OK, back home, and I just did the mods. DrBill has, with his drum samples post, set a new standard in shootouts that I will never attain. With that advance apology out of the way (and the disclaimer that I have no skills and don't know what I'm doing), I can say that I did take pictures and record short samples. I forgot to use the low tech match testing technique prior the mod, but I'll do it with the modded mics and post again.
OK first, here are the mics stock, with the victim capacitors indicated (my mics do not have the trim pot that Marik mentioned, unfortunately, but - not obvious in the picture, they do have 1G ohm resistors (those maroon plate-like looking things) unlike my 991):
and here's a stereo (using both mics at once) sample of a little drum thing and a porcelain bell that I've got. Unlike drBill, I'm going for information underload
http://recursor.net/mxl603/MXL-603-stock.wav
next, here they are with the input capacitors swapped:
the replacement 1000pf poly-something capacitors are a little bigger physically than the stock ceramic (also 1000pf) ones, but they fit fine. Here's the corresponding sample:
http://recursor.net/mxl603/MXL-603-inputcap.wav
sounds better to me -- one thing that may not be apparent in the sample is, despite my neaderthalic soldering skills and sub $10 soldering iron, the mics are less noisy.
next, I decided to follow Marik's advice and go with 1uf capacitors to replace the .22 ones -- I quickly realized that I had a form factor problem -- my first choice of replacements just didn't fit at all (actually, my first choice are these WIMA ones that would probably fit, but I only had one of them left !!! argh!!!). I managed to get these yellow ones in place by leaving long leads and tucking away -- being careful to avoid a short, of course:
here's the mic again, with the capacitors tucked away:
and here's the sample:
http://recursor.net/mxl603/MXL-603-.22to1uf.wav
[I did my best with mic placement across the samples, btw, using a stereo bar on a stand for the mics, and holding the drum and bell in as close to the same position as I could.]
even better, I think - more bass. And again, quieter. Thanks again, Marik! Next, I'll have to figure out how to remachine the capsules with my teeth
edit: matching is OK, but not fantastic, with the mismatch pronounced at lower frequencies - my guess is about 5-7 db off below 200hz. I'm speculating, but I imagine that by improving the bass response, I worsened the matching a little, since the poor bass response on the stock mics was masking the mismatch. I had the same effect with some MC-012s that I modified.
, and the few weeks is a worst case scenario kind of expectations-setting time frame ).