Modify the Shure SM57 Microphone

[CJ]

Well, that Geffell I took apart was M6, but that comes after a tube.

The mu metal also means less turns for the same inductance, so you get lower dcr, which you want so you can catch every microvolt possible out of the capsule. The less copper loss, the more signal. I bet the 57 capsule is a current device, not a voltage device, therfore, the dcr lets the current thru to magnetize the core, thus putting out a nice voltage on the sec.

Whats the 212?

 

[enthalpystudios]

i have a 57 that, after these metal vocal sessions last week or so, is pretty fucked up.

i've been noticing hum, regardless of cable, that happens when you jiggle the xlr on the mic, so i'm thinking theres a bad pin 2 or pin 3 connection inside.

anyway, going to check it, and try out an o-1.... any thoughts on that guy? much lower primary resistance, but is that the same as DCR?

figure a mic input trafo may just work pretty well for a mic output trafo.

well, got 4 of these and a couple o-9's to try out.... buck a piece!

i'll let you guys know how it goes.

billy

 

[enthalpystudios]

yeah, that ground "method" *is* really ghetto.

anyway, got the old one out, got wires in for the secondary (maybe backwards after all's said and done?) and the xlr connector.... which by the way, was lucky to still be connected to the trafo at all.

stuffed the o-1 in and lettin it sit, hopefully the residual hot glue will keep it in place when i finish some 'real' work.

anyway, i'll try soldering it up a little later.

wish i had a camera.... anyway, anyone (maybe cj?) know off hand where I should send the leads from the capsule? I have a green wire marked "2," and a yellow wire no marking. My first guess would be to put green to the + side of the primary.....

back later, hoefully i can get some samples done tonight.

wish i had of recorded something to compare to!

no patience

billy

 

[enthalpystudios]

well, got er in there.

sounds much much nicer, in my opinion, although I'm not sure I'm doing it the right way, as I'm all hack and no real knowledge ;]

anyway, i've got the capsule going to the O-1 50K secondary, and the primary at 500 ohms to the xlr.

seems to do what I assumed it would do, big stepdown (10:1, I suppose), requiring a lot of preamp gain. I think that's the source of my newfound noise floor...... it takes my green pre set to max gain to get a nice signal on a moderate singing voice.

Aside from the noise, it sounds real nice.

Wish the green wasn't my only pre to test out at the moment.

If this guy was hooked up the other way around, like 1:10 (500R->50K) and then sent into another O-1, backwards at 50K->500R, and then into a mic pre (through a small box or something), what would that do?

billy

 

[NewYorkDave]

You hooked it up backwards. You want the transformer to act as a step-up. You don't need to add a second transformer.

 

[enthalpystudios]

thanks dave, i had a feeling i had gone backwards....

could 1:10 be too large a step up? it's the smallest I can get with an O-1....

i also have some O-9's like cj used, but they look like they have a limited frequency response. (200-10k I think).

I was actually thinking of using O-1 in and O-9 out in your one-bottle until I realized the low bandwith of the O-9.

Although i think I remember reading PRR typing up something about the bandwith of an O-9 increasing when hooked up to a particular source or load.

Anyway, thanks for the heads up.

Going to go turn it around.... Really, the hardest part of using the ouncer is fitting it in the mic body.... I already removed the casing, and may slice out a groove for the wires that need to bend around to the 'bottom' of the ouncer.

but like I said, aside from the exceptional amount of hum I got from the cranked to max preamp, it sounded quite nice.

billy

 

[CJ]

The last transformer I stuck in the 57 checked out good on paper, but the mic did not like it much.
Not enough gain.
I think you really need a very low pri resistance for this mic.
1 or 2 ohms.

The stock 57 xfmr is probably as good as your gonna get, outside of bypassing it and putting it in front of a speaker cab.

But for low level stuff, you will not have the gain out of the mic that you need for a good s/n ratio, if you run the wrong xfmr or do the bypass.

 

[enthalpystudios]

well, back when dave enlightened me, I hooked it up the other way around, and that O-1 does actually sound pretty good in there.

a buddy of mine just got a couple new 57's, so I'll do an A/B one of these days.... imho, it sounds awesome

billy

 

[OneRoomStudio]

Any updates on this? I'm curious as to how other xformers sound in there. I just pulled the stock one out of mine, and will be doing some tests on it soon. As much as I like the stock 57, I could really use some more top end, but I hate to loose so much level. There may be no way to have both...but I can dream.

P.S. Big thanks again to CJ for all the research he did.

 

[enthalpystudios]

honestly, the O-1 might not be "right," as far as primary dcr goes, but i personally think it sounds pretty damn good in there. i was about to do an a/b a couple of times, but one time, i had a preamp 'situation' and it wasn't working out so well, and i finished a pair of api312's, and went to do it, and the leads between the capsule and the O-1 snapped again.... the wires off the capsule are very small....

anyway, i need to fix that puppy so its secure, and try and a/b on something, just to do it.

i like it a lot though, it will be useable for me, definitely different than stock.... like i said, i'll a/b it, i have a brand new one to test against\

billy

 

[OneRoomStudio]

When (and if) you get around to it, it would be very cool to hear some audio samples of a stock 57 against your version.

I stumbled across this transformer today:
Scroll down to CR45-704 under "General Purpose Audio Transformers"

http://www.kenselectronics.com/lists/audxmfr.html

Used in reverse it would be 3.2 : 500 with a center tap...that seems to be in the ball park of the original. I don't know if it would work properly (or if it would sound any better than the original). For $7.50 though, it might be worth a try.

Could someone confirm of deny if this would work?

 

[BYacey]

[quote author="OneRoomStudios"]Any updates on this? I'm curious as to how other xformers sound in there. I just pulled the stock one out of mine, and will be doing some tests on it soon. As much as I like the stock 57, I could really use some more top end, but I hate to loose so much level. There may be no way to have both...but I can dream.

P.S. Big thanks again to CJ for all the research he did.[/quote]
Run it stock into a high impedance balanced input, at least 50K, and you'll hear the top end. This reduces loading on the coil and makes the mic more sensitive to transient waves. This is what I found using the Valley pre on dynamic mics.

 

[CJ]

Good tip!

Remember that there are two major apps for the 57:

studio
stage

if you pull the transformer, you may not want to use it under the lights.

 

[Walrus]

[quote author="khstudio"]CJ,
Those pics show a regular 57.

I asked about an old Shure PE54D I have earlier... can anyone help with that? I wonder if it has a better transfomer... anybody?

Also, it has a switch so if it's not fixable, transplanting a good capsule in there & using the switch to bypass the trans (like mention earlier :thumb sound like a good idea. Plus I always liked the silver body :green:[/quote]
Arriving late as usual....
The PE54D was a standard Unidyne III 545SD mic, but supplied pre wired for high impedance, in a plastic carry case and with a XLR to jack cable.

 

[Walrus]

Hi CJ, just been reading about your disection of the 57. I used to do that for a living 25 odd years ago when I worked for the UK Shure importers. Except I had to fix them!! :wink:

The original 57/58 had a dual output transformer, 50 or 150 Ohms. This is probably why the old mic and new mic don't sound the same.
There was also a ground wire attached to the centre bolt of the cartridge which went to a copper spring plate holding the transformer in place, also "digging in" to the base sides to provide earhing of that. Then another wire from the plate down to pin one of the XLR.

 

[Walrus]

[quote author="rodabod"]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.[/quote]
Sorry, but the 588 Unisphere B was not the same as the SM58. The R8 cartrtridge was a 150 Ohm unit, and the mic was a 588SB for low impedance, then a transformer was fitted in the 588SA to make it high impedance.
Taking the transformer out of your one just gave you a standard 588SB.
Yes, the 588 was a vey cheap mic.

 

[Rossi]

Hi Walrus, you seem to know a lot about Shures! What about the Shure 565 SD Unisphere I - it can be wired either hi or lo impedanche. Is this the same cardridge as the SM58 with a dual output tranny or is it a 150 ohms cardridge like the 588?

 

[rodabod]

[quote author="Walrus"]
Sorry, but the 588 Unisphere B was not the same as the SM58.[/quote]

My apologies. I assumed they were the same.

However, I still stand by my argument that the cheaper Shures are pretty crap and that the Germans and Austrians do it better. :razz: But then you get what you pay for....

Walrus, any input on the SM7 and Unidyne 545 capsules?

Cheers,

Roddy

 

[CJ]

Good stuff, Walrus!

Hey, how do I get that pop screen back on the 57?

:twisted:

 

[Walrus]

[quote author="Rossi"]Hi Walrus, you seem to know a lot about Shures! What about the Shure 565 SD Unisphere I - it can be wired either hi or lo impedanche. Is this the same cardridge as the SM58 with a dual output tranny or is it a 150 ohms cardridge like the 588?[/quote]
The 565SD as you say, was hi/low wireable on the xlr base connector, but it used an R65 cartridge wheras the SM58 used an R59 cartridge.
Physically, the cartridges were very similar, the R65 had a metal cover to it's top plastic cover and the R59 had a foam top.

I once swapped the plastic tops over on the 2 cartridges and put them back on each others base/grille i.e 565 base/grille R59 cartridge with r65 plastic top and vice versa). To my limited hearing they still sounded like the 565 was a 565 and the 58 was a 58!