Hey guys,

Sorry for the begginers question, i've tried searchin a myriad of forums to asist me but have just found my sef confused. I am currently running an sm57 directly into a ur22, however i have found that in order to get an audible signa', the gain reaches a point of hum.

What do I need to peform, or aquire to rectify this issue?

I think you already know this, but the SM57 isn't the source of the hum. But its need for preamp gain is exposing the hum that's already there.

Assuming the hum isn't a design feature of your interface, the right thing to do would be to eliminate it by finding the source. Hard to say what that is, most likely a grounding issue, and at any rate beyond the scope of this thread or at least the scope of this post.

The band-aid fix is an in-line mic booster like a Cloudlifter. With one of those, the hum will still be there but the mic will be 25 dB louder, making the hum effectively 25 dB quieter.

Remove your 57 and the cable and turn up your interface. Is the hum still there? If so Brent is right. It's a interface issue. If not, then swap out your cable for a new one. If still there swap out your mic. Last resort, put a ground lift plug on your ac line and plug it in. Lifting the ground can sometimes clear it, but I wouldn't recommend running it that way. If the ground lift clears it, then you have a issue in your electrical wiring. Deal is, you need to determine what is causing the issue before you can rectify it and to do that you need to swap out the different potential offenders until you figure out where the issue is.
L.

It's also possible that the 57 is picking up interference...if pointing the mic in a different direction or walking around the room changes or removes the hum, that is the problem.

Make sure your mic is well away from any mains transformers (internal or external power supplies).

Usually when a system hums it's because it doesn't know the words...

Try different mics & cables to make sure it isnt a specific piece of gear with a ground or shield problem.

Sperry GFCI Outlet Tester-GFI6302 - The Home Depot

Make sure you turn on the +48v on the mic pre. if the hum is still there, check all gain sages and make sure your electrical is grounded.

What purpose does turning the phantom on serve?

With a sm57, it will ignore it as the sm57 doesn't need phantom power. But im trying to see if your interface is defective, or your mic is defective or if its user error

Not my interface. Mine are good but thanks for the answer

Hi,

to rehash this thread. I recentlry tried recording my ac15 with an sm57 and when close to the amp the 57 picks up lots of hum. I love the sound of the 57 on the amp so I was wondering if there are any solutions?

Sounds to me like the amp is humming not the mic. AC hum is common with high gain amps because they contain so many stages, any low levels of AC EMF get amplified to audible levels. Any gain pedals and their associated power sources can be the cause, any cord and the guitar itself, especially guitars with single coil pickups or fender guitars that are wired with unshielded wires.

The reason you hear it when recording is because your ear isn't directly in front of the speaker like a mic is. if you're micing an amp sitting on the floor, all your hearing is the indirect sound reflecting around the room. You want to either tilt the amp back at your ears or raise it up to ear level so your ears hear the sound beaming at them directly like the mic is hearing it. If there's hum there you'll know it. You can then dial up tones and gain levels that help mask the problem. Make sure the room doesn't have dimmers or florescent lights too. Finding the source of hum is like being a detective. you need to rule out causes one by one till you find the cause. Even then it might be staring you right in the face but you're unwilling to deal with it.

Hum can also come from the tubes needing to be biased if its a tube amp or from a ground loop. Sometimes just getting your computer and all gear on the same outlet ends all hum problems. Generic wall warts is a big one. Boss pedals need zero hum wall warts or the will hum both on and bypasses because they are not true bypass, they are buffered pedals which are always on. Cheap guitar cords are a huge cause of hum. Cords with 75% shielding may be OK plugged straight into an amp with no pedals, kick in a drive pedal and they hum like a banshee. You want to use cords with 90% copper shielding or better. A noise gate/Hush pedal can do wonders quieting hum when you stop playing.

The guitar itself can have either copper foil or conductive paint added to ground the hum out. Inexpensive guitars can usually be helped with this quite a bit.

The interface itself may be humming but the likelihood is pretty low. The preamps in it are not exactly high gain so I cant see them raising any kind of hum up unless its being fed that hum at its input. If anything you may hear some hiss when the preamp's maxed out but hum is unlikely. If the unit uses and external wall wart then make sure its the right one. If the current isn't right or its not smoothing the DC you may get it to leak into the circuit.

If the units getting pure DC there's no way the unit should be humming unless its a piece of crap poorly designed and lacks shielding. Even then its more likely an environmental issue overcoming the unit, not the unit itself generating it because the unit is DC, not AC. If you have a higher end interface with an AC to DC power supply built in and the units getting older then maybe the smoothing caps are getting old.

The mic itself? I've used SB57's for 50 years never had one hum, ever. The cables? Sure a bad cable or connector with a bad ground could do it but you'd likely be loosing allot of signal gain too. Mic cable qualities are usually pretty good even with the cheaper ones. Main differences being how strong the signal winds up being and how durable the connectors are. The mics themselves are housed in a huge chunk of metal. There no way you can get hum to penetrate it if its grounded. A bad wire inside it would go dead, not hum.

Hi!

I appreciate the response and there indeed is some hum in my amp. However, this is not the amp. I did put my ear against the amp and have done the same thing with my m88 (which doesn't hum), the sm57 when placed next to the amp just starts buzzing and i mean VERY close to the amp, almost touching, it is very noticable and happens when only when I put the sm57 touching. its a low frequency hum and cuts off at about 200-400hz if i remember correctly.

It could also be a grounding issue. I will check that, I have had some issues with my 500 series chassis recently and these are DIY preamps, so I will do some troubleshooting.

Thanks

The voice coil of the 57 will pick up hum, perhaps from the mains transformer of a yr amp. Can you try running the amp into an external cab and micing that? Get it a couple of yards away from the amp. Do you still get hum?

Edit: I think the M88 has a humbucker coil - which might explain why you don't have the problem with it.

turn the screw holding the XLR connector in the microphone clockwise till it stops.
ease out the connector and photograph the connecting wires and their solder points.
then upload the image.

I don't have another cabinet to test it. But yeah, The hum is at its most intense when the mic is close to the tube circuitry (which I am guessing is close to the transformer). At the bottom left of the amp the hum is least noticable. So doo you think this is the case? and if so, how do so many people close mic their amps with sm57s and not experience this?

I don't see a 3rd connection?

But looks like its soldered to the metal plate

I'm almost certain that this is the issue. But I've never used a ac15 ( I got a monster shock of an old ac30 once ). As to how folks dodge the hum, I dunno, I guess some amps are worse than others?

Did you buy the ac15 new? If not, has the mains transformer been replaced? Any other mods?

[edit] and casting my mind back to that shock - does the amp have a good ground / earth?

This is what you'd expect. It's how the case is connected to the cable shield. This screens the internal wiring (and the transformer) of the 57. The voice coil is not well shielded (it's within the plastic bit), so if the mains transformer of the amp isn't shielded either - it's a recipe for hum.

not sure if yours has a transformer or not. I think what you may find, is that if you disconnect pin 1 from the tab (assuming it's been soldered to the tab) the hum may well stop.

that should be similar to taking an xlr cable and disconnecting pin 1 at the end you put into the microphone. a cable like that is a handy test cable to have, because it saves you doing something inside a microphone. it can just be a pretty short cable you use for that purpose. the cable itself can provide a test condition. you then can take some white shrinkwrap or tape and put it round the connector, and write on it that pin 1 is disconnected.

consumer and prosumer pieces of gear can exhibit these hum conditions, even when they are battery powered. so it can appear in gear where there's little risk of electrocution. the other reason that cable can be handy, is because if you are working in a low risk setup, it can be used to get the job done while you maybe investigate it further.

things worth knowing, are the electrical integrity of a cable. for which a cable tester can be handy. and if the tester provides continuity tester probes, you could disconnect your soundcard completely and then test if pin 1 on the xlr sockets have continuity to the chassis. either at the input end or output end. this provides useful information. even if you figure out you can't solve something, you have some clues as to why you might not be able to. so you provide yourself with more chances to solve it eventually.

Ever stick them in a Leslie? I've had them hum in that scenario, and would guess this likewise is a case of interference pick-up. 58's are susceptible to this also IME. Mics I use instead which seem to perform much better in this respect are M88, 421, 441, RE20 (original version), M201, etc. YMMV. Good luck.

Yep, they've all got humbuckers, I think. If the excessive hum isn't down to a fault on the amp (or even if it is, I suppose), then any of these would work. Unless you're hooked on the 57 sound. Check the grounding's good on that amp tho'.

Hi jonnie. Thanks for the suggestions. Yeah I'll definitely try to get the grounding checked out. Anyone have any idea how to test grounding on an ac15? I also don't know the history of the amp as it got switched with someone else's of the same model a long time ago and we never switched back. But I have never had any real issues with it

Lets get this straight: an SM 57 is a dynamic mic with a single voice coil, thus susceptible to picking up magnetic fields ( 50 or 60 cps mains hum).

A vox ac15, or any valve amp for that matter, not only has the power supply transformer generating a powerful magnetic field, but also an output transformer .

Either move a dynamic mic out of the magnetic field, or use a condenser mic
to close mike a guitar amp. Condenser mics are not prone to induce hum from a magnetic field.

At my job, we usually use AKG 414s to close mike a guitar cab, but they are a bit pricey. An AKG C1000, Rœde NT1, cheap knockoff or el cheapo Electret mic will do better in fording off EMI than any dynamic mic will.

And make sure your mic cable is balanced.

Just my 2c

I am not an electrician or an amp doctor.

What I do (with any pre-owned electrical gear) is open the mains plug and check the earth is connected, then check the resistance between obvious exposed bits of metal and the earth pin on the mains plug, WHILE UNPLUGGED. With an amp - that'd be the chassis, any metal switches and, if accessible, frames and shrouds of any transformers. I'd want to see very low resistance between them and the earth pin. Less than 1 ohm. Any doubt, ask an amp doctor.


the c1000 is a cracking mic for amps, I've used one for years, and you can pick them up pretty cheap.

Almost every time (when used on a Lesli). It emanates from the amplifier section. I've taken to either placing the lo mic on the other side if possible and being careful of my cable routing. It keeps it to a minimum. Yup Noisy things those Leslie's are but they sound so good overdriven .

The UR22 has a well known hum problem with certain computers / power supplies. It is especially bad when using phantom power but shows up even with dynamics and DI. Steinberg offered to pay for replacements and shipping, then came out with a MKII.

My UR22 mk1's hum is much much worse on my desktop as compared with my laptop. I have recorded with a 57 on my laptop and still encountered some problems, which I was able to minimize by

1) cranking the gain on the guitar amp so that the interface gain was 0

and

2) experimenting with positioning the mic and wire and their directional facing

I purchased three SM57’s within the last two months. One from Amazon, and the other two from Sweetwater very recently. I just tried the two new 57’s and they have noticeable hum at full preamp gain. I then tried the Amazon one, and the same thing. I compared all these to a 57 that I had purchased a year or two ago. No hum, or very very slight. An absolutely noticeable difference. These were tested using the same pre, cable, position, and gain in the comparison.
There you have it folks, it is the microphones after all, in this case.