Please excuse my naivité, but I'm not sure how to work through a problem.
In recording my acoustic guitar, it seems that there is a ton of low end, or maybe I should properly say the high end is lacking, and I'm cutting out tons in the 100-250 range. On my male vocals I'm also cutting a lot of lows to get it to sound decent. Female vocals seem pretty smooth to my ears, and aren't a problem.
I'd like to know how to test my mic/pre/ chain to get a frequency plot so I can tell whether it's the pre, or the mic, or my imagination, or what.
I would then test the mics with a rented pre for comparison, and test my pre with other mics. I'm not thinking the converter is going to add this much colour.
Potentially relevant information:
-After much testing, I usually record an acoustic with a condenser about 10-12" out, pointed to where the body meets the neck. i'm careful to avoid the soundhole.
-I do male vocals about 10-12" from my condenser.
Mics: 2 KEL HM1 condensers, and 2-Audix OM2 dynamic.
Pre: an old Altec Lansing 1567, converted to 4 in, 4 out
Other-I go straight into a rack mount Delta 1010 and into the computer. My current 'studio' is an 11 X 16 room, with vaulted ceiling, and one wall which is not parallel, and all kinds of books and couches in there. When it's warm out I record on my deck outside(I live out in the sticks) so I don't think it's a room problem.
The problem sounds more like a microphone selection and placement problem. Using an LDC placed 10" from the 12th fret I also get a pretty bass heavy sound. If you think it's the pre, then try it with the pre in a cheep mixer to see if you still have the problem. If you want to get close and not boomy, try an omni on guitar. Vocals I always engage the low cut filter.
Just my .02
While I love those old mixers (I have 2) and I want a beautiful acoustic guitar sound? I use transistor condenser microphones & transistor preamps with better input transformers. Maybe you just warmed things up a little too much? Tubes with tubes & lousy transformers.
While you seem to have other good stuff. Have you ever just considered a pair of SM57's? Just because you use tubes & condensers in the same sentence doesn't mean you'll always get what you want. While I too have plenty of tube stuff. For the kind of presence I like, I'm usually using all transistors. While tubes deliver natural even order harmonic distortion, which sounds nice. It's the odd order harmonics that transistors deliver, which is dissonant but can add that extra harder harmonic presence. And that natural bandwidth limitations & presence rise in the venerable SM57 could do more for you than you realize. Leave the tube stuff for vocals.
Always practical. Practically always.
Ms. Remy Ann David