Hey guys, I've got a couple more questions when it comes to caps. I've been reading Art of Electronics lately and I am starting to get a grip on solid state electronics; tube stuff is still beyond me. Why are the CA2/CA9 caps "in the signal pathway", and therefore important to use "nice sounding" ones there? It looks to me like they just go to ground....? Do they provide a pathway to ground for any DC voltage from the input, like a low pass filter?
As far as settling on caps goes, I am sticking with BG NX 680uF caps for the CA7 positions, and Auricap .47uF caps for the CA8 positions. If I am calculating correctly that gives me a -3dB point of 4.4 Hz, for the resistance that the two caps in parallel see (RB14 + RA4 in parallel with 32ohm grado cans). If I increase the RB14 resistor to, say, 40 ohms I can drop that down to a -3dB point of 3.3 Hz. In the first case I'd think you would get a flat frequency response from about 40Hz and up; for the second I'd expect one from about 30 Hz and up. For those of you who have worked with the prototype amps, any idea how well the trade-off value is for doing something like that? I understand that you would lose some gain, but a I have read that losing some of the gain would be a pretty good idea for grados anyway.
If I am right about CA2/CA9 positions being a low pass filter, I thought that for amps where the inputs and outputs are both capacitively coupled you needed to increase the capacitance at both the output and input in order to get the -3dB point at the frequency where you want it? Wouldn't that call for even larger caps at the CA7/CA8 position as well? Or would "overcompensating" at the CA2 position with the 1000uF caps remedy the situation and allow for the typical values at the CA7/CA8 positions.
One last thing, I've yet to see the symbols on the schematic labeled "TA2L1" and the like. They look kind of like paint brushes or fountain pins. What do they mean?
