381
Item nr.
Big sound from small amp
| Production | The Netherlands, 2014.
Price was 2 €. |
|---|---|
| Semi- conductors | 2x BC562C, 2x C3198, 2x D468C, 4 diodes (rect.), 4 signal diodes, 1 LED. |
| Cabinet | Plastic. Size 9x5x11cm. Weight 180gr (adapter 250gr). |
| Power | AC/DC, 9-16V. |
Amplified computer speakers contain a small power supply, stereo amp with 2 to 4W of max power, and small speakers in a plastic case. The power PCM (commonly found also in small radio sets like this Watssound) only does not contain the power transformer. Used sets (often with casing discolored) can be had at thrift stores at just 1 or 2 euro's. The idea of this project is to use the electronic parts, mount it into a smaller box and hide it under a desk to serve as music amplifier in the living room.
And yes, I still believe in big wooden speakers for better sound, so I connect the amp to my Philips 426 speakers of 1974.
| Obtained | 7/2014 from PC speakers. |
|---|---|
| Condition | 8. |
| Disposed | Scrapped 4/2020. |
| Sound sample | PLAY SOUND Mozart's Magical Flute sounds nice for this magical amp. |
I took out the electronic stuff out of the speaker and mounted it ito a plastic box (formerly holding ear tips). When placed in a drawer under my laptop, I found it became quite warm, not giving me a secure feeling. Punching holes in the lid didn't sufficiently reduce temperature. 
So I decided that the power transformer should be external, an adapter type that goes in the wall socket. These are known to be very safe and this will keep most of the developed heat outside my amp case. I spent some search time in my junk garden for an AC adapter, but then I realised that I could use a DC type as well. The PCB of the amp contains a bridge rectifier, but no single electron will be hurt from being rectified twice.
| Volts | Off | On |
|---|---|---|
| 3 | 1.7 | 1.7 |
| 4.5 | 1.7 | 1.8 |
| 6 | 1.7 | 1.9 |
| 7.5 | 1.7 | 2.1 |
| 9 | 1.8 | 2.4 |
| 12 | 2.6 | 3.4 |
For those who can appreciate the quality of an amplifier from a 1kHz block wave, here is a picture. The block wave of 1kHz comes from my Belco AF generator, and the output is visualised on my digital scope. There is some overshoot in the rise flanks of the block wave.
In 2019 I did an experiment and replaced the transformer by a switched mode supply. It turned out that the voltage switch on the transformer supply is very inaccurate, because in the 9V position, the voltage on the amplifier is actually 13V. I found that a real 9V is not sufficient for this amplifier to work well, and put in a 12V power supply. With this supply, the continuous consumption is 1.1W (when ON but without driving signal). So, as I expected, most of the continuous power goes into the transformer. The SMPS has a fuse and appears well-built, but because of all the stories about SMPSs catching fire, I banned a lot of them from my house again. My next amp, the AliAmp, is powered from 6V and even a 6V transformer takes no more than 1.2W vampire power.