# Phantom Power through a Shure SM57



## blademaster (Apr 5, 2007)

While i was writing some stuff down on a sheet my hand accidentally hit the phantom power button for a channel and connected to that channel was a Shure SM57. after that happened the mic seemed to hardly produce high volumes of sound. i switched mics to a peavey p51 and it was back to norm. how was this caused? and how can i fix the shure?


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## audioslavematt (Apr 5, 2007)

Phantom power should not hurt an SM57. Are you sure you didn't actually engage the pad?


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## Eboy87 (Apr 5, 2007)

The way phantom works, the mic wouldn't exactly "see" the phantom power. There'd still be voltage delivered to the mic, but it would cancel out. What board were you using? Like Matt said, perhaps you engaged the pad, or something else. There's a million reasons why you'd lose signal on a mic. Perhaps it may even be a bad XLR connection, or a problem with the board itself like a loose ribbon cable.


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## BenFranske (Apr 6, 2007)

There are a lot of less expensive boards (Mackie and Behringer come to mind) where the entire board is phantom on or off and others where groups of channels are phantom on or off. In these cases you are often sending phantom power to dynamic mics so it's unlikely that your bumping the phantom switch damaged the mic.


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## blademaster (Apr 6, 2007)

i still was getting a signal on it. but it was very faint. i switched mics to a peavey and it worked just fine. i am using a allen and heath gl2200 40ch sound board. i know for a fact that it wasnt the pad button because that was the first thing i checked after i noticed the issue.

how would the phantom cancel out?


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## blademaster (Apr 6, 2007)

each individual channel has its own phantom power switch. and since this is a cardoid shure sm57 and not a dynamic mic like say the sm81.


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## blademaster (Apr 6, 2007)

hey mat for the sake of CB why dont you put in your ideas that we talked about in here as well


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## soundlight (Apr 6, 2007)

blademaster said:


> since this is a cardoid shure sm57 and not a dynamic mic like say the sm81.


No offense, but I'd read up on microphone terminology if I were you! A SM57 is dynamic and cardioid, dynamic refers to the element type and cardioid refers to the pickup pattern. A condenser mic requires phantom power. The SM81 is _not_ dynamic, but rather condenser, but still has a cardioid polar pattern.


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## audioslavematt (Apr 6, 2007)

I suppose, but the more I think about it, the more I think it's wrong.

There's a common modification that a lot of studio guys like to make to SM57s that involves removing the transformer. I've never tried the modification, but supposedly the low end is better. Transformers do not pass DC, so my theory was the previous owner modded it. I looked into it more and found this. http://www.churchmedia.net/CMN/audio/17017-shure-sm57-modification-experiment-described.html


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## blademaster (Apr 6, 2007)

i am sorry soundlight. my bad i have read up on it though not a lot recently, as well as dealing with various other stuff in my life has stressed me out. sorry. what i meant and thought of was condenser though the words didnt come out right.


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## stantonsound (Apr 6, 2007)

Unless something very bad has happened to the 57, it should not be doing this. If the element or the wiring leading to it was in some way compromised, like something grounding out, I guess that this could happen. I would imagine that the sound with the phantom turned off it would still be pretty bad if this were the case.

A 57 should not be doing this. I would suggest putting the mic in a box with $55 and send it back to Shure. 

http://www.shure.com/ProAudio/ServiceAndWarranty/ServicePolicies/index.htm


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## avkid (Apr 6, 2007)

stantonsound said:


> A 57 should not be doing this. I would suggest putting the mic in a box with $55 and send it back to Shure.
> http://www.shure.com/ProAudio/ServiceAndWarranty/ServicePolicies/index.htm


Their turnaround averages about 2 weeks lately. 
That's crazy fast when you consider the rate at which FedEx or UPS ships.


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## Eboy87 (Apr 6, 2007)

I was just going to suggest that Stantonsound. I suppose that it is possible that the element did short to ground, sending the full 48v through the mic. Another theory, did you hit the phase switch by accident? Did you adjust the gain pot at all after trying the PV mic?


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## SHARYNF (Apr 6, 2007)

*Re: Phantom Power through a Shure BUT*

The Mod to remove the transformer did reduce the output level by about 10db.
The transformer is not what protects the mic capsule from phantom power, it is how the phantom power is wired up, SO if you have a mis wired mic cable then you could possibly have cooked the capsule. Phantom power puts the PLUS 48 volts on BOTH pin 2 and 3 and the Negative is on Pin 1. In the mic either the transformer or the capsule is connected to pin 2 and 3 and there is no capsule connection to pin 1, which has the negative, Pin one is connected to the case. 

SO there is no complete electrical circuit . SO if you had a miswired cable that had say pin 2 or 3 swapped with pin 1 then you could have problems. (some one wiring up some xlr's and not looking carefully at the pin assignment and wiring the male and female with the connector orientated the same way and forgetting that the pins are swapped


The main type of mic that definitely does not like phantom power is a classic ribbon mic, plug in phantom power and kiss it good by.

Sharyn


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## blademaster (Apr 6, 2007)

*Re: Phantom Power through a Shure BUT*

ok i looked at the mic and the transformer is still there. and the cable is good. (this is a brand new cable, and the other mic still works fine) After I attached the Peavey mic I did not adjust the gain on it.


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## Eboy87 (Apr 7, 2007)

*Re: Phantom Power through a Shure BUT*

I'd still find a cable tester and check that cable. I've gotten some bad ones before from the factory.


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## blademaster (Apr 8, 2007)

*Re: Phantom Power through a Shure BUT*

eboy, if i use another mic with the same cable wouldnt that prove that the cable is still good?


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