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Hi,

I'd like to do something like this, but I can't find the right kind of inductors anywhere, locally or online. All I can find are ones with 6 or more leads that are obviously for circuit boards. Anyone know where I can get a hold of some inductors like the one pictured?

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The Prince of Dorkness

Hi there,

What is shown in the picture is a transformer, i.e. two inductors coupled together. If you use the outside leads of one side of the transformer, you have an inductor.

Mouser.com is a nice small transformer source.

Marc

Thanks!

Mouser's selection is so extensive that I haven't the foggiest idea what I'd need. Any idea what frequency range I'd need to make a tone pot that cuts bass? I'm trying to create a tone pot that will make my humbuckers less "muddy". I already have the 1 meg pots I want to use, but am at a loss for finding the low-pass filtering inductor/transformer. I'd really hate to spend 30 bucks on the pot I linked in my initial post when all I want is the transformer off of it.

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The Prince of Dorkness

This is what I am using for my varitone circuits...

http://ca.mouser.com/Search/Refine.aspx?Keyword=42TL021

Marc

Good Day,

The term for a filter that cuts low hz and passes highs is a high pass filter. You can do this what a capacitor and potentiometer. it is just the reverse of the low pass filter in most guitars. Here are a couple of links to calculators that will help you size the capacitor and show you this circuit.

http://www.muzique.com/schem/filter.htm
http://hyperphysics.phy-astr.gsu.edu/hb ... ilcap.html

You may want to add a fixed resistor in series with the potentiometer. This will keep you from shorting out the signal when the pot is completely close. Adding and inductor will increase the slope of the curve but for your purpose that should not be necessary. for more links Google high pass filter.

Good luck,

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Eddie Lee

Marc,
Thanks! I'll give that a go.


Eddie,
I mean a low pass filter. In order to cut bass, I need a low pass filter on the ground of the pot. So that low freqs go to ground while highs do not. The opposite of a traditional tone pot.

A cap on a pot is just a normal tone control, i.e. it allows highs to pass to ground and blocks lows from going to ground, keeping them in the circuit. A cap is a high pass filter. I need the opposite of that, therefore, as I said, I need a low pass filter (inductor) on the wiper (ground) of the pot instead of a cap.

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The Prince of Dorkness

It depends on how you configure the circuit. A filter is named for what is passed out of the filter, not what happens inside the filter. It is true that a cap will block low hz and pass the highs.

In a low pass filter the cap is placed to ground. This will short the highs to ground and pass the lows. This is a normal tone control on guitars that roll of the highs.

In a high pass filter the cap and the resistor is reversed for the low pass filter configuration. The resistor now goes to ground and the cap is in series with the signal. Now the highs are passed out of the filter and the lows are blocked by the cap.

Here is a link to a High pass circuit and graph http://hyperphysics.phy-astr.gsu.edu/hb ... ap.html#c1

This is a link to a Low pass circuit and graph http://hyperphysics.phy-astr.gsu.edu/hb ... p2.html#c1

You can do the same thing with a inductor but it will be more expensive and the inductors that will do this will not be easily available. Caps are cheaper, more available, and smaller.

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Eddie Lee

Eddie,

Thanks, but how would a capacitance low pass filter work with a pot? I've already tried using a cap to bypass the pot, theoretically making the pot only control the bass, but it didn't work. With the pot turned all the way down to 0, it shut off all sound completely.

If there's no way to make a capacitance low pass filter attached to the wiper of a pot so that the pot attenuates lows (variably according to the position of the wiper), then it's not useful to me.

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The Prince of Dorkness

This is a link to a LR High pass filter ( the lows are shorted to ground and the highs are passed)

http://sim.okawa-denshi.jp/en/LRhikeisan.htm

Using the formula L=R/2*Fc*Pi where Fc is the cutoff Hz.

For a Fc of 160hz and a resistor setting of 10k ohms L= 9.95 henry. This is a high value for an inductor.

Here is a link to a 10h inductor. This is a big item and cost $11.74. This will carry more current than you need but I could not find a smaller one.

http://www.mouser.com/Search/Refine.asp ... or&FS=True

The RC High pass would be an easier option IMO.

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Eddie Lee

Try this. With the pot all the way open the cutoff will be about 30hz. With it all the way closed the cutoff is about 400 hz.

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Eddie Lee

Thanks so much for all your patient help. I'm going cross-eyed and seriously considering sticking my tongue in my amp's aux. output jack.

So, I looked at the schematic you were kind enough to post. Unfortunately, I don't know how to read electronics diagrams. Does that diagram mean this?:

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The Prince of Dorkness

POD,

That looks like you have it. IF the pot rotates the wrong why when you hook it up change to the other outer pin of the pot. If you want more bass cut, you can reduce the fixed resistor value, but I would not go below about 1k ohm.

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Eddie Lee

PS How did you post that picture?

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Eddie Lee

Eddie,
Thanks again for all your help. I posted the picture by making it in photoshop, uploading it to Imageshack, then using the "img" BBcode tag to put the image's url into the post. Like this:



Marc,
Thanks again for all your help too. I've ordered the inductor you pointed out to me. I want to try both ways, capacitive filter and inductive filter, and see which I like best.

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The Prince of Dorkness

Great Thanks !

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Eddie Lee

You're welcome Eddie.

By the way, here's a tip: if you have Photoshop, then before you upload a picture to Imageshack, or Photobucket, or any other image hosting site, do the following:

Open the image in Photoshop

Click "File" > "Save for web" (NOT "save as")

A new window will open in which you can slightly reduce the quality enough to greatly reduce the file size, but not enough to really be noticeable to the eye. I usually save at 90% quality.

The resulting image will be a high-compression jpeg at 72 pixels per inch (which is all most computer monitors can show anyway) and will not have extraneous embedded data like thumbnail previews. Doing this will drastically reduce the image file size, thus reducing the load time in people's browsers when they view it. I've had images that started as 1 - 2 megs get reduced down to under 300k in this way with little or no noticeable decrease in image quality (at least not to the naked eye). Images that start out at several hundred dpi, like most digital camera photos, will be MUCH smaller as a result. Even images that start out as 72 dpi will be made smaller by virtue of being stripped of their thumbnail previews.

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The Prince of Dorkness

If you are trying to make a varitone? A pot is not used. It's a rotary switch. 6 position. as far as the inductor. Gibson uses a 1.5H henry choke. It's very large. Now you can use a smaller transformer that will act as this choke. See below

Here's a schematic:
Varitone Schematics http://www.blueguitar.org/new/schem/_gtr/varitone1.gif

and to quote an old friend who has passed.

"Just get a 1.5H choke, a rotary switch, and a handful of caps and resistors, and throw one together. Or you can get one already assembled from Big D Guitars - he uses ceramic caps for vintage mojo, not my choice, but for $50.00, you can't really fault it.

You can use a Mouser mini transformer (42TL021) primary for the choke, and poly caps, metal film resistors, etc. for a nice clean quiet modern sound, or get an old radio choke and use those ceramic disc caps and carbon comp resistors for maximum oldschool magic (and noise).
Torres Engineering also offers their "Famous Guitar Kits™" version, and of course, you can get a Gibson, if you're willing to part with a lot more cash. LoveKraft "

Hope this helps
MK

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I'm outside looking in, just farther from the window than most.

Thanks, but no. I'm not trying to make a Varitone.

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The Prince of Dorkness