July 28, 2014 1 Comment
These “little helpers” are small supporting boards I have developed for my various audio projects. I have a few different ones and I don’t think they are really “big” and sophisticated enough to warrant a post for each one so I’ve decided to lump them together in a few groups instead.
What is it?
The first collection is PCBs for mounting Alps (and a few other types, including the Noble I have used in some of the pictures :) ). Included are boards for different types of potentiometers namely stereo without motor and quad with and without motor (i.e. Alps types RK27112 and RK27114/RK27114MC).
For the unmotorised version there are two variants: “Preamp” groups input and output terminals together and “Breakout” groups the individual decks of the pot together. The “preamp” version is used when you want the signal to flow through the pot (such as in a pre-amp), whereas the “breakout” version is used when you want to insert the pot into an existing circuit, i.e. for wiring an off board pot to an amplifier PCB that has onboard space for it. This distinction is mainly to help simplify wiring – unless the circuit has a really strange design with respect to grounding, you can of course use the boards interchangeably.
How big are the boards?
Small… I don’t want to list them all here. The biggest board is the quad motorised which measures 3.5″ x 1.75″ (app. 89 x 45 mm).
What is the status of the boards?
The boards have been tested in v1.0 and for a couple I made some cosmetic changes, including changes to the footprint of the motorised quad pot, to upgrade them to v1.1.
Does it use any special/expensive/hard-to-find parts?
Mostly there’s only one real part on the board and that is the pot itself which can be a bit expensive, so yes, I guess so :D
Anything else I need to know?
- The stereo boards have a four-hole footprint to fit various pots that use that configuration, but the last set of pads isn’t connected to anything so will not work directly with a loudness tap.
- The various quad boards have all holes in the same places so the motorised and unmotoriseed boards can use the same chassis footprint (even if of course the unmotorised board is smaller)
- The “preamp” style boards have a ground plane and a ground pad that can be used if you grounding scheme requires the shaft of the pot to be grounded. Use a piece of wire connected from the ground pad to either one of the screws on the back of the pot or soldered to a ring terminal wedged between the pot and the chassis.
- On the motorised quad pot the shaft is connected electrically to the solder pins for the motor housing, so if you want to ground one of these you only need to connect a small jumper on the underside of the board from one of the housing pins to the ground pad – no messy wiring needed.
- The eagle footprints for the quad pots are not “official” but ones I made myself by chopping up the stereo footprint. They work fine, but they probably aren’t the last word in accuracy and the holes for the housing pins could have been done more elegantly…
Download design files here
Note: Always read the “intro post” for additional important information about my designs.
As usual, please remember to consult the manufacturer’s datasheet as well.
EDIT July 28th 2014: Added pictures (which I stupidly forgot when I posted this…)