Gus' MXL 603s mod - Pictures/Part numbers -thanks Flatpicker

[rantanplan]

Hi abechap024

Thanks for your reply!

Mine sound good, too... much more bottom than before. But the rumbling made them almost unusable. Hope this disappears when they're "dry" again.

Cheers

 

[rmandelbaum]

I know this is an old thread but  will try anyway.

I have a pair of MXL 604s I an going to mod, my first mod  by the way. I ordered the caps from Mouser. I have some questions I hope I can get answered here.

1. How the heck do you get past the switch to get them open?

      OK, so I figured that out, the switch you see is a cap that comes off as you slide the guts out of the tube.

2. I have read that changing the FET helps a lot, where is it on the board and what do I change it to?
3. capsule change, should I buy a pair already modded or can I do this myself?

Thank you in advance

 

[rantanplan]

Hi there

I replaced C3 and C4 in one of my 991s with Panasonic ECQV .47uF, in the other with WIMA MKS2 .47uF.

I didn't do much testing so far, but one thing is evident: The WIMA one has a higher signal level of approx. +6dB!

The Panasonic ones have almost the same level as the unmodified one.

I also swapped the capsules: No change.

Is this possible only because of the caps' type?

 

[777funk]

Would replacing the .2uF's with .1uF's cut the bass response a hair? I don't have a schematic on this mic. I did that tonight and it did seem to help. I was getting boomy lows on an acoustic.

 

[damien]

Hi everybody,
I have a pair of T-Bone SC-100 II which are the Alctron T-02A. (they have the lo-cut and -10dB pad switches).
I use them for a very very long time (2002) and like them for acoustic guitar. They lack a little bit of mids to my taste.
Do you know if I upgrade mine with those WIMA caps according to the GUS mod it's going to work as well?
Here is some pictures of the PCBs CM-90W.

Thanks

 

[damien]

Just for information, I replaced all the caps to WIMA, electrolytics by Panasonic, and the capsule capacitor to Xicon polystyrene 1000uF on a pair of TBone SC100-II.
I also replaced the N-JFET for a LSK170B-TO-92-3L-BK by Linear Integrated Systems.
The difference before/after just resides in the top end being a tad smoother and the noise level a bit better than the stock version. Better noise floor is probably because I cleaned up the PCB and redone solders, use thicker wires and the new LSK170B.
BUT
I also got a pair of newer Alctron T02-A which are basically the same based on the Schoeps CMC circuit and they improved the quality of components overtime and the difference between a new Alctron and my modded SC100-II is negligible.

NOTE: Polystyrene capacitor are very sensitive and even if some were testing right at 1000uF, when I put them on the board, the microphone was not working properly and had almost no gain. I spent a long time finding what was wrong but one of the styrene capacitor I replaced was bad. I only found the culprit by swapping components between PCBs that lead me to the Xicon Polystyrene being damaged.

TLDR: You want a nice little pair of small condenser microphone? Buy a pair of Alctron or T-Bone SC-140 you can't go wrong. I don't think spending time and money on modding the old versions is worth it.

 

[Flatpicker]

Blast from the past. I did this a lot back in the day. I got the most mileage from just changing the cap between the capsule and FET to a polystyrene. One of my favorite mics is a CAD GXL 2200 that I simply swapped the capsule for a RK47 and this cap to polystyrene.

 

[damien]

Blast from the past. I did this a lot back in the day. I got the most mileage from just changing the cap between the capsule and FET to a polystyrene. One of my favorite mics is a CAD GXL 2200 that I simply swapped the capsule for a RK47 and this cap to polystyrene.

Replacing the capsule will definitely be the most dramatic change. I remember doing a test at every stage of the process, and from a component stand point, changing the N-JFET K170 and the polystyrene cap are the most important. To help future mod enthusiasts, just go for the Xicon Polystyrene capacitor 1000uF (23P210) and this is the best you can do for the price (0.30$).

I was also thinking about putting 1% resistors matched for the same bias, it could help if working with 2 microphones in pair. (R9,R14 for SC110-II, MXL603s have a trim pot R5, R6)

 

[damien]

As a reminder, here is the diagram of the MXL603s: