[Quoting kvant]> Op-amps. I came into possession of a few OPA2132PA's and a few OPA2277P's
The OPA2132 is FET-input, whereas OPA2277 looks like bipolar input. That means the later one needs larger input bias current, which could cause too large voltage offset at the output of your amplifier.
So basically, don't use it. Got it. 
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> Power supply. I'll probably end up using batteries, simply because of all the horror stories ... about wall-supplied sources
9V should be OK. However, I don't think wall power is that dangerous. I have one off-the-shelf switch-mode wallwart, one off-the-shelf regulated linear wallwart and one simple "capacitance multiplier" filtered power supply I built myself. All of these work just fine for my audio needs. I am sure they do not provide the highest fidelity possible, but simple cmoy amp is not likely to be in that category either.
I guess I could use batteries for now, maybe modify later for wall power/combination.
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> ...which virtual ground circuit to use. I was looking at this page, particularly at the TLE2426 design.
Yes, TLE2426 alone might not be optimal solution for Grado load. A resistor divider followed with a bigger buffer than TLE2426 contains would probably be better option. These are discussed in that Tangent's article too. You might also want to check this thread, post #24 in particular.
Wow, some of the topics in that thread are a little, um, advanced for me
Anyway, (checks some numbers), the amount of mA to drive my 32ohm headphones at .5v (arbitrary value derived from tangent's op-amp page) is... 15.6mA - which is pretty close for the TLE, especially since that doesn't account for other components. So maybe I should consider the BUF634 method? the op-amp method? Could I use the extra OPA2277's for that? The OPA2132's? Anything else?
Thanks so much!
poly-p man
posted 02-20-2008 06:49 PM CST (US) 
