WSG build, possible problem

[creynolds77]

I built the WSG with the PCB from mfos and it makes wonderful sound, unfortunately it seems the pots range is not correct. From the middle position on the pot to all the way clockwise the range sounds great a nice big sweep from low to high. Counterclockwise from center only mildly adjusts from low to just a little bit lower. I put my multimeter on it and it shows that I am getting almost 1M ohm at the center position on the pot.

On the case wiring diagram I saw that there were wires that ran from the center lead on the pot to the one beside it, rather than run little jumper wires, I soldered the two leads together. This seems to me like the same as running a jumper wire, so if this is my issue, please tell me .

http://twitpic.com/4er4x9
http://twitpic.com/4er58x

[jordroid]

Hello and welcome!

Firstly, you are correct that if the wiper (center lug) and one end of the pot are connected then you can consider them electrically the same, any spot in the circuit connected directly with a wire or jumper or solder can be considered a single node and it shouldn't matter where you make a connection to it.

In this example, a pot is being used as a variable resistor, and you actually do not need to solder the wiper to the other end of the pot, it will function exactly the same with only two terminals used. Ray probably wires them together just to give you another lug to use as a terminal, it gets crowded jamming a bunch of leads into one lug. Apologies if that is confusing or unclear, the point is, the picture you linked looks ok.

It sounds like the issue could be that you have used a log pot, instead of a linear one? It's the first thing that comes to mind, and would result in what you describe. It's also an easy fix (replace it with a linear pot) , which is always nice.

Log pots often have the letter "A" somewhere, it may say "1MA" for instance, for a 1 meg log pot. Linear pots will often use the letter "B" in the same way. The terms "log" and "audio" are often used interchangeably, both meaning a potentiometer with a logarithmic response.

They don't always follow that standard though. If you measure the pot out of circuit (no wires soldered to it, one probe clipped to the wiper, the other probe to either of the other terminals) a linear pot should read about half of the total resistance when the wiper is in the middle position, a log pot will read either a small fraction of the total resistance, or a large fraction with the wiper in the middle, depending on which side you clip your meter to.

If that's not it i would be happy to try to help you track down the issue, the WGS was one of the first things i built and it's tons of fun. I let a friend borrow mine and it never came back

regards,

jordan

[creynolds77]

[jordroid]

Cool, an easy fix, and the log pots will come in handy some day. My favorite mistake (iv'e done it more than once) is ordering the pots with a bunch of evenly spaced detents, it makes them quite unsuitable for anything requiring fine resolution.

cheers