Modify the Shure SM57 Microphone

In the new Tape Op you'll find this mod. Too long to type (I'm slow) but basically you completely remove the transformer. It's suppossed to sound very good. You lose 10db or so but gain low end. They talked about the option of making an external box with your choice of mic transformers of a better or different quality.

What do you think?

I may try it tonite.

Cliff Notes: Boil the body of the mic (only the section holding the transformer) for 5 minutes to loosen the gunk holding the transformer then pull it out & rewire without it. Thats it. You'll have to cut the wires first to separate the mic top/element from the body. DO NOT BOIL THAT.

Interesting.. Do you know if this would work with a SM58 as well?

They said it should/might - but the wiring is a little different.

Rode has a phantom powered preamp which can be fitted inside the mic, or you can do one yourself.

havn't recieved my tape op yet. so you take out the trafo and do what exactly? wire direct from the capsule to the XLR plug?

I can't pass judgement without reading the article but based on your description, it doesn't sound like a great idea. It sounds like a recipe for a lot of noise, with most mic preamps. Now, upgrading the transformer in the '57 wouldn't be a bad idea if you could find something good that fits.

[quote author="NewYorkDave"]I can't pass judgement without reading the article but based on your description, it doesn't sound like a great idea. It sounds like a recipe for a lot of noise, with most mic preamps. Now, upgrading the transformer in the '57 wouldn't be a bad idea if you could find something good that fits.[/quote]

I was thinking the same thing dave except for the part about trafo upgrade. I don't believe it could get better just different. 57's have that sound for better or worse,

There was a discussion of this over at Harvey Gerst's PSW forum a while back. I believe Jim Williams was the one who suggested removing the transformer.

You can read the thread here:

http://recforums.prosoundweb.com/index.php/t/8057/0/

Guess TapeOp was reading that thread as well.

Cheers,
--
Don

[quote author="khstudio"]
but basically you completely remove the transformer. It's suppossed to sound very good. You lose 10db or so but gain low end.[/quote]

SM57 = unidirectional dynamic mic. {if I am correct}

Unidirectional mics have two parts, pressure and velocity.
That velocity part is mass controlled, have proximity effect.
{low frequency end is enhanced if used in nonplane soudn field == close miking}
If you load microphone by transformer with small inductance, you see {via gyrator} capacitor in series, which performs like Hi - pass filter and
compensates proximity efect {and also reduces rumble} by 12 dB/oct!!!
If you remove transformer, you loose properties of dynamic cardioid mic.
Transformer itself "tunes capsule".

xvlk

Just re-read to make sure & that's what they're saying... Take out the transformer.

They say it sounds closer to an SM7. Also talked about using the RODE D-Power plug.


What would the impedence of the capsule be anyway?

well only one way to find out if it is good? right. Man I can't wait to read my tape op artical...
Here is a repost from another thread about modifiying the 57. Here is the How- to from Jim williams of audio upgrades... sounds like the same mod of which you speak

One way to do it is remove the capsule, (which by the way, doesn't "couple" to the body acoustically), unsolder the 2 wires and then remove the xlr connector. Throw the body into a pot of boiling water. After a few minutes, the hot glue will soften and then you can pull the transformer out. Now, take a look at that transformer. Ever seen such a pos? Be glad you tossed it away.

Now, wire up the 2 pins on the capsule to the xlr connector. I don't remember polarity, so you can check it against a stock 57 by putting the two mics together and matching gain. Pan to center and if they add, a-ok. If they cancel, reverse the wires for correct polarity.

Notice the large low end, somewhat like an SM-7. Notice the clearer top end, that's cause you removed that crap transformer.

Older Unydyne III's should be kept stock as they are rare and sound so much better than the Mexican 57's.

I noticed the sonic changes on these back in 1990. I called a shure engineer I knew for an explanation. He told me no changes were instituted, but original stampers and dies were sent down to Juarez. If you know about record pressing, stampers wear out and need to be changed regularly. As far as I know, old stampers and dies are still being used. This was the main source for the sonic changes in the mics.


--------------------------------------------------------------------------------
Jim Williams
Audio Upgrades

"jw" is full of "bs" on many things. you have been warned.

True he is. But was just reposting. Not to mention whats the harm in fooking up a SM 57 nothing other then out 100 bucks. Not really bad compared to fooking up a neumann :wink:

Maybe we could use the ARP (active ribbon preamp) to boost the level of SM58/57? Also Akg D-12 has a tiny xformer inside (seems to work fine without).

These threads could maybe put into microphone meta:

http://www.groupdiy.com/index.php?topic=5743&postdays=0&postorder=asc&highlight=ribbon+preamp&start=0

---
http://www.groupdiy.com/index.php?topic=6755#img_6571
http://www.groupdiy.com/index.php?topic=6775
http://diy.usedforcomparison.com/arp/

I did this with an early Shure 588 (same as 58).

I think the best modification for these mics is to fit them in a bin and replace them with B*eyer M201s because they generally sound crap.

You end up with something like 10 - 20 Ohms impedance at the mic.

The SM7 capsule is based around the original Unidyne III capsule. I have a Unidyne III. It is like a brighter SM57.

I remember that we have discuss this topic for a year ago, (around beginning of mars 2005.

I can not find the orginal topic, but I have save my posting:

I find a spare 545/R45 (SM57) capsule and a transformer on my workshop and done some measurment.
I measure a impedance (at 1 kHz) of 13 ohms and Shure say in a old paper for the R45 capsule, it shall be between 12 to 14 ohm.
The transformer have approx. +12 dB step up with 1kohm secondary load, and the frequency respons (between the -3 dB points) are 10 Hz to 50 kHz

--Bo

Yes, and a 12-14ohm source impedance is a pretty poor match for the input of a typical mic amp. (Hisssssssssss). It might work OK if your mic amp has an input xfmr with a "37 ohm" tap, but that's rare nowadays.

Shure wouldn't have gone through the trouble and expense of the transformer if it wasn't doing any good.

A little off topic but apparrently there's a lot of counterfeit shure 57's and 58's
around?

i recently bought a new 58 off evil bay. It looks the part, but sounds like crap.

anyone know a sure fire way to pick the fakes just by looking at em?

[quote author="Bo Hansén"]I remember that we have discuss this topic for a year ago, (around beginning of mars 2005.

I can not find the orginal topic,

[/quote]

Bo,

Making a search for SM57 with your name as an author gave me this:

http://www.groupdiy.com/index.php?topic=5977&highlight=sm57

:wink:

[quote author="Jeremy H"]A little off topic but apparrently there's a lot of counterfeit shure 57's and 58's
around?[/quote]

Not this one, right ?



No,oops, this is no '57, it's a '75...

http://www.thomann.de/thoiw7_the_tbone_mb75_prodinfo.html








Just a pity they gave it such a lame look & name - might be a good mic (for EU35 ?!) but why make it look like a Shure...