O.K. I've been trying alot of different parts out on both mics and have come to some conclusions. Here are some schematics that I've made up that show the mods that I've done to each mic. I have 2 for the 1050, one with the cathode follower and one without (which is how I have it at this time). The schematics also show voltages at different points for reference. The voltages change quite a bit depending on which resistors you use at different points. I'll update them as I finalize my mics, but I'm pretty much done at this point and plan to use them like this for awhile and see how they work.
This is as close to the C24 schematic as I could get, but with R6 and R10 with the C12 values and I left C1 and C2 in as they just filter AC from the circuit and are present in the C12VR. Removing R1 and changing R3&R4 to 499k's opened up the highs. Removing R5 made it a bit thin but removing C3 filled things back out. Think of C3 as a bypass to add highs back. So is C7, which I also removed because it's not present in the AKG's. Dropping R7 to 2.49k adds bottom extension and C6 controls how much you want to actually hear. The stock 100uf adds alot of bottom and also gain. The 2.49k adds the gain and fills out the mic without too much bottom, like the originals. C5 also acts like a bypass and by dropping to .oo47uf it opened up the "air" and clarity nicely. I'm really liking this mic as the open, clear yet full mic in my collection. I have the original zeners in the PSU, two 1N4761(75v).
I ultimately wound up removing the cathode follower because I have other mics that sounded about the same so I decided to try it without the CF and now it has a different character than my other mics. I must say that I'm not sure if this will be it's final configuration until I try it with some other voices to see if it fills a void in my collection. I actually tried a 3M and 2M at R3 and R4 respectively, which is the size used in the U47, but it dropped the voltage to around 45v at the capsule (before R10), so I stuck with the 499k's. I added R5 back as it thickened up the mic where before it was too close in sound to the Apex for me. I'm thinking about trying a 23ohm resistor at R7, which is what the U47 uses, just to see. The PSU originally had one 1N4764(100v) and one 1N4762(82v) zener, which was too high so I kept the 1N4764 and changed the other to a 1N4758(56v).
This actually sounded very good but, as I said above, I have other mics that sounded pretty much the same. I would probably put R5 back in if you're looking for a more U47ish response. You can also add a 1000pf cap where R2 connects to tube pin 1 and this softens the highs more if you want something even darker. Zeners are the same as the other 1050 schematic.
Overall observations are that;
R1&R2-control voltage to tube pin 1 and 3.
R3&R4-control voltage to the capsule.
R5,R10&R6-effect the sound of the capsule-smaller=darker, larger=add highs.
C4-effects the sound of the capsule also-larger=favor lows, smaller=add highs.
R7-effects the low freq extension-smaller=more bottom.
C6-effects low end depending on size-larger=more bottom. Also adds gain.
C7&C3-bypass to add highs.
C5-effects high end depending on size-larger=more bottom.
C8-effects low freq extension-Larger values=more bottom.
R8-smaller value adds bottom but loses gain.
R9-only part I haven't changed.
Hope this proves useful.
Lucio
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