TDA2822 - Rather basic sound and limited power.
Key specs: 1.8-15V supply, 2x1.2W in 8 Ohm, 0.3% THD, 6mA quiescent current.
DC offset measured at outputs: DC decoupled through electrolytic output capacitors.
With this short test of the TDA2822, some readers may ask themselves if we are serious about sound quality? Our interest is sound replication at moderate cost in general, also circuits that do not qualify as high fidelity. Actually, the TDA2822 may comply with the old HiFi norm (DIN45500) but it is a circuit that is rather limited in many ways.
A small and inexpensive board popped up during ordering of other items and why not? A couple of click's and it was added to the purchases. TDA2822 can handle up to 15V supply voltage and can be bridge-coupled such that the output power is increased about four times.
The TDA2822 can be seen as a dual version of LM386. The TDA2822 has a DIP-8 housing similar to the LM386. Both are intended for low power operation from a low voltage supply, often a battery. TDA2822 is supplied by more manufacturers. An important supplier is STMicroelectronics from whom the specifications above are found. A further important information is found under Absolute Maximum Ratings where the output current must not exceed 1A. This information is important for the use of bridge-coupling and supply voltage.
With an 8 Ohm load, which is normally the highest impedance of external loudspeakers, a maximum current of 1A corresponds to a voltage of 8V. Thus, if a bridge-coupling is used, a supply voltage of maximum 9V can be used. Therefore, the full supply voltage (12v-15V) cannot be used. Worse, with a 4 Ohm load only 5V can be used as supply. It follows that bridge-coupling merely makes sense for load impedances above 8 Ohm.
For normal stereo operation, with DC decoupling capacitors inserted in series with the loudspeakers, the voltage across the loudspeakers is maximum half the supply voltage. With 8V (for 8 Ohm impedances) this means that the full supply voltage of 15V can be used without exceeding the absolute maximum current. Hence, with normal 4 or 8 Ohm loudspeakers the ordinary stereo coupling should be used.
The TDA2822 board we got our hands on was equipped with a chip from STMicroelectronics. Always watch out for differences in the specifications if not the same manufacturer. The board was left in its original configuration but the assembly was cleaned up a bit.
The board could only be tested at normal sound levels due to the limited power. A 12V supply was used. The sound could be described as absolutely reasonable seen from the views of an ordinary person - not for an audiophile. The TDA2822 board appears to miss the clarity of the better boards tested here. The deep bass is appropriately damped by design such that the TDA2822 is left more margins in operation. The chip performs quite well with music dominated by vocals and acoustic instruments. For music with a more permanent sound floor and eventually dominant bass, the TDA2822 may soon be exhausted. To compare with something known, the sound of the TDA2822 can be compared to the sound of an ordinary FM tuner.
The TDA2822 is suited for driving smaller loudspeakers. It is particularly suited as driver for headphones when no particular performance is demanded. Implementation requires a minimum of peripheral components. The TDA2822 has got the particular quality to be able to function with a supply voltage of only 1.8V. It is not evident to make circuits function with so little tension.
In the data-sheet it is mentioned that the TDA2822 is intended for use in portable cassette players. This gives a hint to the age of the design but also why low voltage operation is important.
Comparative tests will not be performed with the TDA2822.
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