Friday, July 19, 2019

3.5mm Breakout Board--No More Sequencer Flipping!

Hello again! I don't work for these guys and here's a plug for what I think is a very good and affordable (not DIY) sequencer:

It's an Arturia Beatstep Pro. I have used all sorts of sequencers, from cheesy/crappy/cheap to homemade to buggy to the really high end ones, and I go back to the Beatstep, it's extremely affordable for what you get, surprisingly well made, and has best of all, has awesomely musical "swing"settings.  Does it do everything you can think of? Of course not. But for $250 or so USD new in the box, it's a damn amazing bit of kit.

So what is so DIY about this? (Hello?)  Nothing yet--Go ahead--build a better sequencer for $250--when you do let me know and I will most-definitely post it.

By George no sequencer has everything! Not a feature, a bug: all the Beatstep Pro's 3.5" jacks are all on the back. That makes plugging this sequencer into other modules, at least in my rack, a bit of a pain--lift it up, turn things over, plug in your patch cables, wiggle the cable to see if it's in all the way, etc.

DIY to the rescue!

To connect the front TS to back, solder jumpers in the box in the middle. The remaining pads are for whatever else I might think up for this PCB....

The PCBs used in my prototype are super simple--it's 10x Switchcraft 35RAP2CAV 3.5" PCB mounted jacks mounted end to end, 5 per side. Two PCBs make 10 front to back connections good to go, ready to plug into whatever 3.5 gizmo you have in your rack, for easy front panel access.

Note that I had to create the eagle device for 35RAP2CAV for this (how to do create new parts in Eagle is posted here), I couldn't find it on the net, and it worked. Anyone interested? I am happy to get you the Eagle part description. Comment below.

The 35RAP2CAV is a useful jack for all sorts of DIY, solidly built, not too expensive--I find myself using them more and more. The jack has a switch built in, which is wired up on my breakout board, but not used in this application.

For my Beatstep Breakout board: here is what I came up with so far:

The front panel, which now has p touch labels, will be, after a shakeout and some more noodling, replaced by a 2mm thick frac panel from Front Panel Express.

Cables used to connect from the back of this panel to the sequencer are 6' Euro color thin patch cables, I bought them from Modular Addict, here.

The only hitch, to get everything to fit I had to Dremel off about 1/4" from the front of the PCB.  Oh well.  Maybe next run I'll fix this, but it wasn't hard to just cut off a bit of the PCB. UPDATE: easy fix. Change the Eagle's DRC rules to match JLCPCB's requirements. Turns out Eagle default DRC is much more conservative about how close a trace can be to the edge of a PCB vs. what JLCPCB supports. I figure a lot of other PCB makers are the same. 

Beyond that, this is another "Simple as it can be" sort of project.

UPDATE 9-26-19 I created another version of the same board, with 3x jacks per side instead of 5x. Since I have 6 more cables to run for this project.  Why not?  

You can get Eagle files, PDFs etc. for the breakout board on my website, go here. If you modify it (use different jacks, more jacks, less jacks, whatever) please let me know in the comments below. I will probably cook up variations myself and post more down the road.

OK back to the studio! Now that this breakout panel is mounted to my frac case I can get clocks, CV's etc quickly, no more having to flip the sequencer around! Yeh!

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