Modify the Shure SM57 Microphone

[CJ]

This 57 went down to 10 hz, you could feel the capsule a thumpin.
I do not think you will damage that heavy foil if you keep the volume down.

Someone ought to diy a 57 with a tweeter or something.
And use a NS 10 tweeter. Since no one will care! :grin:

 

[ciminosound]

Straight from the horses mouth!

SM57 Sm7 Shure answer base Not Identical, but similar.

And more SM57 lore Shure Site

 

[CJ]

Perfect!
Thanks Gerry!

I had a chance to dis assemble that 57 xfmr, there is some Son of Flubber glue in there that loosens up real nice with a little heat:

http://vacuumbrain.com/The_Lab/TA/Microphone/SM57/57_1.jpg

If you are having problems getting the XLR out, this might help.
That screw gets Un screwed to secure the jack. So that means to remove the jack, you screw it in depper, not loosen it. When you uncsrew it, it rises into a keeper hole in the body.
Check the cheap-azz ground method used here:

http://vacuumbrain.com/The_Lab/TA/Microphone/SM57/57_3.jpg

With the xlr wires cut, the xfmr can come out the top.
Here comes the flubber:

There's all my leakage! Right where I expected it.
See the red outer secondary?
See how far it is from the core?
Bad news. No coupling. Thats where the 4 mH leakage comes from.
The pri (red inner winding) leakage is not that bad because the winding is closer to the core.
This is noplace for a bobbin wound transformer.This application really needs a layerd paper approach. This gets the wires right on the core.
A very delicate signal (unless miking Def Tones Ampeg cabs)
needs an efficient transformer. This is the first transformer that had a varying tuns ratio based on level, so I knew it was going to be a piece.
Voltage ratio went up with level due to low linkage factors.

 

[soundguy]

more proof that there is science behind everything.

dave

 

[CJ]

Thats what I was thinkin.
It's finding the science that's the hard part.

Coil without the lams. Kind of a thin disk approach.
Pri - Sec as expected.
Lams were weird. Just the E pieces. Never seen that.
But maybe thats why you can hammer these guys so hard and they still sound good. Lam structure keeps core from saturating. With just the E's, it's kind of between a gapped and non gapped xfmr.
Lundahl 7903 and Marinair Input use same idea.

http://vacuumbrain.com/The_Lab/TA/Microphone/SM57/57_10.jpg

Time to count the turns. Oh, fun. :evil:

 

[CJ]

Sec.:

561 turns of dot 06 - 35 ga. red enamel. Back and forth winding, no insulation of any kind.

Pri. : 121 turns of dot 01 (30-31 ga) green enamel

Real turns ratio:

1:4.63

sec gets wound rite on top- no big-no voltage.

Bobbin is 1/4 high anf 3/4 square with lead slots.

http://vacuumbrain.com/The_Lab/TA/Microphone/SM57/57_bobbin.jpg

OK. I have to put this together before I go to the hole.

So now what?

Well, I would say

1. This is not the best transformer I have ever seen.
But, maybe this is a perfect match for the 57 capsule.

2. Or, would up grading the xfmr to something hi-fi make a huge difference?

To find out, I would get a Triad moving coil, or similar 75:600 type xfmr. Remove it from it's can, and splice it in. That would be an easy mod that I will try.

later gator.

cj

 

[NewYorkDave]

Others talk, CJ does. He is Action Man.

 

[khstudio]

Your not kidding.

 

[soundguy]

the cj action figure definitley has the kung fu grip.

dave

 

[AnalogPackrat]

And Turkey Elbow :razz:

Accessorize your CJ Joe action figure with a butane torch, hacksaw, and heatgun! Butane not included. Soon to be released: CJ Joe's secret lab with Bridgeport Mill, mu-metal can opener, electronic test bench, and life like test equipment. Clutter not included.

 

[Gus]

How long before someone writes something in tapeop about how the transformer expands the sound(because of the cheap winding of sec over pri) with signal level from CJs work.

 

[CJ]

Hah! Thats a good one!

I was wondering if they expand the sec to make it "earthy" against the mic case, capacitance, etc.

I flashed on the fact that there is one mod that will improve the 57.
But it has nothing to do with the sound!
Or maybe it will.

Noise. I think a humbucking xfmr in that mic would reduce noise. Might even be able to lay the sucker on a SCR dimmer lamp operating at 10 percent.
MAybe not, bnut worth a try.

As luck would have it, someone sent a UTC 0-9.

Perfect for the 57 except dcr is 24 instaed of a couple of ohms on pri. Still want to try it.

Cherck this action:

 

[Marik]

Hey CJ,

Our local surplus had quite a few ouncers (at least that was when I checked last year). Let me know if you need any, I can go check.

 

[43hertz]

Here's a question and a thought, feel free to ridicule me if this is basic.

Question:

How does the distance from the mic capsule to the transformer
affect the sound/level/operation of the mic? Does it make a difference if the transformer is an inch away versus a foot away, for example?

Thought:

If it makes no, or very little difference, couldn't you take the transformer out of the mic and mount it into a small metal box with XLR
i/o's, and have a modded or non-modded 57 merely by inserting or removing the transformer enclosure? If there is a transformer that is the
golden wooly bomb on a particular source but won't fit in the mic, couldn't this be the workaround? I envision a box with multiple transformers, either switched or manually selectable by plugging into the correct ports,
that could give you a wide-ranging pallette(sp?) of sounds from one type of readily available mic?

Return fire now.

Gary

 

[fucanay]

[quote author="43hertz"]
If it makes no, or very little difference, couldn't you take the transformer out of the mic and mount it into a small metal box with XLR
i/o's, and have a modded or non-modded 57 merely by inserting or removing the transformer enclosure? If there is a transformer that is the
golden wooly bomb on a particular source but won't fit in the mic, couldn't this be the workaround? I envision a box with multiple transformers, either switched or manually selectable by plugging into the correct ports,
that could give you a wide-ranging pallette(sp?) of sounds from one type of readily available mic?

Return fire now.

Gary[/quote]

I'm no expert either, but I think that could work if you could find correctly speced transformers. I mean, the mic works without the transformer so it should work this way too. You could probably even put a few different transformers in one box and make them switchable to achieve different sounds. But I assume this also requires find transformers that actually work with the 57.

Matt

 

[CJ]

This ouncer has taps so maybe an impedance sw would be possible.

This mic is designed to operate on a wide swing of sound levels.
I guess that crappy xfmr will take a lot of level.

I could see having a 57 with a transformer best for vocals, and maybe a few more with different transformers designed for differt things, like guitar and bass micing, dri=ums, etc.

Use a sensitive xfmr for vocals and a heavy duty xfmr for other things.

If you use a xfmr with a higher turns ratio, you should get better sensitivity.

 

[43hertz]

Any thoughts about the distance issue from anyone? Will it matter?
For instance, can I rackmount it next to my mic patchfield or would I be better off making an in-line box that would be a foot or two behind the mic
on the floor of the drum/guitar/weasel booth?

 

[Herm]

I am confused here. I removed my transformer and when record any thing with my moded 57 there is less low end than the 57 that is not modified.
I thought well maybe I had my leads turned around the wrong way but when I changed them it still sounded the same way and was out of phase with the other 57. They would cancel each other out.
So Any suggestions as to what I might have done wrong here?
My mics are the Mexican models.

 

[Gus]

you might not have done anything wrong.

What preamp was used? you would need to turn up the gain to match levels.

Maybe this is what does happen.

I believe what you read on the web needs to be tested.
You have tested it and reported what you found. interesting

I only have one 57 so I have not done this test yet

 

[pucho812]

[quote author="pucho812"]did some inital testing last night recording drums. On top snare we had a stock 57 and next to it a trafoless 57. Did some A/B testing and the conclusion was

1. Trafo less had lower volume and had to crank the mic pre more to volume match however this didn't add any noticable noise

2.the trafoless one sounded tighter and didn't pick up the snare ringing as much as the stock one

3. THe trafoless one sounded "phatter" then the stock one

4. Trafoless one was not as midrangy as the stock one

Yeah a good mod but not an end all be all expecially since a stock 57 sounds good on certain things.[/quote]

o.k. we did the tests on a trident 80C. Had to play with gain levels to do matching. and the results above where our findings.