The buffer design posted here previously used a 1uF output capacitor. This could cause problems with feeding devices with low (like <10k) input impedance, which isn't ideal given that the whole point of a buffer stage is to be able to drive low impedances. I would rather have something closer to 10uF, but they get quite large. The easy solution is to simply locate the capacitor off of the circuit board. This gives maximum flexibility for choice of capacitors.
Another goal of this design was to have a building block that could be used for other circuits, particulalry crossovers. An active crossover is basically a bunch of buffers with various RC filters in between. By also leaving off the input capacitor, we gain the flexibility to use this in configurations needed to implement crossovers and other RC filters. I plan to publish nice writeups on applications for this, so using the buffer to build common components will not require a full design. I would also like to offer a version that is a traditional gain stage as well, which could be used to build a moving-coil phono pre-preamp.
Please post a comment to let me know what you all think of this strategy. Is the additional versatility worth the slightly more advanced construction techniques needed to mount a couple capacitors and resistors off of the main board?
Posted by jsn