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Post by axekicker on Oct 2, 2010 0:24:01 GMT -5
Does anyone know how this works or how to make one? It sounds cools, and I just bought one, but I'm sure either Wolf, Newey or Sumgai can make one of these in their sleep. It's a rotary mid-shaper. Take a look: www.stellartone.com/index.asp
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Post by ashcatlt on Oct 2, 2010 16:30:20 GMT -5
Ummm... Whataboutme?
I haven't seen anybody talk about that exact circuit. Doesn't really look to be inductor based, but it's hard to say. When you get yours you'll take some pics, maybe some meter readings, and we'll see what we can't deduce.
Oh, and sound samples. We'll want sound samples.
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Post by ashcatlt on Oct 2, 2010 16:39:15 GMT -5
Okay, googles it. This page says that instead of varying the resistance before the cap, it changed cap values. That's pretty easy to do. Where it starts to get expensive is mil-spec rotary switches and smd caps which are not expensive themselves but take special tools to install.
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Post by JohnH on Oct 2, 2010 17:55:11 GMT -5
It does seem like a device for switching in different cap values, and it talks about having 16 positions. Standard rotary switches can have 12 positions, so one of those could be the basis of an inexpensive home made version.
Lets say 1st position is off - no cap. A guitar and 10' cord, with some self capacitance of the pups has a capacitance of about 600pF. So the object would be to add extra caps to give a series of equal-ratio increments up to the max value of 22nF
So with 12 positions, a series of extra caps to be switched in might be:
1 0 2 250pF 3 560pF 4 1nF 5 1.5nF 6 2.5nF 7 3.9nF 8 5.6nF 9 8.2nF 10 10nF 11 15nF 12 22nF
Each increment adds about 40 to 50% to the total, including 600pF self capacitance. At each step, the resonance and treble roll off will change by about 20 to 25%, or about 1/3 octave.
This would involve 11 capacitors all connected to ground at one end, selected by the switch. Another way, maybe easier to make, would be to have the caps in a series chain, the more caps in series selected, the smaller the value. For the same overall results, a suitable range would be:
1 0 2 470pF 3 1.2nF 4 2.5nF 5 4.7nF 6 8.2nF 7 12nF 8 18nF 9 25nF 10 33nF 11 47nF 12 22nF
So in pos 12, you get just the 22nF, and in pos 11, its 22nF in series with 47nF, which results in about 15nF etc, in position 10, a further 33nf is added to the chain, resulting in about 10nF etc
John
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