GGG 6 band eq

[mars_bringer_of_war]

http://www.generalguitargadgets.com/pdf/ggg_eq6.pdf

There are a few discrepancies in the parts list and the layout for this project, notably in resistor values. Can anyone offer some insight as to which is correct, the layout or bom?

[Dean Hazelwanter]

If you give me some specifics I'll be happy to take a look.

[mars_bringer_of_war]

Thanks for the reply.
In the bill of materials, a 47k and two 1M resistors are listed, but don't appear in the diagram or the schem. Moreover a 100k is in the diagram, but not in the bom (or the schem).
Just a bit confused. 

[kvb]

I built this and followed the schematic for values, parts, etc.
I posted a build report. no pics yet.
I don't recall having a problem in regard to parts . . .

. . . except that the film caps for the 2 bass frequencies would not fit on the board - way too big. Just a heads up.

Later, I solved the problem by getting some SMD caps (mouser). I soldered leads onto them, put them in, and then covered them with some heat-shrink. I shielded the input as well, but there didn't seem to be any difference in noise. It is as quiet as a used parametric that I scored recently.

[Dean Hazelwanter]

Ok

There are some errors in the BOM, so use the board layout and schematic as correct.

The 100K resistor on the layout is on the schematic - it's the 1st resistor that appears after the 1st 10uF cap after the input jack.

kvb: - guess I got lucky - I had some little film caps that fit for the bass frequencies, so that's what I used for the layout.

Hope that helps, and that you enjoy the project!

[mars_bringer_of_war]

Yep, I see that 100k on the schem now, sorry about that.       
So, I'll just use the layout.

Those (relatively) larger value caps are available in smallish physical sizes in film. I've got .22uf, .47uf, and 1 uf boxed film caps that are just about the isze of a 16v electrolytic, so I know they're out there.

Dean, many thanks for your help.

[msurdin]

Is it possible to use a resistor or cap instead of the pots to have an assigned frequency?

Thanks

Matt

[Dean Hazelwanter]

Hi Matt,

Sorry, I don't understand your question - can you elaborate?

[mars_bringer_of_war]

Is it possible to use a resistor or cap instead of the pots to have an assigned frequency?

Thanks

Matt

Do you mean using a fixed resistor to have a preset boost or cut for each/any of the bands?

[msurdin]

Well instead of having the pots or faders to change around the eq have it fixed inside. All the enclosure would have outside is the power, 3pdt, vol control, and led.

I dont want to have to worry about the settings on my eq to change.
As an example, on the boss ge7, I use that with the 2 right and 2 left all the way up. The 3 middle are up a quarter of the way. The vol is the only thing i move. so What I wonder is if there is a part to put on the GGG eq project to replace the pot so the setting i want is permenent.

Thanks

Matt

[RickL]

It absolutely can be done. Think of a pot as two resistors in series. The wiper is where they connect. A 100k pot with the wiper in the middle (assuming a linear pot) is like two 50k resistors connected in series. The connection is the wiper, the two free ends are the outside lugs of the pot. Similarly if the pot is turned up exactly 1/3 of the way it's like a 33 1/3k resistor connected to a 66 2/3k resistor. And so on.

Figure out how you want the pots set and replace them with the nearest standard value resistors you can find. You  just have to get close, for instance in the second example a 33k and a 68k would be fine. The easiest way to do this is to temporarily connect pots, set them the way you want them, then unsolder without turning the shaft and measure. Don't try to measure without disconnectling at least two of the wires or you could get false readings due to interaction with the rest of the circuit.

Another option is to use trim pots in place of the full size pots. Mount them on a bit of perfboard and wire them exactly as you would the full size pots. This method has the advantage of letting you change the settings without having to unsolder and resolder new resistors. You could even get clever and mount them in the box so you could access them through small holes.