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41Hz.com's Amp 1B

This is a Class D ("Class T") power amp from 41Hz.com. It is the Amp1-B which is actually just the Tripath eval board. The only thing that 41Hz does is swap out a few caps with slightly upspec'd versions. I swapped out the same caps for some higher spec'd ones as well as a few others.

The wood is walnut finished with some "Tried and True" oil. I left the aluminum unfinished, at first out of lazyness, but now as I kind of like the industrial contrast with the wood.

The power supply has 20 x 1000uF Panasonic FMs and is based on a design by CarlosFM at DIY audio. On the rails are 1500uF FCs and 0.1uF film and foil bypass caps. I like the Dayton brand for this as they are dirt cheap and seem to work quite well. For these larger caps, Tripath suggests 220uF caps which is anemic. 41Hz supplies cheap 330uF caps, which are also anemic. I tried 470uF Muse caps at first (see the breadboard pis below) but really the amp needed more. The 1500's were what I had around and seem to work well -- notice that they don't fit on the board so well.

I also replaced the supplied input caps (Panasonic FCs) with Blackgate 4.7uF N series. Obviously, film caps would be better, but I used the Blackgates to fit them on the board. I am told, though I didn't measure to verify, that the input to the chip is biased up by a couple of volts thus requiring input caps.

Last, here it is on breadboard before going in to the case.

My impressions are that for the $100 or so it takes to build this amp, it is a great deal. I prefer it to the Gainclones I've built for most things, but it can be a bit sharp and tizzy on the top end. Case in point: Nico Case is unlistenable with this amp. Acoustic music, however, is often very pleasant.