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made up a 4 channel backplane

A project log for DSP Field Mixer Recorder

USBmidi, bluetooth app controll 8 chan portable DSP mixer.balanced audio IO,phantom power,flexible routing,ISO recording. networked Timecode

ben biles 06/05/2017 at 17:465 Comments

I made up this 4 channel back plane , wasn't worth playing around with veroboard, too much work ! you can see the digital sections ground plane partitioned from the analogue on the right side of this pic. I put the new power supply in a plastic case ! 48v phantom can damage things :) there was 2 small errors on the board but managed to cut a trace and bodge wire.

This board is 4 preamp , 4 x balanced line driver and 2 x stereo headphone driver. I'll make an 8 channel version after I get the recorder app wired up and working .

Discussions

ben biles wrote 06/06/2017 at 02:25 point

Yer , error in Mosi Miso , they should be in a chain and i had them in parallel , 5 min fix with a engraver drill and bodge wires and got it working. The preamp cards should have DC blocking caps on there side so the cards can be closer together so hopefully when I make that change I can make an 8 channel backplane :) I saw a great trick on another board design where you have axial capacitors with the body of the capacitor sitting in large hole cut into the pcb! going to give it a try :) should be able to get those preamp cards quite close together that way. 

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Francesco wrote 06/06/2017 at 10:15 point

Why don't you simply use smd aluminum capacitor instead? Are they worst for any reason? They are generally quite small...

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ben biles wrote 06/07/2017 at 05:48 point

do u know of any low profile 22uf 65v smd caps? My dc blocking caps Thu hole are 47uf  65WV but I think 22uf would be OK. Current ones are 11mm high but I think if I put axial ones in a hole in pcb I could get that down to maybe 2mm a side..  are you thinking of pannasonic smd? There 11mm high to I think? I'm blocking phantom power dc which is 48v so I need 65v caps or more... 

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Francesco wrote 06/07/2017 at 08:35 point

No ok, watching your photos, i thought your caps were bigger, 11mm is already quite small and you're right, smds are same hight. Nevermind, yours is the best idea!

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Francesco wrote 06/05/2017 at 22:21 point

This looks amazing!

I was looking on the schematic of this backplane yesterday (my approach is different and i was just curious) and i wanted to write to you cause i thought there was an error on the shared SlaveSelect line... too late I think, unfortunatelly :( Can't wait to hear the video when completed :) 

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