soldering.

Use wire cables of adequate lengths on the PCB, for the speaker connections, supply DC, and ground connections. An 18 gauge or stronger, insulated, stranded wire must be utilized for the power and ground lines.

For speaker leads, stranded 20 gauge wire works well. To eliminate misinterpretation, choose wires of different colors.

Shielded wires must be used to carry audio input signals to reduce humming, engine whining, and other unwanted sounds. Once they have been connected, join the wires to the J1 and J2 RCA phono jacks.

Mount IC1 on a heatsink first and then solder the IC to the PC board once all the other components have been assembled. Use a thermalloy extrusion heatsink or something comparable, as we recommended earlier.

Take two #6 screws and nuts to secure the heatsink after applying a small coating of heatsink compound to the backside of IC1. Screws need to be tight but not too hard, since this might harm the integrated circuit. Insert the IC1 pins into the PCB and solder them after removing any extra heatsink compound. Remember where pins 1 and 17 are located.

Look for and eliminate any solder bridges, cold-solder junctions, etc. physically.
Pins 2–5 and 13–15 on the IC are two areas where solder bridging should be closely monitored. The circuit can be housed inside an enclosure once it has completed a rigorous thorough inspection.

The amplifier can be housed inside a metal or plastic enclosure, but you should make sure that it is sufficiently ventilated so that the heatsink can function properly. Although plastic containers are sometimes less expensive, metal boxes provide superior protection and longevity in hostile conditions.

To function as a pilot light to show when the device is switched on, an LED in series with a 56K 2 watt resistor may be added to the circuit. Although there is no facility for an on-board fuse, it is strongly advised to install a 5- to 10-ampere fuse in the power line to the amplifier.

How to Connect and Check

As shown below, plug the TDA1554 amplifier circuit to your car stereo. First, connect the stereo's line-level audio source to the circuit board's inputs.

Car radio signals that are single-ended rather than bridged will serve as speaker-level signals.This can be found by looking at the radio's loudspeaker outputs at the rear.

The next step is to hookup one set of your car's loudspeakers to the amplifier. As we already explained, you should construct two amplifiers to accommodate two pairs of loudspeakers.

The amplifier works well with heavy-duty, 6 x 9-inch, three-way, four-ohm, oval loudspeakers.

The capacity of the current loudspeakers to handle power is yet another challenge; they must be certified for at least 20 watts RMS. Despite their wattage rating, tiny loudspeakers are only capable of producing a restricted volume of sound.

In most cases part, size matters, especially when it comes to the deep bass (the bass response drops down dramatically as loudspeaker size is reduced, especially at higher listening volumes).

This amplifier can easily power a pair of bookshelf loudspeaker boxes (10 inch woofer, 4 inch midrange, and dome tweeter, for example), however mounting such a speaker box in a vehicle is typically not practicable.

The TDA1554 amplifier circuit can power 8 Ohm speakers, but it can also drive 4 ohm speakers with higher power output. The majority of car loudspeakers have a four-ohm impedance, but double-check yours.

Finally, plug the Amplifier to your car's electrical system using the +12 volt power and ground connectors. Before securing the amplifier, test the amplifier system to make sure it is working correctly. Although it is totally up to you where the device is installed, typically people like to put amplifiers in the trunk.

A couple of these TDA1554 amplifier modules will produce superb sound and a substantial amount of power with powerful front and back speakers. Efficiency will be superior to inexpensive systems rated at "peak" power and on par with commercial devices in this power range.