People are always saying that the Altec 1588B modules are noisy, thats BS. If you recap them there are no noise issues, its a very clean pre amp under normal gain settings, but gets wonderfully hairy when you drive it. I find it to be an incredible pre on rock drums, I can color each to taste. Anyway, the mod to give the 1588B module enough gain to stand alone and have a direct output pulled from all these altec mixers (1592a and B, 1599A and B, modular 1581A, etc) is fairly simple, plus while you have the shell off the module you can go ahead and swap out the electrolytic caps. Here are the pics describing the mod.

For the direct output mod the first picture shows you whats going on there. Note that the resistors are changed and  the 1 MEG output pot is changed to a 1 K pot. You can tap the output of the pot directly and add a buffer stage or an output transformer to taste.