MXL 2001 circuit choices

This is mainly to Gus but I would appreciate anyone who could chime in. I've been researching the mods that can be done to this circuit, and I am on option overload.

Which set of mods created the most useful (workhorse) microphone to you? Also, I'd be interested in trying something unique or strange as long as it was musical and unique (lo-fi tone, abnormal frequency response, etc.). Do you have anything like that?

-James-

I just did the "U87 Front end mod." (Not sure who came up with that. but there is a schematic floating around. ) Stripped out the output stage and replaced the transformer.

It isn't in the mod, but I don't see why the capsule couldn't be directly connected. Also, I think there was a recent thread about adjusting the feed back network for different frequency.

The Aurycle mic is the same circuit and there is a thread here on that as well.

Well, I already built the DIY87, and I'm not sure the Chinese U-87ish would stack up next to it even with an upgraded transformer and electronics. Also, I intend to re-laminate the original 2:1 transformer to keep costs down.

Has anyone tried Gus' male rock vocal mods? Here is the thread:

http://www.groupdiy.com/index.php?topic=47569.0

If no one has tried it out, all I would need to attempt it myself is Gus' confirmation that these mods are a worthwhile upgrade, and the results are a useful recording tool. I assume that would be the end goal of any of Gus' designs, but I want to make sure time hasn't changed any opinions before I start buying parts. Thanks.

-James-

Really i dont think nothing sounds as good as Danny microphones.
I dont think theres any advantage on modding a 2001!

Build a fet or one more u87 with different transformers/capsule!

Just my humble opinion

I'm certain attempting to make a 2001 circuit sound like a Neumann is futile, but I can't resist putting more tools in my mic locker. I may have to be the guinea pig for Gus' design as it doesn't seem to fit in the "2001-to-U87 frontend mod" category...

As this actually the circuit from a Carvin CM-87S (Aurycle a460), it has low cut switch and -10dB pad. Would I still have access to the low cut function with the intended mods (due the changes around C6)? Thanks.

-James-

  Gus is not the type to just give out plain answers. His mod is pretty simple, and he's almost been begging someone to try it. Can't think of anyone better qualified...
  I've been waiting for a cheap donor with a decent capsule to come along. I think I have all the parts, but I kinda gave up on those capsules after playing with the RK-12s, and upgrading the caps in my MXL 2003.
  Give it a try.....let us know.

tchgtr said:

  Gus is not the type to just give out plain answers.

Click to expand...

I know Gus isn't the kind of guy that will spell it out for us, and I doubt he would have posted a circuit alteration if it were a waste of time. So I assume he liked the change enough to put it up here. I was just interested to see if that mod has served him well, or if his opinion has shifted.

-James-

HellfireStudios said:

As this actually the circuit from a Carvin CM-87S (Aurycle a460), it has low cut switch and -10dB pad.

Click to expand...

As an aside and FYI, I gutted a 2001 which as best I can tell, had the same pcb as the aurycle and I believe the same or very similar factory numbering.  It had a place for  the low cut switch, but the pads weren't used. The second 2001 I got did not have these pads and had a very slightly different PCB.

Do you happen to remember the differences to the circuit in your second 2001?

-James-

As best I can remember they were the same. The low cut pad just wasn't wired in to the circuit. I saved the board from the older one, I could dig it up, and I also have photos of the newer one on another site. I don't have ready access to some things because of some construction, but I could dig both out and look and see if the part values are all the same.

I did look into this a bit, because the PCB on the first one intrigued me with the unused pads, and when I was looking at the aurycles, it looked familiar. I also was trying to correlate the PCB numbering to an OEM, but could never cross reference it.

I appreciate the willingness to dig up that circuit, but there isn't much of a need (outside of general knowledge).
My only concern, before I try Gus' circuit, is whether I will be able to use the low cut switch with his changes? If so, will the cap (C7) value need changing seeing as C6 changes with Gus' mods? BTW, it is not the end of the world if the low cut switch must go. Just let me know so I can start my mouser order. Thanks.

-James-

The adjusted 2001 v67 etc circuit is a compromise.
As I posted before I bought a number of V67 microphones and wanted to test different adjustments to the circuit.  This is one of the adjusted circuits.
The posted adjustment has the MXLv67 part numbers

A little off topic.  The 32mm can sound OK.  The Honeybear microphone is an example(this is from an older thread I used a MXLV67 body built a fixed bias tube circuit and used the stock 32mm capsule) I also have two 2001s with tube circuits that don't sound bad with the stock 32mm.

So instead of building a tube circuit in a another V67 body I wanted to test what I could do using most of the stock parts of a V67 like circuit.  I wanted to keep the stock transformer and capsule and all the capsule mesh (I think removing the inner layer of the V67 capsule mesh is a mistake).

Keeping most of the stock parts I had a limitation of the capsule voltage so I wanted to work with that limitation.

I then thought what about an adjusted network for the EQ I used LT spice to adjust the RC coupling and network.

I did not like the stock biasing so I redid the biasing of both stages and gave the JFET stage more gain for the stock transformer. 

So having limited capsule voltage I though it might be fun to EQ for louder sources.

I adjusted one of my MXLV67s and tested it with headphones but have not brought elsewhere to test it properly.

If you like the sound with the reversible small amount of part changes you could then change the cap types, K67 like capsules JFET etc.

new parts needed
C1 .033uf
C8 .47uf
C6  .01uf NOTE you can move the .01uf from the stock C1 position to C6
ADDED a 1meg R100
R10 4.7k
R9 470k
R8 47k
R7  will need to be selected for biasing of the first stage,  Install new R8, 47K and the other resistors and measure the drain to ground voltage with the stock R7 value

This can be a good experiment to learn from (that's why I left most of the stock parts)and you might like the adjusted microphone.  It is not a lot of parts and it should be easy to do and can be removed and the microphone brought back to stock.
So before you tube the microphone or put another solid state circuit in people can try this.

Thanks for chiming in Gus. You can't beat info from the source. This sounds like a solid idea.

I plan on biasing with an oscilliscope to maximize headroom. I may change the FET to a low IDss 3819. I'm using a dual skinned 32mm capsule so I can try out both sides for the best sound. Also, it looks like I won't need the pad or the low cut, if this circuit is designed for louder/closer sources. That answers my question. Thanks.

-James-