why use output caps when you can use an inductor? - diyAudio
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Old 6th February 2008, 07:27 PM   #1
cuibono is offline cuibono  United States
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Default why use output caps when you can use an inductor?

Can't you make a high pass filter with an inductor to ground? Wouldn't that make it possible to not use capacitors in the signal path?

I'll guess there are some practical restraints - are inductors more expensive? Less linear?

Hmmm...

I'm not real sure of how to calculate the inductor needed, because there is no resistor to ground, and I don't know how this would affect the in/out impedance. But assuming a 200ohm series resistor, you would need a 53mH inductor to ground. Not too bad right?

Why don't we see inductors used in stage coupling?
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Old 6th February 2008, 07:43 PM   #2
dhaen is offline dhaen  Europe
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Quote:
Can't you make a high pass filter with an inductor to ground?
Yes

Quote:
Wouldn't that make it possible to not use capacitors in the signal path?
Only if there was no DC on the signal.

Of course there are people who hate (costly) inductors and use every trick to avoid them, including buying ruinously expensive caps....


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Why don't we see inductors used in stage coupling?
Well they are used in some valve (tube) circuits, directly where the DC level is correct, or in combination with a cap when it isn't.
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Old 6th February 2008, 10:48 PM   #3
cuibono is offline cuibono  United States
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Quote:
Originally posted by dhaen


Only if there was no DC on the signal.
Sorry, I was assuming there was some offending DC offset one was trying to block: I figured that an inductive shunt would work just as well for eliminating DC by creating a short between it and the ground. Maybe there would be too much current drawn...

Let me rephrase: why don't you see inductors used to shunt DC out of the signal path, rather than using a capacitor to block it?
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Old 6th February 2008, 10:56 PM   #4
Jeb-D. is offline Jeb-D.  United States
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I don't think your amplifier will appreciate being shorted to ground in the lower frequencies
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Old 6th February 2008, 10:56 PM   #5
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Blocking = little current draw
Shunting = large current draw.
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