DIY M49/M50

[audiosweet]

http://www.groupdiy.com/index.php?topic=52563.0

A good friend of mine is basically reverse engineering the "Elvis mic".

[Jim Williams]

Now if he could only reverse engineer Elvis.

BTW, where do you get a real capsule for that mic?

[honkyjonk]

Theirsch M7 blue line?
Or do you mean if it's not Neumann or Geffell then why bother?

[Jim Williams]

To go through all that work, building, metal work, pcb's etc, and to not have an original or clone capsule makes me wonder why would someone go through all that hassle and expense. Appearance does not make the mic sound like the original.

Me, I did the same thing but used a $40 mic as the basis. It's the insides that count, unless you're shooting a video.

[Scodiddly]

The acoustic space inside the headbasket can have a dramatic effect on the sound of a microphone, though. It would be an interesting experiment to make some copies of classic headbaskets in such a way that you could easily plug a generic capsule into them for comparison.

[Gregg Juke]

There are so many "Elvis mike(s)" they almost rival the plethora of "Beatles mike(s)."

I want to reverse engineer the Tiny Tim mike or the Artie Schmeildtkin mike.

GJ

[Jim Williams]

There is a fellow that rebuilds Shure 555's. He puts a condenser capsule inside and adds colored leds.

Elvis would have liked it.

[dfuruta]

I want to reverse engineer the Tiny Tim mike

Goddamn I would buy that in a moment

[Marc Alan Goodman]

Looks pretty cool to me. M49 is one hell of a mic. I see what Jim's saying about their claming you can build a M50 with it. No way you can get a similarly spec'd spherical omni aluminum capsule, unless somebody over at Group DIY started building one, and even then I'd be pretty suspicious. Capsules are notoriously hard to build right.

As far as M49s go, I've heard Theirsh M7 blue line reskins and they're great capsules, and we've got one of his current production blue M7s in our Lucas CS-4 which sounds fantastic. So I'd say a M49 is totally reasonable. Yes you could do it in to a cheaper mic body but you lose two major things: the iconic look of the mic, and the particular acoustical properties of the head basket. Well worth it for $250 I'd think. Plus, people were doing it by hacking up TLM49s! This body is definitely a cheaper alternative than that. The hardest part would be sourcing a good AC701k, and anybody who tells you that's impossible is probably hoarding AC701s themselves. They're not cheap, but they're some of the most sturdy tubes I've ever come across.

[riggler]

Hi guys, I signed up so I could post about this.

Elvis used an M49 for a few sessions but I have also seen him on what look like 44's (77's too?) and U47's.

The 50 capsule is a tough beast, but not impossible. Backplate spacing is very close compared to lots of other omni capsules. Noise is more of an issue due to efficiency and so selecting a quiet tube is more important. In fact I suspect I might build the C version of the circuit first for lowest noise (cathode bias).

There were three versions of the M50 capsule, not necessarily corresponding to the 3 versions of the mic. I have what is very close to the latest version, KK83 capsules. Mine have an interference filter which I could carefully remove and be just about *there*. I have the spheres worked out.

Experimenting with headbasket shape, interesting results.

One layer of mesh, doesn't seem to make any difference (U47 shape versus 49 shape). But using the three layers like Neumann did now its more prominent. Does the dual angle slope break up standing waves? Probably. It sounds different. I don't have plots on that. My inner mesh in my tests wasn't the exact spec, but once I added that mesh layer there was a difference in sound to the ear.

I think you could do a bunch of different circuits for the headamp and they might all sound good! Given a good capsule and quiet tube... I don't have a real M49 or a 50 but I'd gamble that the output transformer has a lot to do with the sound but I may be wrong. I bet plate resistor / capacitor selection will change it too...

Well I did start looking at making 50 capsules. There is so much to learn, but I have a couple of cool people that have taught me some things, enough to know right now I can't make them!! (Even with access to a high precision machining facility.) I am not making these for business, so the guy that is handling the machining and myself are only running 50. We just wanted to make the bodies happen.

Damian