Originally Posted by nutt7
I mainly want li ion due to its punch per size benefit.
Nothing comes for free.
If we had fusion batteries, we'd have DIYers jumping up and down to use them, and isn't that cool yellow and black triangle logo on the side awesome?
find myself wanting more voltage and current for some super low impedance headphones.
Have you read my Op Amp Working Voltage Considerations article?
As for voltage, here's a short exercise from the article:
18V runs down to about 14V in alkaline. Subtract 6V for a non-RRIO op-amp, and another 1V for virtual ground shift, which leaves 7V. Dividing that by 2.828 gives ~2.5Vrms into your cans. Even if they're really, really inefficient, that's still plenty of volume.
As for current, there are lithium rechargeables in 9V packaging.
This solves the danger a couple of ways. First, someone else designed the battery, presumably correctly. Second, there also exist 9V lithium chargers, so you get that professionally designed for you. Third, battery charging happens outside the amp enclosure, so you can do it somewhere safer than on your desk, or wherever.
That said, a stock CMoy isn't going to put out a lot of current, no matter how studly your battery. You need a strong output stage if you are going to make much use of a low ESR battery.
("Low ESR" is a more accurate way of saying "high output current ability". A 9V alkaline can put out over 1A for a short time. The reason we describe 9V alkalines as not being good for high current is the ~3Ω ESR, which means at 100 mA, they're dropping 0.3V.)
If you also choose a more stable virtual ground, you may find that 1x9V is plenty. Again, see the "working voltage" article, and check your headphones' sensitivity spec. I think you'll find that 1 or 1.2 Vrms into the cans is sufficient to raise your audiologist's eyebrows.
Edited by tangent - 2/18/14 at 10:55am