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A Combined DAP and Amp (Sansa Clip+ and cMoy)

post #1 of 2
Thread Starter 

Hello everyone, I just wanted to float out an idea that I've been having and see what advice people could give me.


Anyway, the background is that I'm a Product Design Engineer and skint student, who enjoys making things difficult for himself...





I want a reasonably affordable, portable system for listening to music via headphone, which includes an amp. So the basic requirements are; a DAP, an amp and a pair of headphones. So far so simple. But carrying around all three items, ensuring they are charged etc seems (slightly) awkward and unnecessary, so I want to streamline things, whilst retaining performance.


So the plan is to try and integrate the DAP and the amp into one housing if possible, whilst retaining a reasonably small bulk. (My course involves an art school component along with the engineering so I also want to make things look pretty :rolleyes:)





As I mentioned before, I'm hoping to keep things reasonably affordable. My budget for the DAC and amp is under £100, however I do have free access to an extremely well equipped workshop through my course, so I will try and use that to my advantage.


So, a bit of research has led me to select (provisionally) the following components:



Sansa Clip+ as the DAP (will be Rockboxed)


cMoy Amp (probably the kit from JDS Labs, unless the design require large tweaks)



The headphones this system will be driving will be Aiaiai TMA-1's. (Not included in the budget, obviously!)





Right, so far hopefully everything makes sense. At first this project was simply going to be making a nicer case for the Clip+, but as you can see things have escalated somewhat...


I would like to combine the DAP and the amp into one housing. The Clip+ and cMoy are both small, and should hopefully fit into a housing no larger than 110mm x 50mm square. For the housing I had in mind a CNC milled aluminium case, or possibly a 3D printed one. (This is where the university workshop comes in useful!)


BUT, as I'm sure you have realised, the cMoy would only fit into such a footprint without the 9v battery most people build it with...


So, my ideal solution would involve incorporating a single rechargeable battery that powers the Clip+ and the amp simultaneously. This would be the most streamlined option, requiring only one charger and no regular replacing of dead batteries. The reasonably large footprint should (I hope) permit an adequate battery to perform both functions with decent life. (What I currently have in mind are Li-ion phone batteries...)


However, the Clip+ battery is rated as 3.7V 290mAh, and the cMoy generally is used with a 9V.


This is the main problem that I can see right now.


As far as I know the Clip+ would require a 3.7V battery to function, hence this cannot be altered. I would have to find out the minimum required voltage to operate my headphones with the cMoy, but I suspect it will be above a 3.7V supply.


Could a boost converter be incorporated into the cMoy circuit to drive it reliably without noise or interference? Any comments, constructive criticism or advice on any part of this project that you can provide is welcome. :)





Thanks for reading,




PS: I am aware that this might turn into a LOT of work, whilst solving a "problem" that doesn't really exist. Some people might call that pointless, but hey, I have to do something with my summer! :darthsmile: 

Edited by whoiszed - 5/2/14 at 1:16pm
post #2 of 2

DAP already have purpose designed op amps that drive low Z, high sensitivity cans better than most easy to apply op amp choices you see in a simple "cmoy"


the Aiaiai TMA-1 are low Z 32 Ohm, this means the 105 dB sensitivity is almost certainly re 1 mW - so the Clip+ internal amp should already drive them to ~113 dB SPL peak at clipping


113 dB SPL  could be enough for most listening scenarios - with enough dynamic headroom for even very dynamic 20 dB pk to ave recording at any safe for all day average SPL level



if you want to drive high Z and/or low sensitivity cans a higher V is needed - there are lots of DC-DC converter solutions - vary in efficiency, cost, design difficulty - this is a pretty low power application by industry standards


simple would be to just use a linear regulator to drop the V from a 9 V to provide USB power to the Clip

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