The Cheap and Dangerous AM-3668 TF Hi-Fi Stereo Amp

the substandard hifi stereo amplifier
Actually this is the name of this piece of Tech. First the price Ksh1200. I do not advice the buying of such type of very dangerous electronics. The purpose of this review is not to show how powerful this Amplifier is but also to highlight the dangers accociated with it. This type of amplifier is getting more and more popular despite it being sold uncovered with naked live wires exposd to touch. 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 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 mandrin?

the chinese or mandrin manual
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 -Very obvious

Okay now this amplifier comes as naked as it can be no plastic cover and with naked knobs. A shocker you can not power this amplifier after buying 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 does not even specify the amperage rating, mains frequency or the type of transformer to be used i.e. centre tap or single or does it in Chinese perhaps!

The only person who can buy this item is a person who has technical skills

The Electronics
Since the amplifier does not come with a transformer it has 3 pins for the transformer connection, a 4 pin bridge rectifier and two 4700µf 50V smoothening capacitors plus an LED for the power supply.

the back view of the hifi amplifier
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, now if they are a matched pair only the manufacturer can 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 midrange at the back left and two similar at the back right for the subwoofer speaker.

Testing the amplifier
To test the amplifier I used a 24V-0-24V 50 Hz 5 Amps Transformer.

For the speakers I used a 10 Inch Pioneer Subwoofer speaker and Two 3 Inch Pioneer speakers together with Two Semtoni tweeters for the midrange.

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. As for the quality of the music it’s not good. You can actually hear the distortion noise from the knobs as you turn them either to increase or decrease the volume. At no music at all and the volume turned to a maximum you can still here the noise despite the fact that it’s labeled Hi-Fi which by the way means High Fidelity, a function in modern quality music systems that reduces distortion and noise in amplifiers. Heat is another problem such that if attached a frying pan on the transformer I used I could fry some eggs. The fan actually does it's job of cooling the Mosfets pretty well.

This is a hazardous amplifier since it’s naked and with a mains transformer equally naked attached to it does not make things any better. It can deliver a fatal shock if the mains part are touched. This is not the type of music system you want near small children.

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Written by Gichane
Sunday, August 3, 2014