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Posts by tangent

 This is true.  However, it does seem to be a legitimate mystery, rather than something like some meaningless process variation.  I recommend that you pursue it only if you would be gratified to know the answer.  If you don't care why it's happening, don't waste your time. :) Rotating the buffers was a good test.  I should have thought of that myself. You've already rotated the op-amps, which means you're now down to the passives.  That's only likely to find problems in...
 The only reason we expect the ground channel's DC offset to be lower is that it's always unity gain, whereas the other channels can be higher, which magnifies any inherent DC offsets. Given that all three of your amp channels are G=1, I'd expect them to all be well under 20 mV.  If you're changing OPAG and nothing changes, then the problem almost certainly isn't the op-amp, since there are manufacturing variations in op-amps that ensure variable DC offset. I would measure...
 It's especially easy in this case, since solid tantalums typically have their positive lead marked, while alum elecs have their negative lead marked. I've also heard that some LEDs are marked "backwards" compared to the standard way. Bottom line, always check the data sheet.
We have so many different capacitor types because they each have their advantages and disadvantages. Typically the only thing that can replace a tantalum is an aluminum electrolytic, which is much more susceptible to heat, a serious consideration for that particular cap, being right next to a voltage regulator.   Cap types that aren't still useful typically get dropped from the manufacturers' lines. Tants are still being made despite the difficulty of getting the...
 I would be happier with that procedure if you had a known-good instance in the group for comparison. As you say, it is possible that you could get them all backwards.  I doubt it. I would guess that the regulator isn't regulating for some reason, so that the full rectified DC voltage is getting through, and that voltage is too much for the cap. If that's an LM317 you've got bent partly out of the frame, I would cut the remains of C8 off the board then power it back up...
The cap almost certainly popped because you put it in backwards. The instructions in the LNMP assembly guide told you to be sure to get the polarity right, but you either missed that, or you didn't understand the significance of what it was telling you, or you didn't look up the meaning of the markings on the cap you chose.   If you're trying to learn to swim by jumping straight into the deep end of the pool, you're going about it the right way.   If you're just trying...
 Yes. I'm still uncertain whether you finished building and testing the LNMP, and whether it works correctly.
Sounds plausible.
 Well, there's actually an interesting point. Many circuits that run just fine with either a negligible load or a purely resistive load get downright cranky when you drop a few hundred pF on its output. Many audio cable designs are actually surprisingly high in capacitance, given that they would be considered poor capacitor designs if that's what you were trying to accomplish. Some of these crazy designs you see...I wonder how many of them have even higher capacitance than...
The 22 kΩ resistor inline with the 20 kΩ pot is a passive attenuator.
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