SM57 buzz/hum issues

[piotr]

Hi,

Some time ago I got a pair of SM57s with the TAB mod from Mercenary, and I do really like the mics. I did notice though, that they are very sensitive to some kind of interference. As I move the mics around in the studio, I can distinctly hear an electrical sounding buzz/hum come and go in specific spots/locations. Sometimes in a particular spot there will be no hum, but just tilting the mic up or down will bring up the buzz. This is something I do not experience with other mics in same situations, and seems to be unique to SM57.

Also I want to stress that this is not about noise floor of the microphone itself, but a kind of distinct buzzy hum that is audible only in certain situations: perhaps responding to power lines or magnetic fields?

So here are some questions to start with:

Did anyone have similar experiences with SM57s?
How would you guys suggest dealing with this?
Are SM57s more susceptible to this kind of interference?
Could this be related to the TAB mode?
Or do you think this is cable related?
Other?

Any thoughts/feedback will be appreciated.

Sincerely,
p.

PS

Just for the record, I also want to say that I have indeed done extensive searches regarding the SM57 on Gearslutz. There is a gazillion threads about this microphone covering various aspects of it. But very little is said about noise/hum issue I am asking about.
For example, there is a mention here by owel that seems to describe exactly what I am talking about. Or this thread from 7 years ago, which no one responded to...

[mikethedrummer]

Is all of your tracking equipment in the live room with you? Mics and cables don't play nicely with electronics. Try isolating if possible. I've also heard of people picking up noise such as radio traffic. The way to fight these things is to isolate the room and condition the power, both of which are very expensive to do right.

[piotr]

Originally Posted by mikethedrummer

Is all of your tracking equipment in the live room with you? Mics and cables don't play nicely with electronics. Try isolating if possible. I've also heard of people picking up noise such as radio traffic. The way to fight these things is to isolate the room and condition the power, both of which are very expensive to do right.

Hi,

Thanks for the note. Yes: everything is in the same room: my sound studio, my art studio, my library, my workshop...

I am not picking up anything else: and never had this problem with any other piece of equipment in the studio (or other mics). Which is what got me wondering whether there is anything particular about the SM57s that brought this issue to light in my circumstances.

Regards,
p.

[piotr]

Does anybody else have any thoughts/suggestions on this matter?

p.

[piotr]

So nobody had experienced similar problems with these mics?

Hmmm...

p.

[Les]

The 57, like many dynamics, has rather low output.

It does not have a hum bucking coil as some others do.

So it is somewhat suceptible to noise pickup, Particularly near amp power transformers and the like.

I do not think the TAB retrofit would effect this much.

It's there, but not usually an issue for me since I am close micing drums and loud guitar with the things.

Let me ask this: What ae you trying to mic? Is it a very quiet sound?
If so, I might have some suggestions to make the buzz go away.

[piotr]

Originally Posted by Les

The 57, like many dynamics, has rather low output.

It does not have a hum bucking coil as some others do.

So it is somewhat suceptible to noise pickup, Particularly near amp power transformers and the like.

I do not think the TAB retrofit would effect this much.

It's there, but not usually an issue for me since I am close micing drums and loud guitar with the things.

Let me ask this: What ae you trying to mic? Is it a very quiet sound?
If so, I might have some suggestions to make the buzz go away.

Hi Les,

Thank you for your feedback.

I have tried the mics on a variety of things: but I did notice the issue most when recording a fairly quiet pizzicato on a cello. Then I moved the mics around the studio, and realized that there were some spots that produced a fairly loud buzzing sound (as described earlier).

I am curious to hear your suggestions for recording quiet sources with SM57...

I am using a Mogami shielded quad cables with these, which have served me well with other mics: would using a cable with terminated ground make any difference here?

I appreciate any thoughts on the matter.

Sincerely,
p.

[Les]

Hi Piotr

Interesting mic choice for a cello. Neat! Love to hear a clip.

You're probably getting sub millivolt levels from the mics, so even a microvolt of hum pickup would be only 60 db down...easily audible.
Sure not like getting half a volt with a condenser mic near a drum kit!

This caught my eye because I have designed a preamp model specifically for low output dynamics and ribbons. I'm testing it now. Hum and buzz from the mic and pre become a big, big issue. I'm trying to develop a system that makes this common problem completely go away.

As for your situation, you describe a buzz sound... that implies the source is something doing rectification or rapid mains switching. Lots of harmonics.

Won't hurt to use a mic to "sniff" out big electromagnetic sources. Possible candidates are big power amps, phase control light dimmers, flourescent lights. If you find one , turn it off or move it.

Your mic cables are good quality...very good common mode rejection. It's funny...sometimes with poorer quality cable you can wrap it in loops and tape it somewhere near the mics oriented such that it forms a crude hum bucking coil!

Of course you can orient the mics/instrument to minimise the buzz, but that might result in a position that has poor acoustic pickup.

You can rotate the mics in the holder though. Try that. Hum pickup is not axially symetrical.

Yes, you can mess with ground lifting. As an electronics engineering type i'm not too fond of the concept...but I acknowledge it helps sometimes, mostly due to improperly designed gear.

Try these things. I do have other ways that can eliminate the buzz, but can't talk about them yet. I can PM you concerning that if you want, if the above mentioned methods don't help.

Minneapolis, huh? I used to go up to the old Sound 80 studio there a lot. I hired Orfield labs to assist in some of my acoustics work. Nice place.

[mattg082]

you would be surprised how easy it is to pick up noises with the mic cable and equipment near each other like another person said. i had just bought a lunchbox, rosetta and a few new mics and started having this issue with some things. low and behold moved the pres, volume att and rosetta away from eachother and kept moving the chord around and it went away... same thing happened in another room doing a mobile recording. It only happened when I got the new gear and used a 57, sm7b and re20 from time to time. It was fixed though by seperating things a bit and picking racks up and moving them a little till it went away. I was really surprised and never had that issue.

[eascholz]

I'm actually away on Spring Break right now. I brought an sm57 and an MBOX just in case we had to make some music.

Sure enough, when we were doing a bit of recording, the sm57 did a superb job of picking up interference from my mackbook charger. It was just as you described: a buzz. I should also note that this is through the MBOX preamp, which has an input impedance of 9,500 ohms. This is super high; way too high for an sm57 in my opinion. In turn, with a high impedance preamp, the sound is more detailed, but tends to be harsh in the highs.

I would definitely try using a preamp with switchable impedance as a lower impedance will probably make the mic less sensitive to any type of interference. For me, I hadn't previously noticed because my sm57 is usually stuck on a guitar amp, routed through my LA-610.

[piotr]

Originally Posted by Les

Hi Piotr

Interesting mic choice for a cello. Neat! Love to hear a clip.

You're probably getting sub millivolt levels from the mics, so even a microvolt of hum pickup would be only 60 db down...easily audible.
Sure not like getting half a volt with a condenser mic near a drum kit!

This caught my eye because I have designed a preamp model specifically for low output dynamics and ribbons. I'm testing it now. Hum and buzz from the mic and pre become a big, big issue. I'm trying to develop a system that makes this common problem completely go away.

As for your situation, you describe a buzz sound... that implies the source is something doing rectification or rapid mains switching. Lots of harmonics.

Won't hurt to use a mic to "sniff" out big electromagnetic sources. Possible candidates are big power amps, phase control light dimmers, flourescent lights. If you find one , turn it off or move it.

Your mic cables are good quality...very good common mode rejection. It's funny...sometimes with poorer quality cable you can wrap it in loops and tape it somewhere near the mics oriented such that it forms a crude hum bucking coil!

Of course you can orient the mics/instrument to minimise the buzz, but that might result in a position that has poor acoustic pickup.

You can rotate the mics in the holder though. Try that. Hum pickup is not axially symetrical.

Yes, you can mess with ground lifting. As an electronics engineering type i'm not too fond of the concept...but I acknowledge it helps sometimes, mostly due to improperly designed gear.

Try these things. I do have other ways that can eliminate the buzz, but can't talk about them yet. I can PM you concerning that if you want, if the above mentioned methods don't help.

Minneapolis, huh? I used to go up to the old Sound 80 studio there a lot. I hired Orfield labs to assist in some of my acoustics work. Nice place.

Hi Les,

Thank you for your thoughtful and thorough response. It looks like a number of good suggestions I will try in the studio, and I will report back on my findings.

Rotating the mics sounds like an interesting observation that did not occur to me. I noticed that the buzz would come up as I tilted the mic (angled up or down) in particular spots. I did not think of rotating the mic... it sounds so simple, and if that simple trick would work it would be fantastic!

Finding buzz-free spots in the studio, of course, is a solution, but I started this thread hoping to learn a bit more about why and how this problem occurs. Posts such as yours make gearslutz such an invaluable resource: thank you again.

Your development plans sound intriguing.
And it made me think that an important thing to further investigate my situation, for the moment, will be to try all different preamps and see if I can identify most "offensive" circumstances.

I should invest some time in the next few days to look at this more closely.

Sincerely,
p.

[piotr]

Originally Posted by mattg082

you would be surprised how easy it is to pick up noises with the mic cable and equipment near each other like another person said. i had just bought a lunchbox, rosetta and a few new mics and started having this issue with some things. low and behold moved the pres, volume att and rosetta away from eachother and kept moving the chord around and it went away... same thing happened in another room doing a mobile recording. It only happened when I got the new gear and used a 57, sm7b and re20 from time to time. It was fixed though by seperating things a bit and picking racks up and moving them a little till it went away. I was really surprised and never had that issue.

Hi mattg082,

Very interesting!
And it sounds very much like my situation: and much like you, I only started hearing this problem when using SM57...

Thanks for chiming in!

And I was starting to think that I was alone in this!
It is a bit weird that for hundreds of posts related to SM57, there were so few reports of similar issues. I suppose many people do not experience the problems, or find them marginal when micing loud sources etc. But still...

p.

[piotr]

Originally Posted by eascholz

I'm actually away on Spring Break right now. I brought an sm57 and an MBOX just in case we had to make some music.

Sure enough, when we were doing a bit of recording, the sm57 did a superb job of picking up interference from my mackbook charger. It was just as you described: a buzz. I should also note that this is through the MBOX preamp, which has an input impedance of 9,500 ohms. This is super high; way too high for an sm57 in my opinion. In turn, with a high impedance preamp, the sound is more detailed, but tends to be harsh in the highs.

I would definitely try using a preamp with switchable impedance as a lower impedance will probably make the mic less sensitive to any type of interference. For me, I hadn't previously noticed because my sm57 is usually stuck on a guitar amp, routed through my LA-610.

Hi eascholz,

Thank you for your post. Mac power supplies (and even the internal wiring of the laptops) is known to cause some interference issues. I noticed (unrelated to SM57) huge issues when using a USB interface with a mac laptop: buzzing etc. A mac specialist opened the laptop and showed me exactly how the power supply wires are running literally right next to the USB input, which seemed crazy. For the project I was working on, and interface I was using this was a real issue.

Now, in my studio I don't use the laptop, so in my case the problems with SM57s were not related to mac power supply, but it could have been the proximity of power supplies for some preamps, or compressors.

The impedance is another thing I should look at more closely, and experiment with different settings.

Thanks for all the comments and suggestions!

Sincerely,
p.

[Spindrift]

I have this same problem. Solved by putting the headphones on, cranking the gain and using the mic to hunt for hum...then I stay away from found hum! I've noticed it on 57s and SM7b's to. I'm using a Duet tonight but I've heard the hum through one of my 512c pres too so it's something to do with the 57 coils for sure.

My windscreen (or cover or whatever) is really really loose....it's a relatively new 57 too.

Oddly, the 57 is no slouch on acoustic gtr (through a nice pre) if you're going for a certain sound. I happen to like that sound....

Keith

[A4722]

Originally Posted by eascholz

...I should also note that this is through the MBOX preamp, which has an input impedance of 9,500 ohms. This is super high; way too high for an sm57 in my opinion. In turn, with a high impedance preamp, the sound is more detailed, but tends to be harsh in the highs.

I would definitely try using a preamp with switchable impedance as a lower impedance will probably make the mic less sensitive to any type of interference. For me, I hadn't previously noticed because my sm57 is usually stuck on a guitar amp, routed through my LA-610.

Excellent angle to approach the problem from !!!!

[YRLK]

Originally Posted by piotr

So nobody had experienced similar problems with these mics?

Hmmm...

p.

I definitely have, man. I never realized how noisy SM-57's are until I tried using them on a fairly quiet/breathy vocal tune a few months ago. Obviously, this is not the typically advertised application for the 57, but I wanted sort of a low-fi vibe sound, so I tried it out.

The sound was pretty much how I wanted it through the right pre and a nice compressor; however, in the end, I had to scrap the takes because without much more than an acoustic guitar in the song, the hum definitely stood out.

Out of curiosity, I tested several other mics to see if I could get a similar effect - and to see which would be quiet.

An RE-20, SM7B, and Beta 52 (only to test it for noise, not actually for vocals!!!) all yielded about the same result... cool, old-school sounds, but too noisy (and specifically, HUMMY/buzzy).

The Heil Sound PR-30 and Sennheiser E-906 were both VERY quiet microphones and could easily have been used. I may end up using the E-906 for this application and using the low-pass / hi-cut filter on it for more of a low-fi sound, but as expected, the Heil PR-30 didn't make the cut because it's a much more brilliant sounding mic in high frequencies... the Heil line is anything but low-fi. =) *But on another note, the PR-40 probably remains the BEST mic for kick drums I've ever used. It's really remarkable.

So yes, I have experienced the same issues, and it's not the pre or power supplies or electronics being low quality or in the wrong place... it's just that the SM-57 is not a very quiet microphone. I'm not sure why this is - maybe it could be shielded somehow... I don't really know. But it doesn't surprise me to hear that the TAB transformer upgrade doesn't really solve this problem either. What DID surprise me was that the SM7B didn't really make any improvement either.

Low output mics, I guess.

In contrast, my Korby with a tube circuit and extra cable going to its separate power supply and then one going back out into the pre: it's one of the quietest mics I've ever heard! So go figure. =)