Simple non-intrusive voltage divider cables

[pfhor]

I thought my first voltage divider cables turned out nicely so I made a newbie-friendly step-by-step guide on how to make them for those less DIY-inclined.
For those unfamiliar, these cables will let you lower the voltage produced by your pads. Some pads have too "hot" signals for Megadrum to handle, which is where these come in. The trimpots will let you adjust the voltage of both head and rim to best value (or leave it unchanged).



Just a test fit on my (unfinished) module. Pedal-cat approves.

You'll need, per cable:

• 1 tripad stripboard cut to 12x3
• 2 473 trimpots
• 5 cm 10mm heatshrink tubing
• 1 5mm LED (just for the leads)

All of which can be picked up in large quantities for pocket change on sites like Ebay. I just used what I had laying around.



Cutting the board might be the most work, depending on what tools you have. Scoring & snapping, hacksaw, dremel or any other kind of cutting tool will work but might ruin the neighbouring pads. I'm lucky enough to have a scrollsaw that lets me cut inbetween the pads. Just make sure you leave every hole intact.


Steps:

Cut the cable where you want to insert the divider. I went with 6 cm from the module end connector.

Starting with the short end, strip 2 cm of insulation.

Twist the ground threads into a wire and cut red and ground to half length. Some cables have a lot of ground threads, make sure it doesn't get too thick by cutting off any excess.
Trim the ends of red & white.


Make cable clamps by cutting the leads off of the LED and bending them over a small screwdriver or similar. I used my small round file.


Insert the wires into their respective holes and install the clamp over the edge of the cable.

Code: Select all

... ... ..G ..C
... ... ... ...
... ..W ..R ..C


G = ground, W = white, R = red, C = clamp.

Apply pressure to the clamp and bend the feet. Finish off with a light squeeze from a plier.


Now for the other section of cable, prepare the wires like before except reverse the lengths of red and white.

Slide the shrink tubing onto the cable. I forget this almost every time I'm applying sleeving to something. It's never fun having to disassemble something you just nicely put together.

Install the wires and clamp. Make sure the wires can twist around the legs of the trimpots (this might require a bit of fiddling, pushing the wires around with a thin object helps).

Code: Select all

C.. .G. ... ...
... .W. .R. ...
C.. ... ... ...


G = ground, W = white, R = red, C = clamp.



Install the trimpots and bend the legs. Bend the ground leg of the first trimpot backwards so that it bridges the gap between the two strips.

Code: Select all

... TG. T.G ...
... .WT .RT ...
... T.W T.R ...


Solder.


Place the heatshrink over the trimpots and press down on the edges of the heads to leave an imprint. Use a precision knife to cut out holes.


Push the heatshrink down around the trimpots and apply heat from a lighter to shrink it.


Have a beer.


Notes:

I have two types of cables, red/white <-> tip/ring were reversed between them.
I usually use smaller heatshrink on the ends of larger heatshrinks like this for a nicer look, but thought it was detrimental in this case.


Parts

Here are some quick Ebay links for the parts:

473 trimmers
10mm heatshrink
5mm LEDs
TriPad Stripboard A bit hard to find on Ebay it seems. I bought mine locally (Clas Ohlson for any scandinavians).

[jackiecorn]

Thank you very much for the detail tutorial, would help a lot of people.
I have a question regarding "hotness" I want to ask but don't want to open a new thread:
I know the larger the piezo the hotter the signal, so between two sizes: 35mm and 27mm
If I were to add a voltage divider(pot) to my cable, will it be a better choice to have 35mm piezo+higher resistance or 27mm piezo+lower resistance? (tuned to the same signal range)
I mean in terms of accuracy and reliability, or if it matters at all..

[pfhor]

Replying to this thread after many months, but, to quote Dmitri, that has nothing to do with this thread, start a new one. Real answer: I have no idea.

Anyway, I've seen a couple people try to follow up on my tutorial with varying results, if anything is unclear just ask in here. It does take a bit of detail work since the size you're working with is supposed to be small or it wouldn't fit on a cable, but the basics are very simple. But going through it again now I see some parts might be unclear or seem overly complex, so feel free to add to it or ask questions if you do end up using the same design.