m00dawg Posted September 11, 2011 Report Share Posted September 11, 2011 Originally I was going to make one large EuroRack style board for all my outs on my rackmount MB-SID. But I got to thinking it might be more versatile across projects to break it up into a modular design and would make it simple enough I could probably etch and drill my own boards without it being a huge pain or could just order a bunch from BatchPCB or even Advanced Circuits probably for cheap. The board has an audio in, mix in, and mix out. Audio in goes into a 1/4" TRS jack. The audio out from the jack is then run through resistors and combined with mix in to a mix out. The idea being that I could use some clever headers to link the modules together, ideally without needing any cabling except for the audio in and the final mix out (which would go to my op-amp module). The boards would be supported by the outside nut on the audio jack. Included is the current board layout - not much to it, really. The right-angle headers probably need to be more thought out since I want each board to be as close as possible, ideally even touching each other. Either way, the interconnect should be simple and avoid having to use cabling, so I was thinking of some sort of male/female coupling of some sort. All the headers have a GND pin but, for linking them together, I was only going to connect GND to the left-most audio jack and have it run through the chain via the mix-in / mix-out connections (to avoid ground-loops). Am I doing it right or does anyone see anything wrong with this? The MB-6582 passive mixer design generally worked for me without much fuss and so I'm using basically the same design. I figure I can compensate for the low volumes via the op-amp. If I wanted to do serious recording of each channel, I can just plug directly into that channel to bypass any downsides of the passive mixer design. Quote Link to comment Share on other sites More sharing options...
m00dawg Posted September 11, 2011 Author Report Share Posted September 11, 2011 Attachment fail :) Quote Link to comment Share on other sites More sharing options...
TK. Posted September 11, 2011 Report Share Posted September 11, 2011 Clever! Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
m00dawg Posted September 12, 2011 Author Report Share Posted September 12, 2011 Thanks TK! Means quite a bit coming from someone such as yourself! I thought I would check to see how much smaller I can make things using SMD resistors and was able to squeeze quite a bit of space. The GM5 and MBFM projects taught me not to be scared of SMD and, in this case, it's just resistors so I think that should be pretty easy to do. I did undersize the board a bit near the headphone jack - the board won't be flush with the size of the case this way and I'm not sure if that's a good idea or not (should save me a tiny bit from BatchPCB doing it this way). Still need to figure out a good solution for linking them together but I"ll dig around the Mouser and Allied catalogs tomorrow to see if I'm on the right track there. If I can find right angled female connectors I would be all set. The idea is to avoid having to use ribbon cable or wires of any kind and just rely on headers. Quote Link to comment Share on other sites More sharing options...
m00dawg Posted September 12, 2011 Author Report Share Posted September 12, 2011 Yet another version, this time using only 1 layer and uses DIL headers for the Mix Out. There is no Mix In because that is no longer required. All I have to do is use ribbon cable and compression-crimp terminals along the cable for each stereo out jack. In this way, one long run of cabling is used instead of having the mixed audio through multiple connections in the chain. That is also what made the board design simpler. I was tossing and turning last night not being able to sleep and one thing I thought of was to mount the jacks on the bottom of the board instead of the top. That way the board sits on the jack instead of hangs off of it. It also means I can put pretty silkscreen messages on the top of the board :) This one is now easy to etch at home as well, though I would still prefer to have them made by a fab house. This way I can at least make an actual prototype at home, though. The tolerances are a bit small - Eagle's default DRC check was complaining a bit about the pads and traces being so close to the board edge but they aren't critical such that if some gets slight cut it shouldn't be a bit deal. Quote Link to comment Share on other sites More sharing options...
nebula Posted September 19, 2011 Report Share Posted September 19, 2011 A quick thought: double-check how close to the jack you can put the headers. The jack's housing may obstruct whatever receptacle you try to connect to the header. Quote Link to comment Share on other sites More sharing options...
m00dawg Posted September 19, 2011 Author Report Share Posted September 19, 2011 Yeah that's what that extra box at the bottom is - that's the plastic bit that juts out from the audio jacks I've found (which are similar to the ones Wilba used on the MB6582, Sammich, etc.). I was going to mount the jacks on the opposite side of the headers so that I only have to worry about the pins jutting out on the short side. Since then, though, I've gone back and forth on moving to a mono solution which will reduce the pin count by a small amount. Due to way I'm now envisioning wiring it all up, I'll likely also use 90 degree pin headers and mount them off the edge of the board so hopefully I can further avoid any gotchas on the jack length. Quote Link to comment Share on other sites More sharing options...
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