Eric Flynn sent me an email about some inexpensive mics which come with a 25mm capsule already installed.

Interesting that the capsule alone sells for $11 and the whole mic sells for $17.

Hi Eric,

Good find! I have seen a lot of these cheap mics advertised as having 25mm or 34mm capsules, but they actually had 16mm capsules when they arrived. Is the back side of the CM012 colored blue? I’ve heard from European mic builders of some 25mm “blue back” capsules which they like.

I forgot to add in the article that the wires to pins 2 & 3 of the XLR are usually swapped on Chinese mics compared with the standard phase of studio mics. Gotta do a small edit.

The TSB 2555B is unusual among inexpensive capsules in not having a peak at the top end. If you only have one or two mics, and every track you record has that peak, it builds up in the mix. The TSB capsules I’ve bought have been consistently good, however one which another builder sent me to test was not as flat — perhaps damaged in soldering?

I’ve pretty well filled my mic closet, but $16 is cheap enough to buy just out of curiosity.



Eric replies:

Right, I have bought several that advertised LDC's, and have an even worse 9/10mm electret.

No, the back is not blue. I have attached a pic of the back.   Yes, I have noticed the out of phase wiring as well.

So far, out of the 5 or 6 of the CM012's I am using, they seem consistent, but I have not done any real testing.

I have also attached an image of a PCB variant I have had on 2 mics now.  The top one is the variant, as the lower is obviously the typical board. As you can see, it came with a 9mm electret, disguised as a 16mm.

The variant has replaced the through hole FET, with an SMD part, as well as a significant number of additional passives, and different value electrolytics.  Its less noisy than the typical circuit , but they still come with the crummy capsule. Not bad when replaced with the CM012.

Henry sez:

If you have no objection, I’ll post your findings for other hobbyists. 

Interesting variant of the printed circuit since the more common PCB is laid out for SMT JFET, and the FET can be “Linkwitz’d”, depending how the board is stuffed. I hope the makers of those SMT aluminum caps have improved their seals. The ones from the 1990s and early 2000s are nearly all leaking by now.

I think I’ll order a mic and capsule to check out. I moved recently, and haven’t got my test bench set up yet. I’ll have to do that, check to see if results are consistent with what I measured before, so we have some idea about the objective responses of things tinkered with.

And Eric sez:

Yes, please do. No objections.

SMT aluminum electrolytics have improved a great deal. I am a EE in the automotive industry, and up to about 2010, we could not use them. We use them quite often now in non under hood applications.

Yes, the common PCD has the pads for the SMT FET, but I have yet to receive one that its populated.

I actually have one other variant as well. Its the typical board, with about half the components unpopulated.

Thanks, Eric! I found the mic also listed on eBay for a few dollars more. No luck so far finding more information on the CM012 capsules.