Asser Rodriguez(amini-p7)

Miscellaneous Projects

When I decided to build this project, I had a few doubts about which box to use. The ones on the market were not the size I needed, so in the end I decided to design it myself. The material I chose was some simple aluminum sections and ventilated stainless steel sheet. They are easy to mechanize and the result is a very rigid structure. The dimensions are 40x30x15.5 cm. The use PCB are of Kristijan Kljucaric, a good design for a deserved circuit. Like protection measurement, I use the Kit Welleman 4700, by that to avoid DC in the loudspeakers In series with the power CA, I have connected a heat switch with off to 70º. One fuse de 10A in each branch DC. All the capacitors are of Polypropylene. The resistors are of metallic film. The power supply is classic: 1 toroidal tranformer 15+15V 330 VA. 2 rectifyng bridges 35 A 600V. 4 electrolitic capacitors 22.000 uf each one, 25 V. 2 capacitors MKP 2,2 uf 160V. At the moment I do nod have including the shock coils of 2,2 mH The output stage MOSFET are IRFP 240. Out of the 20 units I was sent, I could match the 4 required. Initially, they are connected with a clamp. When I finish the tests, I will weld them to the circuit. The heat sinks are 2 aluminum bars with wings, 40 cm long, 0,5C/W, according to the manufacturer. The temperature they reach is 63ºC (145ºF), which is normal in class A. The VU meter instruments, although they are not necessary, serve as decoration (Atrezzo), and make the box a little bit more pleasing to the eye. LISTENING The noise is not noticeable in the normal listening position, although if you are about 15 cm away from the loudspeaker you can hear a slight humming, which is not at all annoying. I suppose that the noise level will improve substantially when the shock coils are included. It is very difficult to express with words the advantages of an audio amplifier, as it forms part of each person's different feelings and emotions. To give an example, I will say that this concept seems to be easier for "Wine Tasters", since they use an infinite number of terms to differentiate the quality of one wine and another: Velvety taste, a certain touch of wild fruit, toasted wood aroma, etc. I cannot go that far, and I will say that one of the main things that you can ask of a good amplifier is for it to sound natural and balanced. The Mini Amplifier exceeds those expectations. The approximately 10 W power is, for me, more than enough to listen to Folk, Jazz and Classical music in a 15 m room with some loudspeakers B&W of 90 dB/1m. ACKNOWLEDGEMENTS I would like to thank the members of Pass DIY. Even though I have not taken part in this one Forum, the explanations and recommendations given in it have been very useful to me. My thanks also to my nieces, Carina and Susana, for getting me the MOSFET transistors . A special mention, for his good work, is for the creator and designer of the Amplifier, Mr. Nelson Pass. Asser Rodriguez Spain

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