Hi Wayne,
I haven't got past my very basic 1512 -> servo'd outpt (OP77) -> 1646 design. I had a hard drive crash this week which has cost me a lot of time, which is why I haven't been back to post.
I did get to run the basic preamps last Sunday recording some stereo electric guitar tracks, using a pair of Crowley and Tripp Naked Eye ribbon mics. My perception of the preamps in that application was that I didn't even notice them, which I think has to be a good thing & the whole point of this design. I was using 12-24 dB gain on the 1512 (so 18-30 dB overall).
I've just ordered up a pair of the 24 position goldpoint switches to give me better control.
Here are my latest calculations for the Rg, including the nearest 1% resistor values. I've tried to minimise the total error - hope it makes sense.
Thanks for the tip about using a pair of resistors to isolate stray capacitance - I'll give that a go on the next rebuild.
They may have been pointed out before but I found a couple of links to commercial DIY projects using THAT chips:
http://fivefishstudios.com/index.php?op ... &Itemid=59
http://www.seventhcircleaudio.com/T15/T ... _about.htm
Cheers!
Stewart