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Hi everyone,

so I've owned a Focusrite Scarlett Studio Bundle for around 4-5 years now, but I never had the time or opportunities to actually record something with it other than a few speech samples for courses. In case you're not familiar, the Bundle contains a Scarlett 2i2 audio interface, a Scarlett M25 cardioid condenser microphone and headphones. A week ago I wanted to use it to record a friend for a project and have noticed a large amount of internal noise. It wasn't background noise as it's volume didn't change when I covered up the microphone. I usually turn the headphone (monitor) knob all the way up so that I don't have to increase the mic's gain too much for the speaker to hear themselves and so I can detect any background noise and such. I can't recall if I'd had this noise problem before, but now it's clearly audible when the mic gain is around halfway up and it renders the recording unusable. I can deal with a bad recording environment as I can't help much with that in my current circumstances but this internal noise is ruining everything. It only occurs when I turn on the phantom power for the mic and there is no noise otherwise. I'm currently working on a song with a friend but I can't record vocals until I solve this issue. I used to think the source of it was my laptop or something but I've recently confirmed that's not the case.
Here's a link to a folder on my Google Drive where the 2 sample recordings are. They are the same except for a heavy compressor on the second one which i used to amplify the sound so you can plainly hear it. The gain on the mic was a little below halfway up in the recording and it was really quiet. In some extremely rare cases the noise would stop and the recording would be perfectly clear but only for a few seconds at a time.

Any help is greatly appreciated.

I have the latest drivers and have used Adobe Audition for recording, tried both MME and ASIO drivers for recording.

Link to Google drive:
https://drive.google.com/drive/folders/1kbE5USM9mZiPLDAi63_42_ca333PleHl?usp=sharing

Thank you in advance!

Hi there,

i just checked your testfiles with a spectrum analyzer tool [and listended to them, of course ]. There is some stronger humming in the lower end at 110Hz and 220Hz. Also at 880Hz, but not that strong. But generally speaking a lot of low end hum.
All the way up from there (up to 22Khz) its just the usual "not-that-very-expensive-mic/preamp-noise" that comes with almost every set of affordable gear. My MOTU UltraLite mk3 is also doing that when I crank up the mic gain using the built-in preamps...

Because you mentioned a rare situation, when the noise is stopping for a few seconds i think it could be some interference thing going on...

Of course I have to guess where the hum is coming from in your case... But there are some possibilities:

- interference from a power adapter, creating a hum loop (Notebook or other gear plugged in the same sockets with you interface)

- fan vibrations from PC/Laptop, standing on the same table as you mic stand

- bad power grid interference

- a very rare chance is, that your mic/interface combination is causing the hum (but i doubt that...)

You could try to disconnect your Notebook power adapter and run it on battery while recording (in case you are using a Notebook...)

Test with another Computer/Notebook

Try different power sockets, if possible different power circuits, for computer and audio interface.

Place all gear in your friends home - Same problem?

Disconnect/plug out any unused devices like phone chargers etc. when testing/recording

Try to use some sort of suspension to insulate the mic acoustically from Table and/or floor.

Place the mic away from other gear (like unshielded speakers etc.)

Do some test with other mic/interface/computer if nothing else helps.

When you are able to reproduce the noise problem with other gear, you should probably get to the bottom of the matter...)

Good luck!!

Hi, thank you for your reply.

The test recordings were made in my friend's home in the living room which has a thick carpet and thickly padded furniture. His computer and all other devices were turned off, the windows and doors were shut and my laptop was running on battery power. This was done on my new laptop as I have even worse problems on my old laptop. If I plug the gear into anything that's not a USB 2.0 port, I get even worse humming which is different and louder from this one ( I can provide samples of that as well). The mic was held in hand and as far away from the laptop and the table the rest of the gear was on as possible. Since all the gear I have was bundled together by Focusrite I doubt it's incompatible. The microphone gain was around 50% which produced a very quiet recordibng as you could hear. The other, louder recording is the same except for the compression. I haven't analyzed the spectrum (although I probably should have) but I can hear the hum across multiple frequencies.
I should mention the laptop was set to power saving mode (I assumed it would cut down on cpu and other components' activity) and the gear was plugged into a USB 2 port via a USB hub which may have participated in the hum although I doubt it.
This is rather annoying because I doubt investing in new equipment would yield any better results.

I see many producers recommending the gear I have and using it in their videos on youtube and they get clean recordings with it...

As far as I can tell from the spectrum analysis, the hum is not picked up by the mic itself...

There are some very constant and therefore typical ground-loop-like peaks at the frequencies I mentioned in the first post.

Run an analysis, if possible, and see for yourself.

I think the problem is either related to your notebooks internal architecture itself or the USB hub. If the interface is USB powered, one of those is almost 100% causing the hum after what you described.

Try to plug your interface directly into your notebooks USB port(!) Try all ports available.

If this doesnt´t work, i suggest using other USB cables. Perhaps a shielded high quality cable could also help.

I would recommend using another computer for testing first before buying anything, though.

Hope you´ll solve this soon!!!

Hi a_guy_1

The recording level is very low (-24dB clip) so you're wasting 24dB of headroom and emphasizing the system noise by a good 20dB more than you need to.

Raise the mic gain 20dB or get the vocalist closer to the mic. The noise isn't analogue/thermal noise (like on good old fashioned analogue tape recorders etc) so it's a combination of hum or beating clock noise from around/inside the digital works of the preamp.

Turn up the mic gain and find a different solution to the monitoring problem. Also since all the power is coming thru the USB cable the available power is limited and using less in the phones/monitor circuits just might reduce strain and any spurious digital interference.

Compressing the signal then adding gain amplifies the noise as much as the vocal so wont improve the dynamic range. Using noise removal can improve DR but introduces it's own (often more objectionable) side effects.

Good luck finding the answer,

Wibby

well, the problem with this is the hum increases with the gain so I have no real way of avoiding it. Might be the internals of the laptop since its motherboard got replaced twice in the past month...
I will try to find some more computers/cables/etc to test ecerything out.

Hi a_guy_1

Well your interference is a pretty steady and clean 112Hz + harmonics. This isn't very likely to be AC mains induced. European mains is 50Hz and although the frequency changes with grid load it rarely shifts more than 49.8Hz to 50.1Hz which leave the harmonic at 100Hz +/-0.2. Same in US except centered on 60/120Hz.

The hum on your original recording is only 60dB below clip so it's a good 60dB louder than one should reasonably expect.

If the hum rises and falls in direct relationship to the input (mic) level control then it's certainly being picked up by the mic, mic cable or the analogue pre-amp in the 2i2. The closest likely source would be in the 2i2 interface itself. It's digital circuits are only mm away from the sensitive areas and directly connected by copper whereas the laptop and other stuff is metres away.

Although the phantom supply is common mode, so noise should be self canceling it could be the source if it's faulty. Could be a switch-mode voltage converter running at 112Hz, although I'd have thought kHz more likely. The noise going away when phantom's switched off won't necessarily prove much since the mic electronics will stop working anyway. (I don't suppose there's an easy way to supply phantom to the CM25 from an external battery.)

Try a different mic cable, or if you have an ohmmeter you can check the cable. pin1-pin1, pin2-pin2, pin3-pin3 short, and open circuit between pins 1 and 2 and 3. Also open up an XLR and check the screen is definitely connected to pin 1 and not 2 or 3.

If the cable checks out I think there must be a fault in the CM25 or Scarlett 2i2. Even if there is external interference, laptop or CF lighting, the Scarlet gear should be able to deal with it.

Fingers crossed and let us know,

Wibby.

So today I went to the studio at my university and the engineer there helped me do some testing.

The microphone and its cable are most likely not the cause of the problem as they worked perfectly fine when plugged into another, high-end audio interface. However, when we plugged them into my 2i2 and my laptop (running on battery) we got a different kind of hum which I only get when I plug the interface into a USB 3+ port except now it was happening on a USB 2 port. The weird thing is, the hum wasn't constant nor consistent - unplugging and plugging the microphone back in triggered it but then after a while it stopped and reappeared again after some more disconnecting/reconnecting. There was no discernable cause or reason for it, it just kept randomly happening and disappearing. It also varied in intensity and frequency a bit.
One possible cause suggested was a bad usb cable that came with the interface but changing that did nothing.

One other thing: the line-in/instrument switch does NOTHING to the gain on either input channel and the gain itself seems to be really quiet until around 3/4 of the way up where it suddenly increases disproportionately (a small increase increases the level significantly). Is that behavior normal for the 2i2 (1st generation)? I can't remember if the gain worked like that before but I think it did not. The quiet (original) recording linked in this thread was made with the gain at around 50%. Shouldn't that be much louder?

Oh and we couldn't reproduce the exact type of hum heard in the test recordings.

I am really lost here...

Hi a guy,

I'm afraid I know nothing about the Scarlet 2i2 except what I found online. (I was an analogue audio designer last century, so my knowledge of digital recorders is generic and limited, hence my thoughts centred around the analogue aspects of the input stage.)

I downloaded the user manual and had a good read. The Line/Instrument switch only works to change the impedance/gain at the jack input. So it won't affect the mic (XLR) - all normal on your box.

If input gain control is set around centre with the scarlet mic a headroom of 20dB seems about right for a semi-log/s-curve law potentiometer. Level depends on vocalist and distance from mic. I'd think 100cm to 150cm from mic might peak at -15 to -5dBFS @ centre settings, (I'm not a recording engineer so I hope a real recording guy/gal will correct me because I'm probably wrong.)

If problem is triggered by plugging/unplugging the mic it sounds like a 'motorboating' instability. This typically happens when a faulty or missing decoupling capacitor on a power rail causes an oscillation. This can be triggered when a signal gets louder and more current is demanded. Once it's started feedback keeps it going until it's stopped by another transient signal or power event.

Even the crappiest USB cable and computer shouldn't trigger this kind of noise - unless the computer USB port +5v can't supply enough current. The 2i2v1 tech specs don't mention current requirements but they must be lower than USB2 spec.

Could try test recording a line signal (via jack) to see if sensitivity is what you'd expect and if it has buzz as well. If line is okay then fault is in the mic pre-amp stage. If line has same symptoms then fault is in line-amp stage/AD converter (common to both mic & line).

Try test recordings at different sample rates - see if anything changes.

I can't see how a problem at the computer end would depend on the input gain setting or would trigger this. But I can see how powering up and down v USB changes might randomly trigger things, but the fault would still be in the 2i2.

Well that's all my ideas I'm afraid, my knowledge being limited to google, youtube, and stuff from the 1990s.

Perhaps a visit to www.focusrite.com/answerbase or see if Focusrite will respond to an e-mail.

Anyway, good luck

Wibby

Thank you for your feedback Wibby.

I found out about the line/instrument switch today as well. I also called the store where I bought the bundle and am taking it there tomorrow to have a look.
Will report what transpires.

Thanks to everyone for responding!

Time to conclude this thread.

I would've done it sooner but real life got in the way. Anyway, I took the bundle the the store where I bought it many years ago and for whatever reason it just worked. Everything worked just fine... The USB 3 does cause some annoying low frequency hum but that's only when I turn on the phantom power (regardless of the microphone being plugged in). So I dug up a very old crappy dynamic microphone. It was a Singstar microphone for the Playstation 2 which a friend gave me around 11 years ago and which I never used. I plugged it in with a quarter inch adapter and it worked surprisingly well. The audio quality was nowhere near the Focusrite mic's but it was more than usable and since it doesn't utilize phantom power, it had no hum whatsoever even on the USB 3 port.
I have no idea why everything decided to work but it just does now so...

Thanks to everyone who replied for your effort.

Glad you got it sorted a_guy.

If you ever get a chance to borrow a different phantom powered mic you might be able to check if the problem's in the 2i2 phantom supply or in the Scarlet mic.

Thanks for letting us know.

Happy recording

Wibby.

Actually I'm certain it's the phantom power in the 2i2 that's causing it. The hum happens even when I have a dynamic mic plugged in and phantom power turned on. It happens if I increase the gain on any channel even if nothing's plugged in it.
By the way, I just submitted 3 sounds made from the test recordings on a crappy dynamic microphone so you can check them out though I overdid the EQ a bit...

I also figured a dynamic mic like a Shure sm58 would be better for my horrible recording environment so I'm looking into buying one.