Desktop amplifier with the TDA8920 chip

Long weekend here, so I actually had time to finish a build – nice!. For the past couple of years I have been using a cheap ready-made amp based on the Tripath TA2020 chip for my computer. However, it was always a little lacking in power for the Piega speakers I use and a while ago it started cutting out in one channel, so obviously that’s the a perfect excuse to build a new one 😉 I spotted a kit on ebay based on the Philips/NXP TDA8920 class D chip that seemed to be worth trying out and so I did. The board integrates a speaker protection circuit based on the UPC1237 IC and also, very importantly, a startup delay that means I don’t get the “boing!” startup sound from the iMac out at full blast every time I turn it on (the amp is powered from a master/slave socket controlled by the Mac).

Once again, the build recipe is simple: Get a cheap ebay kit and replace the key components if they are not good enough and/or do not fit the application. In this case, that means I have kept the PCB, the IC and most of the other components, but replaced the potentiometer with a real Alps blue and the main capacitors with some that were shorter. I used a deep hifi2000 enclosure that fits better on the desk, but this also means I am not going to win any prizes for the wiring as the speaker wires are routed very close to (= on top of) the transformer. However, the amp is very quiet and there is not enough hum for it to be an issue, even when sitting very close to the speakers.

Sound-wise this is obviously not high-end, but for the application and price it is actually not bad at all. When properly implemented the TA2020 sounds better (at least to me), but if its 10 or so watts isn’t enough as in this case it does not really work, so overall this was a worthwhile upgrade.



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