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Linear power supply for Cambridge iD100 iPod dock?


swt61

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Most expensive thing would be the transformer, probably $20-30. Everything else is cheap: the lm338, 5 diodes, a couple resistors, a pot to fine tune the voltage, and 3 or 4 caps. Probably cost about 40 bucks. You could do even cheaper if you got an ac to dc wallwort and just passed the dc through the lm338.

Or you could go crazy and build a sigma 11

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Well I was assuming 2A would be peak. But even if we use the equation on the sigma 11 site

Tj=Ta+(P*(Rjc+Rcs+Rsa) allowing a fairly warm ambient of say 40 degrees C

100<=40+(7*2*(3.3+.48+2))

100<=40+(7*11.6)

100<=121

This is using the Bergquist isolation pad and the recommend aavid onboard sink, as well as the recommended 7V over desired regulation.

So I guess you're right 2A continuous would be too much. But if it's more like 1A continuous and 2A peak then the junction temperature is only 80.6 which would be fine, and I seriously doubt something that specifies a 2A supply will be pulling 2A continuously. And you could always use offboard sinks for better cooling. The 7V above regulation is rather conservative as well.

Edit: I just took a peek at the manual and under the technical specs section it states up to 12W power consumption when charging a device, so it should never be pulling more than 1A continuous.

Edited by cobra_kai
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The battery could work but if you want any reasonable playing time between charges you would have to get a somewhat large one which not only increases price but also footprint.

If you're looking for something more elaborate than a lm338 based PS, you can also check the placid from twistedpearaudio which has been put on par with the O11. I'm not sure of it's current capabilities though, but it comes as a kit and they also sell the transformer, so you could save on shipping costs.

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So after some back and forth with Fitz, I've decided that a STEPS will do what I want, without getting too crazy. Fitz has an extra board laying around and I'll stuff it into a Hammond case and be done. Thanks for all the help and suggestions!

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