Flat cable, any good for stompboxes?

[bioroids]

Hi!

I'm wondering about that flat cable (like the one connecting the hard drive on your computer). It would be cool to use it in pedals, for example, connecting the effect board to a separate board with all the pots. But I don't know if running all that lines in parallel is such a good idea 

How much coupling can happen between adjacent cables? They are supposed to carry digital signals well (square with 5v, or 3v amplitude), but I know digital signals can tolerate an amount of noise than an analog signal can't. I read somewhere they have like a 7% crosstalk, which is a lot, but we are talking digital signals in the MHz range, so how can it apply to analog audio signals? and what about that LFO rate pot which receives a big square signal?

Probably a good selection of which signals go to which cables can help avoiding issues, maybe using extra ground wires between some too.

Any input regarding this is welcomed!

Regards!

EDIT: I found very good info here http://www.diystompboxes.com/smfforum/index.php?topic=45252.0

Miguel

[Paul Perry (Frostwave)]

Most of my stompboxes have flat cable linking the two boards (one board for sockets & power supply, the other larger board has the pots on it & the main circuit).
I have every second wire in the cable grounded.

[Ronsonic]

If you've got concerns or your layout encourages a cable layout that you think will be trouble, like having input and output lines on adjacent wires, you can alternate signal and ground lines for isolation. Any added capacitance will be trivial.

Ron

[bioroids]

Thanks Paul and Ron!

That was the answer I was looking for  !

Miguel

[Mark Hammer]

Hold up at second base there, buddy!

Not all ribbon cable is created equal.  I too have pedals where controls/switches are installed on a daughter board connected to the mother board via a ribbon cable.  But THAT ribbon cable is made of much sturdier wire than what is normally found on cast-off $5 IDE or floppy drive cables.  The risk of fracture in that wire when it is stripped and soldered to a board is much higher than what one is likely to find in the average pedal.  You CAN use it, but I would strongly urge you to also use some sort of strain relief to avoid the heartbreak of fracture.  That could be as simple assome hot glue applied to the board/wire junction.  If you want more support for this idea, just try to imagine what you would have to go through if you had a 16-lead ribbon and the 9th wire in from the outer edge fractured at the board.  It would require desoldering the entire thing and starting over again with stripped leads.

Stiff wire and strain relief is the only way to go.

[bioroids]

Yes, and there are different AWG sizes for flat cable too.
I wasn't thinking of soldering it to the board, but rather using IDC connectors "Hard Drive Style", like Paul uses on his pedals. This is much easier to do (with the crimping tool) and also allows the boards to be disconnected at will, and the cable changed in case of failure.

I can imagine what a pain must be to replace that 9th wire! 

Luck!

Miguel

[sta63bmx]

I am a huge fan of the rainbow-colored ribbon cable like that.  I think it makes packing everything in there easier.  But I agree, stranded wire can be troublesome if it gets bent back and forth a lot.  You have to be really careful when you solder it to make sure that you hit it really quickly and try to use a minimum of solder so it doesn't wick back up into the wire and make it brittle.  Whenever that happens, it's game over.  I have not made my own layouts with headers and disconnects, but I think that would be pretty cool.  I just figure that since I'm soldering bare wire ends to the pots anyways I might as well do it on both ends.  If I'm working with weenie wire on perf sometimes I'll bring the wire up through an adjacent hole and down through the solder hole and then solder it so I've got some strain relief.

Conclusion: I have built a few boxes with that kind of cable and I really like it.

9V Electric Mistress (Markus' layout, thanks!)


Walshinator ("Two-channel" TS-808 clone) (Tonepad layout)


BSIAB2 (GGG Layout)


I usually at least put all the pots on one thing of ribbon cable.  It's really convenient.  And in places where I only have a couple wires I still like how you can have pairs of wires neatly joined.

[Barcode80]

where do you usually get that rainbow wire?