Author Topic: choke in pedals?  (Read 282 times)

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pinkjimiphoton

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choke in pedals?
« on: December 30, 2017, 04:58:50 PM »
dumb question...
but i needed a 100mh choke for a project, and it was cheaper to buy 100 of 'em than to buy ONE.
i only NEED one. so...
curious...

can you use them in power supply filtering in pedals as you would in say a tube amp?
like to find a use for 'em, figuring putting one in series with a filter cap and a diode or something to help smooth ripple can't be a BAD thing, right? or is it better to just stick with a small resistance, which in my limited understanding is for all intents doing the same thing a choke would do?

educate my dumb ass, please. and thank you!!
digi2t:
"Fuzz, distortion, and wah, are plenty abound. Mutron Flanger, not so much.  8)"
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iainpunk

Re: choke in pedals?
« Reply #1 on: December 30, 2017, 05:58:01 PM »
Hey.

Building a power supply with a choke could be more effective than a resistor in "cleaning up" a power supply.

The pros of using a choke/inductor is that it has a low DC resistance (compared to a resistor) but a higher reactance (resistance that only exists for AC, not DC)

The con is that the reactance is frequency dependant, and at 60Hz, the reactance ≈ 38ohm.

Of course using a second order filter (in this case a inductor in series and a capacitor to ground) the filtering effect could become much better than just an RC first order filter. Given that the right value capacitor is chosen. Id suggest trying a 100uf cap
If we don't study the mistakes of the future, we're bound to repeat them for the first time.
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Rob Strand

Re: choke in pedals?
« Reply #2 on: December 30, 2017, 06:14:01 PM »
Not all inductors are alike.  The problem with chokes is they have a maximum current and the DC resistance.

A low DC resistance and/or a high maximum current implies a larger choke.
That's why you see large 100mH iron core inductors on something like an amplifier power supply
and small 100mH ferrite core inductor on say an RF oscillator power supply.

Maximum current usually implies the core is saturating but it can also imply overheating and frying the winding.
If you saturate the core the inductance falls to a very small value so it might as well not be in circuit; basically it doesn't work.

It's always easier buy one, however, for small signal one-offs you can wind your own on a high mu ferrite tube core.  For inductors carrying significant DC you need to consider saturation - basically do proper design and it probably wont work on tube core unless it's low mu iron dust.

If you want to go full-on DIY you can use a stack of thin steel washers (better to dip each in lacquer first).   Often you end up with a fairly ill-defined/ill-behaved inductor which needs more turns than a ferrite tube.
The mind often distorts without gain.

iainpunk

Re: choke in pedals?
« Reply #3 on: December 30, 2017, 06:19:07 PM »
You can prevent saturation by haveing an air gap in the "magnetic circuit" . This does decrease the inductance, but increases the maximum voltage across the inductor.
If we don't study the mistakes of the future, we're bound to repeat them for the first time.
-Ken M

pinkjimiphoton

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Re: choke in pedals?
« Reply #4 on: December 31, 2017, 02:17:14 PM »
thanks brothers,
but i guess what my dumb ass is asking is is since i got 99 of 'em i don't need if i can just use 'em inline with the input voltage to help smooth any ripple.

it appears the answer is YES. maybe. depending on the application. these are all small things that look kinda like resistors, btw...
so figuring for my applications, mostly fuzzboxes usually, they should work fairly well in my usual simple power supply filtering...

i generally like two use 2 diodes, a small resistance and a big cap, so seems perhaps the small resistance can be changed to/augmented by one of these little inductors.

thanks gents!!!!
digi2t:
"Fuzz, distortion, and wah, are plenty abound. Mutron Flanger, not so much.  8)"
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Transmogrifox

Re: choke in pedals?
« Reply #5 on: December 31, 2017, 03:59:06 PM »
Adding some series resistance is a good idea because it will damp the resonance between the choke and filter caps.
trans·mog·ri·fy
tr.v. trans·mog·ri·fied, trans·mog·ri·fy·ing, trans·mog·ri·fies To change into a different shape or form, especially one that is fantastic or bizarre.

pinkjimiphoton

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Re: choke in pedals?
« Reply #6 on: December 31, 2017, 04:14:33 PM »
thanks transmogrifox, thats what my dumb ass needs is a straight answer. ;)

seems it will be worth trying on noisy ge fuzzes... thanks guys!
digi2t:
"Fuzz, distortion, and wah, are plenty abound. Mutron Flanger, not so much.  8)"
#FuzzyGoodness