To amplify the output signal of the mp3-player for a headphone, which will be attached to the wheelchair, I've screwed this Behringer headphone amp under the seat.
Even if the sound quality was very good, the maximum output volume of the amp was too low.

Then, I replaced it by those two 12W mono NF-amps from Conrad. This decision turned out to be stupid. 12W are far to much, so the amps destroyed the headphones. And furthermore, the sound quality was ultra bad.

Next, I tried the TDA7052, which is shown below. This is a 1W NF-amp, mainly intended for the use as headphone amp. I don't know exactly why, but I did not get the thing running. In a mixture of disappointment, anger and curiosity, I wanted to find out, what is inside that IC.

I've hit the thing with a hammer, but there happened nothing else than bending the pins away.

I've hit the thing again, this time a bit harder, and then I could see, what was inside it.

This is what was hidden inside the plastic housing of the so-called "NF-amp". For me, it just looks like a little piece of metal. No wonder, that it did not amplify anything at all.

My fourth try, was to use those two mono amplifier modules. They seem to be quite old, because they were produced in the GDR. However, the sound quality of them is not very good - but good enough for the use at the wheelchair. And their loudness is also alright. I am not 100% happy with them, so this will be a piece, which I will probably change later. But for now, I will use them and I started to build them a proper housing.

I wanted to build it out of metal, so it shields the amplifier from the motor's electromagnetic noises. When I am building such a case, I usually start as I would build it out of paper. I draw the shape of it onto a sheet of aluminum and cut it with a metal scissors.

Then, I bend the metal. I am using bolts to connect it at the corners.

This is the final housing.

This is the opened housing with the amps inside. Unfortunately, this was the last picture on the film, so I can't show you the final version, which is fixed under the seat and which has some additional volume potis. There are pictures of it on the next film, I guess. But this still has to be developed. And don't hit me, if I am too lazy to upload those pictures, then.

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