SOUND ON SOUND

[chanyam]

Hi all,
I'm a totally noob trying to learn some of the ins and outs of recording audio. Specifically, I want to record acoustic guitar to send to my guitar teacher as we're still not doing in-person lessons due to covid.

Anyway, I don't have crazy aspirations of producing professional music, I just wanted to be able to make a quality recording and so I got a Samson C01 condenser mic and a Presonus Studio 24c. After hooking it all up and making some test recordings, I've found a few things that were unexpected (at least to me).

1. I don't get any audible output unless I turn the gain way up on the mic output and by way up I mean I literally hear nothing until the gain knob is about 3/4 of the way to max and its incredibly quiet unless I basically max the gain. This brings me to my other issue.

2. There is a high pitched whine in the audio. It kinda sounds like the ringing in my ears I used to get when I willingly damaged my hearing going to Megadeth concerts when I was young :)

The first issue, from what I've read is pretty common so not sure there's much to do there. The second one is strange and I'm not sure what to do with it. I tried reading up on it here and on other forums and these are the things I've tried to do to solve the issue and\or narrow it down to a certain cause:

* I've tried turning off everything I don't need to have on in case it was a ground loop issue. Turned everything off except the PC, one monitor and the interface.
* Switched to my laptop running off of batt with the interface plugged directly into it (no powered USB bus)
* switched headphones
* switched USB cables
* switched the XLR to the other input

None of those have worked. The noise comes through recordings made in OBS and Windows Camera App. If I plug headphones into the interface, I don't hear any whine - just room noise, which I expect.

I haven't tried swapping the mic or the XLR cable (haven't had time yet). Before I go spend more money, I thought I'd check in with this forum.

My setup is as follows:

Windows 10 PC with all the latest updates
Samson C01 plugged into interface via XLR
Presonus Studio 24c interface plugged into PC via USB
Recording with OBS and Windows Camera App
My interface has 48v phantom power for both inputs and its on

does anyone have any ideas on what this whine is and what else I can try to fix it or at least isolate what the issue is? I'm happy to upload an audio file demonstrating the issue and posting the link if anyone thinks that would be helpful.

Thanks in advance!
-C

[James Perrett]

Just to clarify - monitoring via headphones directly through the interface is fine. That means that the mic and cable are OK. How about monitoring with headphones with the audio going through your recording software rather than direct?

[wireman]

When the headphones are not plugged into the interface how to you hear the sound? Can you hear it output while you are recording or only on replay?
When the headphones are plugged into the interface does the recording have the noise in it?

[chanyam]

wireman - when the headphones are not plugged into the interface, I hear sound when I play back the recording the audio is output to a different pair of headphones connected to my PC (USB headphones in case that's relevant).

James - so, in getting the answer to your question I found noticed something: I don't hear any whine when monitoring from the interface directly unless I have OBS open and have added the interface\mic as an audio input. If I have OBS open and the interfac\mic added as an audio source, I hear the whine in both recordings and monitoring the interface without recording anything in OBS. As soon as I close down OBS, the whine disappears. I tried a similar experiment using Windows Camera App. It was similar - the difference being that I didn't hear the whine until I actually pressed the record button. Once I stopped recording, the whine disappeared. In OBS, it didn't matter if I was recording or not.

One other thing I forgot to mention in my original post in case its relevant is that I don't have a discrete audio card. I'm using the on-board audio card (realtek chipset I think). I don't know how involved or where the PC's audio processor comes in (like I said, I'm a total noob) but I thought I'd call that out in case it was relevant.

Thanks!

[chanyam]

So I found a fix....sort of.

If I take the main out or the microphone out from my interface to an analog input to my on-board sound card, the whine goes away! So it seems like its has something to do with the A-D conversion from my interface over USB....? Not sure what to do with that. I guess a good question is: do I need to or should I just record using this crazy (to me) setup? To recap, now my setup is this:
Samson C01 XLR mic into Presonus Studio 24c interface to sound card mic-in from mic-out on interface.

Why did I use the mic-out and mic-in instead of Mains out and line-in? I found that, for whatever reason, using Mains out to line or mic in on the sound card produced low levels. If I used Mic-out then I could max the gain on the mic and and the mic-in on the sound card for whatever reason produced a louder recording. I'm not sure how I'd monitor my recording audio now that the mic-out is tied up sending audio to the PC. Maybe use the Main output? Then I wouldn't be able to mix input with playback but I don't really use that feature now anyway.

So getting back to the whine using the USB connection - is this common? If so, is there also a hopefully common way to resolve this?

Also - kinda unrelated, is there some way to to boost the pre-amp (again, sorry if my terminology is wrong, I'm still trying to learn everything)? It seems like needing to max my gain to get anything like a usable level of output means that my preamp isn't sufficiently powerful enough to power my condenser mic and also leaves me zero headroom so I'd love to find a way to get a decent recording level without having to be so high up on the gain.

Thanks!

[James Perrett]

So I found a fix....sort of.

If I take the main out or the microphone out from my interface to an analog input to my on-board sound card, the whine goes away! So it seems like its has something to do with the A-D conversion from my interface over USB....? Not sure what to do with that. I guess a good question is: do I need to or should I just record using this crazy (to me) setup? To recap, now my setup is this:
Samson C01 XLR mic into Presonus Studio 24c interface to sound card mic-in from mic-out on interface.

Why did I use the mic-out and mic-in instead of Mains out and line-in? I found that, for whatever reason, using Mains out to line or mic in on the sound card produced low levels. If I used Mic-out then I could max the gain on the mic and and the mic-in on the sound card for whatever reason produced a louder recording. I'm not sure how I'd monitor my recording audio now that the mic-out is tied up sending audio to the PC. Maybe use the Main output? Then I wouldn't be able to mix input with playback but I don't really use that feature now anyway.

So getting back to the whine using the USB connection - is this common? If so, is there also a hopefully common way to resolve this?

Also - kinda unrelated, is there some way to to boost the pre-amp (again, sorry if my terminology is wrong, I'm still trying to learn everything)? It seems like needing to max my gain to get anything like a usable level of output means that my preamp isn't sufficiently powerful enough to power my condenser mic and also leaves me zero headroom so I'd love to find a way to get a decent recording level without having to be so high up on the gain.

Thanks!

It is good to hear that you have a solution - albeit unconventional. It does seem that there is a problem with your interface. Do you have something else that you could plug into the interface and try recording to see if the noise is still there? If the whine is still there then it points to a faulty A/D convertor chip. I've experienced low level tones (known as idle tones) from a budget A/D convertor but not at a level which would be a problem in normal use.

Don't worry about the gain issue - this is simply a by-product of having a gain control covering a very wide range where the part of the range that you need to use is crammed in at the top end of its travel. The preamp isn't 'weak' or more likely to clip than a better designed preamp with a more sensible gain range. Just make sure that you record at a sensible level with an average level of between -24 and -18dBFS and peaks at no more than -12dBFS. This gives you plenty of headroom for the odd unexpected peak and further processing. You can adjust the level for your final files at a later stage.

[chanyam]

James - I plugged my phone via 1/8" connector into input 1 on the interface using a 1/4" adapter and then recorded a video's audio off of youtube in OBS. The interface is back to being connected to the PC via USB. The recorded audio doesn't display the high pitched whine. The audio sounds like its being captured from inside of a pint glass, but other than that, its fine :)

I'm not sure where that leaves us...does that mean that it is the mic or XLR cable? Something else?

[Sam Spoons]

Are you using a TRS mini to TRS ¼" cable? That would explain the 'audio in a beer glass' sound (love the description :D ).

[ef37a]

What happens if,..
You have nothing plugged into the interface, advance the gain to where you usually have it with phantom power switched on. Record.Then repeat the exercise with P power off.

A 30 second recording each time will be enough. The result should be a noise, hiss at around (total guess) -80dB fs. Most importantly there should be no sign of any whine.

If plugging the mic back in produces the whine again? Well I am sure you are ahead of me!

Just looked up the mic's specifications and find it has a sensitivity of -33dB making it a mid to 'hot' microphone and should not need much gain on the AI. Much depends however on your expectation. For 'musical' purposes the DAW meters should bumble at around -20dB fs. If you are striving for -6dB ish then yes, you will need to crank the gain but for digital recording you don't usually need to be nearly that hot.

Dave.

[chanyam]

Are you using a TRS mini to TRS ¼" cable? That would explain the 'audio in a beer glass' sound (love the description :D ).

I had to look up what a TRS cable was :D. Yes, TRS 1/8" cable (came with the headphones) to a TRS 1/4" adapter. Now I'll have to look up why that produces that echoey beer glass sound :)

[chanyam]

What happens if,..
You have nothing plugged into the interface, advance the gain to where you usually have it with phantom power switched on. Record.Then repeat the exercise with P power off.

A 30 second recording each time will be enough. The result should be a noise, hiss at around (total guess) -80dB fs. Most importantly there should be no sign of any whine.

If plugging the mic back in produces the whine again? Well I am sure you are ahead of me!

Just looked up the mic's specifications and find it has a sensitivity of -33dB making it a mid to 'hot' microphone and should not need much gain on the AI. Much depends however on your expectation. For 'musical' purposes the DAW meters should bumble at around -20dB fs. If you are striving for -6dB ish then yes, you will need to crank the gain but for digital recording you don't usually need to be nearly that hot.

Dave.

Ok, so in the weirdest of developments:
I conducted your tests. Two 30s recordings with no inputs, one with phantom power, one without. Both played back with no whine (and not even that much room noise honestly).

So then I plugged the Samson c01 back into input 1 and recorded with no phantom power. Recording had no whine.

So then I turn on phantom power and record recording a has audio with NO whine - wait, what??

So I perform the tests over again in the exact same order. This time though, as soon as I turn on the phantom power, I get the whine again.

I'm about to go bat-shit crazy here. So does this mean my wire is bad and maybe its just not seated well in the XLR port and I happened to get lucky the first time I plugged in the mic after the no-mic test recordings?

I'd swear I imagined the whole thing, but I have the recording with no high pitched whine on my PC so yeah - it definitely happened :D

As far as the specs on the mic - I'm still such a n00b, none of that makes sense yet - still reading up :) But all that aside, all I know is that I have to max the gain to get a usable signal and I'm not going for ear-splitting or even what I would consider loud. OBS shows that the audio level is hovering around -30db (if I'm reading it right :))

[Sam Spoons]

If you plug the ¼" end of the cable into a single line input on your interface you are feeding an unbalanced stereo signal into a balanced mono input. It's a common and easy mistake to make. When you understand the difference* between balanced and stereo it will be obvious why it doesn't work. I'll try to explain :- the stereo signal has right +ve on the ring and left +ve on the tip with the -ve of both on the sleeve, the balanced connection has +ve on the tip, -ve on the ring and only the ground on the sleeve so if you send R+ve to the tip (+ve) and L+ve to the ring (-ve) of the balanced input you'll hear not right and left added together (which would be great) but the difference between left and right (i.e. L+ve minus R+ve). If what you hear has no bass and no lead vocals that is most likely what is happening.

HTH

What happens if,..
You have nothing plugged into the interface, advance the gain to where you usually have it with phantom power switched on. Record.Then repeat the exercise with P power off.

A 30 second recording each time will be enough. The result should be a noise, hiss at around (total guess) -80dB fs. Most importantly there should be no sign of any whine.

If plugging the mic back in produces the whine again? Well I am sure you are ahead of me!

Just looked up the mic's specifications and find it has a sensitivity of -33dB making it a mid to 'hot' microphone and should not need much gain on the AI. Much depends however on your expectation. For 'musical' purposes the DAW meters should bumble at around -20dB fs. If you are striving for -6dB ish then yes, you will need to crank the gain but for digital recording you don't usually need to be nearly that hot.

Dave.

Ok, so in the weirdest of developments:
I conducted your tests. Two 30s recordings with no inputs, one with phantom power, one without. Both played back with no whine (and not even that much room noise honestly).

So then I plugged the Samson c01 back into input 1 and recorded with no phantom power. Recording had no whine.

So then I turn on phantom power and record recording a has audio with NO whine - wait, what??

So I perform the tests over again in the exact same order. This time though, as soon as I turn on the phantom power, I get the whine again.

I'm about to go bat-shit crazy here. So does this mean my wire is bad and maybe its just not seated well in the XLR port and I happened to get lucky the first time I plugged in the mic after the no-mic test recordings?

I'd swear I imagined the whole thing, but I have the recording with no high pitched whine on my PC so yeah - it definitely happened :D

As far as the specs on the mic - I'm still such a n00b, none of that makes sense yet - still reading up :) But all that aside, all I know is that I have to max the gain to get a usable signal and I'm not going for ear-splitting or even what I would consider loud. OBS shows that the audio level is hovering around -30db (if I'm reading it right :))

If you have no mic plugged in there can't be any 'room noise' at all?

* Forgive me if you do understand this and that is not what is happening but this is a forum and sometimes words are not the easiest means of communication...

[chanyam]

* Forgive me if you do understand this and that is not what is happening but this is a forum and sometimes words are not the easiest means of communication...

Nope, you're right - no audio at all. Sorry, I'm in the middle of my work day so I'm posting these somewhat distracted as I try to be "productive" at my day job :)

Thanks for the explaination!

[Sam Spoons]

Hope it helped, get back to us when you can.

[chanyam]

I'm at a loss for how I got that one good recording with no whine. I've tried plugging into a different USB port on the PC, I've tried plugging and unplugging the mic multiple times, I've tried doing so before and after enabling phantom power. And I also went through the tests again (2 recordings with no mic, one with P power, one without and then mic with no P power and then mic with P power). Consistently getting the whine again.

Maybe I should just record myself on my smart phone! LOL :headbang: