Thaddeus Smith Posted August 21, 2014 Share Posted August 21, 2014 I'm running a small class D amp (TPA3116d) from a HAM power supply that outputs ~12v/7A and using only a fraction of the power. I'm planning to add a raspberry pi inside the chassis with an onboard DAC - which only needs 5v/2A total. I'd like to consolidate external cables if possible - can I run all of that from the same 12v/7A power supply, provided I use an appropriate DC step down convertor for the computer? My instinct says yes, but I don't want to accidentally fry components by not asking smarter people first. Quote Link to comment Share on other sites More sharing options...
minermark Posted August 21, 2014 Share Posted August 21, 2014 Id say yes, plenty of power, however the only part that has me baffled is the "Step down converter"? to the computer? Are you feeding the "Line in" or USB? Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted August 21, 2014 Author Share Posted August 21, 2014 The computer (raspberry pi) runs off 5v/1-2A power supplies through a micro-usb cable. Basically any standard phone charger or usb port. The power supply i have for the amp puts out 12v (which is what the amp needs) so I need to step it down to 5v for the computer power. That part I have figured out, I just wasn't sure if there was some potential issue unknown to me by running both devices from the same DC 12v power supply. I just want one cable going from the amplifier chassis to the 12v power supply and then i can split it off as necessary inside the chassis. Like I said before, my instinct is leading to "yes it'll work just fine" but I always get extra paranoid when dealing with power. Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted August 21, 2014 Author Share Posted August 21, 2014 Are you feeding the "Line in" or USB? there's no line in. the computer is hardwired to the network over ethernet and streams FLAC files from my NAS, parses it through the I2S connector into the DAC module, and outputs directly to my amp via onboard connections. I'll post pictures once I get everything installed and wired up. 1 Quote Link to comment Share on other sites More sharing options...
minermark Posted August 21, 2014 Share Posted August 21, 2014 Ok, got ya, id say do it. Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted August 21, 2014 Author Share Posted August 21, 2014 basically, I'll use something like this and just chop off the usb end and wire directly. Made to step down from 12v to 5v in RC cars, planes, etc. http://www.hobbyking.com/hobbyking/store/__15212__hobbyking_micro_ubec_3a_5v.html 1 Quote Link to comment Share on other sites More sharing options...
minermark Posted August 21, 2014 Share Posted August 21, 2014 7 amps is a lot for what your drawing off it, plenty of power. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted August 21, 2014 Share Posted August 21, 2014 Like I said before, my instinct is leading to "yes it'll work just fine" but I always get extra paranoid when dealing with power. I agree with Mark. As long as the total amperage required doesn't exceed the amperage output of the converter you should be fine. 1 Quote Link to comment Share on other sites More sharing options...
Schu Posted August 22, 2014 Share Posted August 22, 2014 Man... you guys like to do things the hard way Quote Link to comment Share on other sites More sharing options...
oldtimer Posted August 24, 2014 Share Posted August 24, 2014 Quote Link to comment Share on other sites More sharing options...
MikeFord Posted August 24, 2014 Share Posted August 24, 2014 What is the point in using the power from the 12v supply for the raspberry as opposed to using two supplies, one for the amp and one for the strawberry and dac? Putting two supplies in series means the input to the raspberry supply is going to have some modulation from the operation of the amp. What sort of sensitivity to input power variations does the DAC have? Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted August 24, 2014 Author Share Posted August 24, 2014 A couple of reasons - the amp and rasp pi both reside in the same chassis, so it reduces cable clutter by only routing the one power cable into the case. From there I'm using a terminal block and splitting off the power to the amp and UBEC+rasp pi. And the linear power supply I'm using is far better than the dinky little apple charger I'm currently using to power the rasp pi. No clue on the dac input power variations. It mounts directly to, and pulls power from, the rasp pi and is built solely for this application. Firstly, I wanted to make sure I don't melt anything by hooking it all up. If it sounds like crap by implementing in this manner then I'll rethink the strategy. I definitely appreciate the additional questions and technical considerations - it's stuff like that which I didn't even know to ask. 1 Quote Link to comment Share on other sites More sharing options...
minermark Posted August 24, 2014 Share Posted August 24, 2014 A couple of reasons - the amp and rasp pi both reside in the same chassis, so it reduces cable clutter by only routing the one power cable into the case. From there I'm using a terminal block and splitting off the power to the amp and UBEC+rasp pi. And the linear power supply I'm using is far better than the dinky little apple charger I'm currently using to power the rasp pi. No clue on the dac input power variations. It mounts directly to, and pulls power from, the rasp pi and is built solely for this application. Firstly, I wanted to make sure I don't melt anything by hooking it all up. If it sounds like crap by implementing in this manner then I'll rethink the strategy. I definitely appreciate the additional questions and technical considerations - it's stuff like that which I didn't even know to ask. Thad, hows it going with the project ? Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted August 24, 2014 Author Share Posted August 24, 2014 waiting on the UBEC to arrive. Still need to order the DAC. fiddling with some wifi configurations on the raspberry pi. otherwise I have the case all laid out and wired and ready for use. Cornwall components are transferred to the new cabinets. Probably another couple of weeks before I'm ready to fire it up and play - both for part acquisition and it's too damn hot to use my office where the system is located (it's part of my detached garage). So I'm enjoying my KP-201's in the house for now 1 Quote Link to comment Share on other sites More sharing options...
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