Prompted by a few recent enquiries here, plus a long term general curiosity about these amps, I've decided to go build one! They are generally regarded as easy enough to build due to the low number of components in the amp plus its all low voltage work. Reading around, the main difficulty that people experience is RF pickup/hum and these are largely due it seems to grounding issues.
The original circuit that the whole chipamp movement is founded on is the Gaincard amp from 47 labs. You can read their blurb at:
http://www.sakurasystems.com/products/47amp.html
but the gist of it all is that its a very minimalist amp, with only 9 components in the signal path, and with very short signal paths if built the way 47 labs did it. This is the circuit:
And as you will see its very minimalist indeed. There have been posts and pictures too from people who have opened up the real 47 labs gaincard:
http://dogbreath.de/GainCard/GainCard.html
Of course the rest is kinda history, the word spread about how good these amps sound (when they have no right to etc etc etc).
There are lots of options out there for how to build one of these. Its so simple you could wire it point to point. It would be easy to do on a piece of breadboard - essentially how 47 labs did it. Ebay has lots of them etc etc etc. There are also a few different chips to choose from too, but AFAIK, all are from National Semiconductor. Their LM3875, LM3886, LM4875 are the main players in the field.
I have dealt with a fella in Canada over a nubmer of years who offers a kit for the LM3875 and 4780 chips. After talking to him, I chose his LM3875 to build. This chip is meant to be the sweeter sounding of the common options, but is slightly lower power output than the others, and also reputedly to have slightly less bass. You can see his stuff at:
www.audiosector.com
and there's a review of his amp at:
http://www.6moons.com/audioreviews/audi ... patek.html
I also made a decision to do a dual mono build - just because I know myself well enough that if I didn't do it, then chances are I would end up having to retrofit the second half of the power supply later!!
Fran
