johnc124 diyAudio Member

Join Date: Jan 2006 Location: Tucson, AZ

Quote: agdr Originally Posted by Didn't mean to imply there is any problem with the 47pF cap, given the explanation. That was a very well thought-out design and solution for Cload drive stability, from the blog article.



I think what I'm going to do for anti-thump protection is just add a small eletrolytic cap on each rail after the power switch to help force them to come up and go down at more-or-less the same time. Plus it should help de-bounce the power switch. Not low ESR, I want the audio currents to go back through the (presumed more linear) batteries or voltage regulator rather than an electrolytic. In fact I might add an ohm or two in series with the capacitors to make sure the electrolytics are not the primary signal current return path. Re-reading what I wrote above I should have said "the wider chip bandwidth is going to be OK for my project" because I have a separate input RF filter.Didn't mean to imply there is any problem with the 47pF cap, given the explanation. That was a very well thought-out design and solution for Cload drive stability, from the blog article.I think what I'm going to do for anti-thump protection is just add a small eletrolytic cap on each rail after the power switch to help force them to come up and go down at more-or-less the same time. Plus it should help de-bounce the power switch. Not low ESR, I want the audio currents to go back through the (presumed more linear) batteries or voltage regulator rather than an electrolytic. In fact I might add an ohm or two in series with the capacitors to make sure the electrolytics are not the primary signal current return path. I think you'll be surprised by the impedance of the batteries, especially 9V batteries. The ones I've measured in the lab showed about 3 ohms of series resistance, this directly turns into even-order harmonic distortion when the op amp delivers large currents to the load. So maybe no resistor in series with those caps on the supplies

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