a collection of power supplies

Transformer vs. PSU for your Car Audio amplifier


I have the same as shown in the Pictur and I am enjoying the music. The music is so clear especially in  a good surrounding. The problem is how to connect it, I only use 2 channels but the picture above has really helped me a lot. I am using a transformer for powering it but I need some more assistance from you guys on how to give it the best power input. Thanks.

This is a query from Sirya on the post about the JEC 3245 Car Audio amplifier that I did some while ago. You can see the amplifier he refers to as “shown in the picture” in that post. And here is the reply that I promised Sirya in the comments section.

Its not advisable to use a transformer on  your car audio amplifier because of the unstable voltage it produces. Car audio equipment is designed to work on 12Volts. Your transformer I presume is one of that a local fundi or technician built for you with some diodes for rectification and a smoothening capacitor. The transformer may be producing 12Volts but after rectification and smoothening the voltage is usually higher. Some home made transformer power supplies for this purpose can produce as much as 16Volts. The other reason is that transformers if loaded beyond their capacity will have a voltage drop. For example in order to play a bass note, an amplifier requires more power. In the demand for more power, the current in the cable usually rises and the voltage at the source drops. In fact if you place a Digital multimeter on the two terminals while music is playing, it will be noted. These circumstances are perfect for an electrical fire because in most electronics, if the power demanded is more than required, the fuse usually blows. Does your power supply have a fuse?

The other reason why transformers are not recommended is because of the heat produced. Transformers produce heat because of two reasons. First because it copper losses because of coil resistance and secondly because of eddy currents which are caused by the electromagnetic effect. This weakness of transformers make manufactures use fans ton cool the inside of a product by drawing out the hot air. The photo below is of an LG HiFi power supply.


Note  that it is a switch mode power supply, SMPS. Switch mode power supplies produce very little heat as compared to Transformers. They are also very light and produce stable voltages because of their feedback design. To add to the advantages, they have short circuit protection. The fan you can see in the picture actually serves the audio amplifier circuit, I am sure you know very well your JEC Amplifier produces considerable amount of heat while playing music.

Its not advisable to use an adapter as it will not produce the required current while playing loud music, The best thing to use is a computer power supply.  It is a switch mode power supply and it produces a high current at a constant 12Volts to your amplifier.

You said in your comments that you are only using two channel which is only utilizing half the capability of the Amplifier. Make sure you feed all the ports with a signal using an amplifier wiring kit. Connect the mid range speakers to the front CH1 and CH2 and the subwoofer(s) to the rear CH3 and CH4. Bridge the subwoofer for louder bass and enjoy you music.


    Thanks Techsawa..I like the way you make deep physics look like child’s play. I always know that bass needs more power which explains why small transistor radios in rural areas sound like tutors(And why do they use the term transistors). I now know thanks to this article. So much knowledge in here. Thanks.

    • They use transistors because they are the amplifying components in the radio. Nowadays MOSFETs are used because they switch much faster than transistors and produce less heat and are easier to fabricate. Most car audio amps utilize MOSFETs in both the power supply and the amplifying portion.