Miscellaneous Projects

The following is a quote from a question I posted on the diyAudio.com forum back in Feb-2002. I have completed building my BOSOZ and I'm ready for my next project. I would like to build one of the A series power amplifier. I choose to build the A series amplifier because I have a ZEN amplifier already and I want more power than a SOZ. My goal is to do the least amount of work (read: utilizing available pcb from the web) but still be able to achieve maximum enjoyment - listening - and be able to get parts easily in the least amount of time. Which A Power Amplifier should I built accordingly to this goal? I have read about A3 and A4 in the PassDiy web site with quite detail description of construction and even a board layout. Recommendation please from those of you who have gone through this process before or who has built several different models of A Amplifier already. The following is a quote of a response from Nelson Pass. Build A2's. Some general construction notes and comments. On the right, you'll see some pictures of the A2's that I have build. The amplifier measures 13.5" X 13.5" X 10"H and it weighs about 50 pounds each. The aluminum sheet metals are 3/16" thick. The handles at the back of the amplifier are very handy for moving the monoblocks from room to room. There isn't any weird turn on/off thump and the heatsinks are not too hot to touch. There is a 1/4" gap at the back plate from the main chassis for hot air to escape from inside of the amplifier. I have drilled a couple holes on the bottom plate to allow a little air circulation via the back plate 1/4" gap. I started out browsing the webs for pricing and availability of fancy heatsinks. After several weeks of that, I have concluded that fancy heatsinks are expensive and not easily obtainable in small quantity and if I want to get the project going, I would have to consider alternate heatsinks. I finally decided to use the heatsinks that Wayne Sankey uses (& thus called clone of clone) because I knew that it works well per Wayne's write up. Overall, I would have to say the heatsinks turn out to be NOT the most expensive component of the amplifier. I use a 1KVA, 35-0-35 transformer with shielding from Victoria Magnetics. There isn't any annoying hum from the amplifiers even though I don't have a PI power supply. The shielding of the transformer might have contributed to that. The main circuit board is a layout done by Brian Bell. It works very well. After gathering all the parts, I have spent about four weekends building the two monoblocks. Time spent breakdown: 70% on the chassis and 30% on the electrical. This would be my first chassis building experience. I choose to build the amplifier with heatsinks pointing vertically (won't want to do it any other way) even though it took me a lot longer to build it. I have gone to Home Depot countless number of times - there must be a couple hundred screws/nuts on the chassis! The front and top plate would be fix up at a later date - may consider anodizing after polishing the sheet metal with sandpaper or steel wool. In the meantime, I'm too busy enjoying the monoblocks. I would like to thank Nelson Pass for sharing his work with us and even helping us in many ways. I want to also thank Wayne Sankey, Brian Bell, Peter Daniel and Dale Herman for answering the countless questions that I have posted on the diyAudio.com. First impression of the A2 sound. I can't exactly describe the sound like the pro does but my thought keeps going back to the analogy of video. It goes something like this. VHS picture quality is watchable but when you compared it to DVD, the picture quality of DVD has so much more detail and depth. That's how I would describe the sound of A2. Roderick Yong

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