Hi Soundguy and everyone, Ive been saving all this up for a while, its a bit of a rant so here goes...
I bought a CMV563 with M7, M8 and M9 capsules last year from ebay and since then Joe and I have been trying several interesting mods with it.
When it first arrived it was non functional, but after replacing the electro caps in the mic as well as the tube (bought 2 EC92s and picked the quietest one, about 4db difference) it was up and going and sounding good.
Joe noticed that my mic had a more primative circuit to the 563 circuit thats floating around on the web. Hes drawn it out and hopefully will post it soon. It would be good to know which circuit each poster's CMV has, and to see if this correlates with the differing opinions of the mic's usefulness. Also, my PSU has no preamp in it. Just the usual bits and the reg tube.
Like I said, once my CMV was back to spec I thought it sounded good, with the M7. Ive found the M8 and M9 capsules to be unuseable because of their bizzare freq curve, which seems to be inherant in their design. They sound pretty much like the curves on the original data sheet, the M8 rolling off around 8k and the M9 with a massive rise around 8k and then a steep roll above 15k.
The M7 sounded fine though, fairly bright but with a delicate, sweet top end and a very pronounced proximity effect. It was amazing on accoustic guitars and great on fem vocals, and I also liked it as a drum overhead or room mic. It stands up to processing more than most of my other mics, you can eq, compress and distort it and it still tends to sit nicely in a mix.
Despite this, Joe and I were keen to see how it could be improved, or at least given more features.
The first mod we tried was removing the AC negative feedback from the tube. Joe devised an ingenius way to switch this in and out remotely. Ill let him give the details of this if he wants.
This mod increases the gain a few db, boosts the top end a little and seems to do something funny to the low mids, making them a little more thick and juicey. You could say it makes the mic sound a little more 'modern'. Its not a massive change but extremely useful, like having a similar mic to try if its not quite working, with the flick of a switch. Were using it on male vocals as I type this, with the mod in, and the singer and producer love the sound.
The other mod is to the M7 capsule. Upon opening it up we found that the back element was indeed fitted, just not connected to anything. Its solder tab is spaced so a magnetic reed switch fits perfectly between it and the tab for the front element. So we fitted the reed switch (again, Joe's idea) and now the capsule can be switched to omni by moving a magnet in front of the relay.
The only problem was holding the magnet there, as the surrounding metal is not magnetic. This was solved by soldering a small strip of steel onto one side of the switch so that it sat over the top and gave the magnet something to cling to. We also covered it in heatshrink so it cant short to the case.
The little rare earth magnet, about 8mm round, now sticks to the grill of the capsule when you want it in omni and is removed for cardioid. Omni sounds fantastic, very similar to cardioid but with no prox effect. We just used it very succesfully on a female singer who likes to get up close to the mic. Ive also tried it right up on the sound hole of an acc guitar, where I would usually never put a mic, and it sounds beautifully balanced and delicate.
Were looking at what can be done to the M8 and M9 capsules but its not looking promising. We might end up just using the cases and putting new capsules inside to get the right patterns.
Hopefully Ill post some photos and some sound examples up soon. Soundguy, Id love to hear what your CMVs sound like to compare it with mine.
Cheers,
Matt
