The Cheap HiFi Stereo Amplifier

This amplifier cost me Ksh1200 and I do not advice the buying of such type of very dangerous gadget. The purpose of this review is not to show how powerful this Amplifier is. The purpose is to highlight the dangers associated with it. This type of amplifier is getting more and more popular in Kenya. From the shops it is sold uncovered with naked exposed live wires. Just check this link out and maybe you can get yourself a good quality Car Audio amplifier at a lower price at Anisuma. You should also check out Precautions when powering a Car Audio amplifier using a computer power supply.

The Manual

The following words in bold are all the words on the packaging of this device.

HI-FI STEREO AMP– Presumably the amplifiers name

OK-100W-The amplifiers power output perhaps

DX-2.1-3-also presumably the speaker ports .The 2 may represent midrange output, the 1 may represent subwoofer output and 3 its obvious the total.

AM-3668 TF-No clue may be the model number
AM-7294 TF-?

Now to the manual, it’s written in Chinese or is it? The only legible part to an English reading person is. Is it Chinese or Mandarin?

2.1CH -Like above this presumably is the speaker orientation

3X80W –Now the power output has changed from 100W on the packaging to 80W?

8?– obviously this is the speaker impedance

AC 18V – 26V -The operating voltage! Why the large variation

20Hz – 30 KHz- Again obviously the amplifiers frequency range from the lowest subwoofer frequencies of 20Hz to Tweeter frequencies of 30KHz.

-R +R –L +L – obviously those are the speaker output terminals

Okay now this amplifier came as naked. That is without a cover. The knobs too were naked. I had to buy the plastic knobs separately. So this meant that I could not power it.

That’s right you have to buy a transformer to power it and not any transformer but the one specified in the Chinese manual that an English reading person cannot read.

The manual did not even specify the amperage rating. Even the mains frequency or the type of transformer was not specified. Was it meant to be used with a centre tap or single coil transformer?

The Electronics

The only person who could buy this item is a person who has technical skills. Since the amplifier did not come with a transformer it had 3 pins for the transformer connection. That is a 4 pin bridge rectifier and two 4700µf 50V smoothing capacitors plus an LED for the power supply.

For the amplifier section it has 6 Mosfets attached to a golden coloured heat sink which in turn has a fan attached to it at the back. Each channel is driven by a pair of Mosfets. I couldn’t tell if they were a matched pair. That is because only the manufacturer could answer that.

Control is provided by 4 naked rotary potentiometers at the front. The inputs are two RCA ports on the right and outputs are 4 clamp on connectors for the mid-range at the back left and two similar at the back right for the sub-woofer speaker.

Testing

To test the amplifier I used a 24V-0-24V 50 Hz 5 Amps Transformer. For the speakers I used a 10 Inch Pioneer Sub-woofer, two 3 Inch Pioneer speakers and two Semtoni tweeters.

After connecting everything it was time for the music, a little hip-hop from Ryan Lewis and Macklemore, drake and Paul Wall and some Reggae from Shabba ranks and Burna Boy and some mixes all day long.

The Verdict
Its loud I have to admit, just picture the loudest matatu you have ever been in this is how loud it is. The sound quality is not great. Distortion noise can be heard just by turning the knobs. With no music at all and the volume turned to a maximum you can still here the noise . This is despite the fact that it’s labeled Hi-Fi which by the way means High Fidelity. HiFi is a function in modern quality music systems that reduces distortion and noise in amplifiers. Heat is another problem. But the fan actually does it’s job of cooling the Mosfets pretty well.

This is a hazardous amplifier. It has naked wiring and an equally naked mains transformer attached to it. The user can receive a fatal shock if the mains part are touched. This is not the type of music system you want near small children.