Mystery of the tiny waveform and intermittent 1000 hz tone

[skboren]

I’m a novice, using Audacity for a project for my kids’ homeschool group. Please forgive my ignorance. I have a studio mic with an XLR connector (this one: http://www.pyleaudio.com/sku/pdmic58/professional-moving-coil-dynamic-handheld-microphone).

I have an adapter to make the mic work with the computer (see photo). I have it plugged into the mic input port on the back of the CPU. When recording, we get a tiny waveform, despite input slider dragged all the way up and despite our being plenty close to the mic. We also get a 1000 hz digital-sounding tone in the background of the recording, which of course only gets louder when we run “normalize” in order to help amplify the tiny waveform. The 1000 hz tone only occurs when I use this mic. If I use our webcam mic or the default computer one, the sound quality is poorer but there is no high-pitched tone.


I read about how if you plug a mic with an XLR connector into the line input on your computer, you can have problems with the sound (http://manual.audacityteam.org/o/man/tutorial_connecting_a_microphone.html). But I’m plugged into the mic port, not the line input.

I’m wondering whether some smart person can tell me why I might be getting such a tiny waveform, and why we might be getting that 1000 hz tone. I’ve attached a piece of the audio.

Thanks much in advance!

Shauna

[DVDdoug]

I read about how if you plug a mic with an XLR connector into the line input on your computer, you can have problems with the sound (> http://manual.audacityteam.org/o/man/tu > … phone.html). But I’m plugged into the mic port, not the line input.

A pro mic mic input doesn’t work properly with a soundcard either. Good mics are low-impedance balanced (3-wires). Computer mics are high impedance unbalanced (2-wires). That accounts for the low signal.

Additionally, the mic preamps on consumer soundcards tend to be low quality. That probably accounts for the ~1khz noise.

A XLR to USB “adapter” like [u]this[/u] will bypass your soundcard and should give you very good results. You can get all kinds of XLR-USB audio interfaces from places like [u]Musician’s Friend[/u]. These are what pros use in place of a regular soundcard. Another alternative is a “studio style” USB microphone.

A transformer like [u]this[/u] will “match” the impedance, convert balanced to unbalanced, and boost the voltage level. But, it won’t do anything about the preamp built into your soundcard. (Except the higher signal will give you a better signal-to-noise ratio.) You’ll also need the 1/4" to 3.5mm adapter which I think you already have.

[skboren]

DVDdoug, thank you!

So it sounds like the XLR to USB adapter is a better solution than the transformer. Is that right?

Would this cable serve the same purpose and bypass the soundcard? http://www.amazon.com/gp/product/B00B6WZGHS/

Thanks, again.

Shauna

[skboren]

So, I bought the Griffin iMic, and it neither boosted the signal nor eliminated the high pitched tone. The recording quality is exactly the same. Do I need the tranformer to match the impedance, too? I was thinking I only needed one or the other, but maybe I need both?

Thanks!
Shauna

[steve]

Your “PylePro PDMIC58” microphone is a copy of a “Shure SM58” mic.

As written previously, these types of microphone (and almost all professional microphones) are designed for plugging into a “balanced XLR connection with around 600 Ohm input impedance”.

These types of microphones are also designed to be used close up (think of a rock singer “eating” the microphone).
Recording at distance is difficult because the sound level drops off rapidly as you move away from the sound source. If you sing directly into the microphone (with the mic just a few inches away from your mouth) and adjust the recording levels accordingly, I would expect that most of the problems will disappear.

[Gale_Andrews]

Additional to Steve’s point about getting close to the mic…

@skboren

So, I bought the Griffin iMic, and it neither boosted the signal nor eliminated the high pitched tone. The recording quality is exactly the same. Do I need the tranformer to match the impedance, too? I was thinking I only needed one or the other, but maybe I need both?

Presumably you are plugging the same 1/4 inch to 1/8 inch adaptor into the iMic, and that is the cause of the problem. You’ve bypassed the built-in sound card but not bypassed the impedance mismatch.

If you have iMic set to line, you could try setting it to mic, which will boost the level. Have you tried adjusting the volume slider for iMic in the recording side of the Windows control panel for sound?

Increasing the input level may push the whine sufficiently into the background for you, or it may not. If not, you should try the transformer Doug mentioned, which you can put between your mic and your 1/4 inch to 1/8 inch adaptor, plugged into iMic as now.


Gale

[skboren]

Thanks for the replies.

Getting very close to the mic does help the signal (-0.5 to 0.5), but the whine is still very audible.

The slider for mic recording volume in Windows Control Panel is at max already.

If the output impedance is 600 Ohm on the mic, will the transformer (http://www.amazon.com/Hosa-Technology-MIT-435-Signal-Converter/dp/B000068O68/) which is “designed to match 200R output impedance to 50K input impedance” still be effective to reduce the whine? Or should I try to find a transformer that matches 600 Ohm to 50K Ohm?

Thanks,
Shauna

[steve]

@skboren

Getting very close to the mic does help the signal (-0.5 to 0.5), but the whine is still very audible.

The slider for mic recording volume in Windows Control Panel is at max already.

Are you this close?
(that’s a “Shure SM58” microphone)

[skboren]

Yes, I’m about as close as I can be. Mind you, on the recording attached to the original post we are not so close. But at the distance shown in the photo, we can get a waveform ranging from -0.5 to 0.5. But no bigger, and the whine is still there. Thanks.

[steve]

OK, so now for further improvement we need to look again at what you are plugging the mic into.

You will notice that the connector on the microphone has three prongs. All three should be used.
You will notice that the jack plug on the end of the lead (and the adaptor) have two connections (“tip” and “sleeve”).
So how have they connected 3 contacts on one end of the lead to 2 contacts on the other? The short answer is that it is a cost cutting exercise that shouldn’t be done.

The three connectors on the microphone each do separate jobs. Two of them form the signal circuit, and the other one shields against electrical interference. A three-into-2 lead will mostly work, but it joins one of the signal leads to the shield lead, which compromises the effectiveness of the shielding. The only real solution to that is to use a proper XLR lead (3 pins on one end and three holes on the other - male XLR to female XLR) and plug the mic into a proper XLR microphone socket.

The cheapest way to do that is to use one of those USB microphone cables, but from the reviews that I’ve read I wouldn’t recommend them. A better, but sadly more costly solution is to use either a USB mixing desk or a USB microphone pre-amp. At this point we need to ask what you are wanting to do with the equipment and a rough idea of your budget.

[skboren]

Steve, I soooo appreciate the thorough and very helpful replies.

If truly the only way to get rid of the high-pitched whine is to buy a USB mixing desk or a USB microphone pre-amp, then that’s the territory I’d like to traverse. If there is any such thing as a cheap transformer that will convert the mic’s 600 Ohm output into whatever what the computer needs to match impedance (here showing my ignorance of terminology and technical specifics again), then I’d like to go the cheaper route.

So I guess what I am asking is, do we think the high-pitched whine is due to an impedance mismatch between the microphone output and what is required by the computer? Or do we think the whine is due to interference caused by the 3-into-2 lead?

At this point all we’re needing to do is a minor project for friends and family, but I anticipate us doing more recordings for any number of purposes in the future, so I would love to get the proper equipment to get a clean signal. Just haven’t had time to learn what else I need.

Thanks!!

Shauna

[Gale_Andrews]

If you’re really worried about getting the correct impedance matching then you would need the Shure X2u which must be matched by definition (but for that price you could get an entry level USB interface with two - possibly not highest quality - XLR inputs).

The Blue Icicle should work well enough too (possibly with a little more noise). See this comparison of X2u and Icicle connected to Shure SM57 which is basically the same as SM58.

Obviously you could try the transformer Doug mentioned on the basis you have not lost much money and it’s better than the USB cables that probably don’t do any matching.


Gale

[steve]

Different options have different limitations.

XLR to USB converters are a cheap option, but usually offer no analog amplification of the (tiny) microphone signal prior to converting to digital, so low signal level and high noise are common problems. You can generally only use one USB audio device at a time with Audacity.

“USB microphones” can offer good recording quality, but you can’t get far away from the computer (hence picking up noise from the computer fans etc) and generally you can only use one USB audio device (microphone) at a time with Audacity.

The Shure X2u, Blue Icicle (and others) are similar to the “snake” type XLR to USB converters, but usually much better quality in both build and sound, and usually have a built-in analog microphone pre-amp. The pre-amp allows the microphone signal to be amplified to a suitable level before being converted to digital. Generally you can only use one USB audio device (microphone) at a time with Audacity. Note that the Shure X2u is built to professional standards, so it’s a world apart from a $10 “snake” USB adaptor.

USB microphone pre-amps (such as “ART USB Dual Pre” and similar) often have two inputs. This allows you to record two separate microphones at the same time (can also be used with one microphone). The recording of two mics appears in Audacity as a stereo track, which you can then either use as a single stereo track, or split into two mono tracks (very useful for recording two voices at the same time). This is often an excellent choice if you are on a tight budget as it can provide good quality recording, quite a lot of flexibility, and can be “upgraded” at a later date by buying a second microphone or upgrading your microphone(s).

USB mixer: This has the advantages of a two channel USB microphone, often with the addition of tone controls and additional inputs for more microphones or other inputs, though usually the number of channels recorded is limited to 2. High end (expensive) USB mixers may provide multiple separate channels to be recorded at the same time, though it may be necessary to use other recording software to make use of this. Note that some of the cheaper USB mixers do not allow you to hear both what you are recording and previously recorded tracks at the same time.

Mixing desk + USB “line level” audio device (such as "Behringer UCA 202 or similar) is probably the most versatile set-up as it gives you all the features of a mixing desk + the convenience of USB audio. Usually this set-up is limited to 1 or two channel recording.

[Gale_Andrews]

I’ll add another limitation of not only USB mixers/interfaces but of all mixers/interfaces - they do not accept USB mics or any other kind of USB inputs. So if you need the mixer/interface, get an XLR mic.


Gale

[kozikowski]

I wonder about that tone, though. That’s not normal. There are “normal” problems that microphones and soundcards have and that isn’t one of them.

I have plugged similar microphones into soundcards very much like you did with the adapters in the top of this thread and mine worked fine after I found the “Microphone Boost” setting. Also called “20dB Boost.” It’s a selector setting for microphones that don’t have a lot of moxie (technical term). It’s usually somewhere in the Windows Sound Control Panels. It may be valuable to look again and see if you can find that setting. That one click could get you out of trouble, at least initially.

http://forums.guru3d.com/showthread.php?t=347233

The Shure SM58 is perfectly willing to produce a very healthy sound signal if you sing loudly into it, impedance match or not. You can connect one to a raw telephone line, scream into it and be heard at the other end miles away. Ask me how I know that.

Koz

[kozikowski]

Your guitar amplifier plug-adapter jams two of the three microphone pins together (one and three) and leaves your voice on one pin (pin 2). What this directly kills is your ability to drag the microphone cable across the parking lot and perform your gig fifty feet from the amplifier. Since most club performers are six feet or less from the amplifier, this isn’t generally a big deal. There are other considerations, but that’s the big one.

So yes, I expected that to work.

You should plug that up again and go looking for that boost setting.

Koz

[Gale_Andrews]

@kozikowski

You should plug that up again and go looking for that boost setting.

Let us know what happens if you turn the mic boost “on”. You may find though that the whine and mic / computer noise will also increase substantially.


Gale

[kozikowski]

You may find though that the whine and mic / computer noise will also increase substantially.

Perfect true, but if the boost happens in the physical preamp ahead of the interference, your problems may go away.

A note on the Shure X2U. I did the product testing and overdubbing certification and I can tell you it does work, but I would not buy another one. It’s about the same price as my small Peavey sound mixer and the Peavey increase in sound quality and versatility is striking. Behringer makes similar small sound mixers and they, too work very well.

I don’t have a good picture of my mixer in action…

http://www.sweetwater.com/store/detail/PV6/
There’s a direct USB version as well. I have not tested that.

If you need a portable microphone system, then the small mixers may not be for you, but remember the X2U can never be more than about 6 feet (2M) away from the computer. That short USB cable can be a harsh master.

Koz

[skboren]

Gale, the link to the comparison of smaller USB audio interfaces is really helpful. It’s nice to be able to hear actual audio samples of the mic-interface combinations. Thanks also for pointing out that we can’t use USB mics with any type of mixer.


Steve, really appreciate the breakdown of choices for purchasing hardware depending on budget and desired outcome. Why is it that the most versatile option (mixing desk + USB “line level” audio device such as "Behringer UCA 202 or similar) is limited to 1-2 channel recording? Is that because it has to go through the Behringer UCA 202? Is that true even if the mixing desk has more than 2 channel capability? I’m pretty excited about this, because if the research I’ve done thus far is accurate, it looks like any of the setups you’ve described can be had for <$200, which is doable for us here. If any of those options can fix the tone/whine issue, I’ll be thrilled.


Koz, thanks for posting about the “Microphone Boost” setting. I did find it after some searching (running Windows 8), and it actually lets us go up to 30db! That improved the signal strength considerably! It creates more noise, too, and makes the whine louder (which is what Gale said it might do) but combining the mic boost with the “Noise Removal” effect, we are getting a much better sound overall than before! “Noise removal” takes care of about 80% of the noise and 50% of the “whine”. Oddly (or maybe not), that boost setting is only an option when we use the mic plugged directly into the CPU mic port. If we go through the Griffin iMic we lose the boost setting, and our signal is much weaker.

I am assuming based on your explanation of how the amp plug-adapter jams two of the three mic pins together, that if we have a male-to-female XLR cord running from the mic to some type of USB audio interface that has XLR imputs, it would eliminate the necessity of the “mic boost” setting. Is that right?

Koz, thanks also for posting the link to the mixer you use. I notice that it doesn’t appear to have a spot for a USB cord, so does that mean that you use something like the Behringer UCA 202 that Steve mentioned, in order to record on the computer? That’s probably a dumb question, thanks for being patient with a novice.


So, thanks to Koz’ suggestion, we are getting a healthy signal. Now my only issue is that I still have the high-pitched whine to contend with, which is louder with the mic boost on, and which is only partially remedied by Audacity’s awesome “Noise Removal” effect. Given that the whine is amplified by the “mic boost” setting in Windows Control Panel, does that help us pin down the source of the whine with any more confidence? I am leaning towards getting a simple mixing desk + Behringer UCA202 Audio Interface as long as we’re pretty sure that’ll fix the “whine”.

I’m also excited to be able to record from multiple mics simultaneously, because we’ve noticed we get a much better sound when recording separate vocal and instrumental tracks on top of one another, rather than recording 3 people on vocals plus a guitar all around a single mic.

Thanks again for all the replies. I’d be grappling in the dark without this forum.

Shauna

[kozikowski]

Where to start.

The three pins on the bottom of the microphone are: 1 - ground or protective shield, 2 - Voice signal, and 3 - Voice Protection signal (that’s the simplified version). If you have a mixing desk that properly uses all three pins, that allows you to place the microphone hundreds of feet away (on the stage) and with reasonable care, produce a show like that. You don’t HAVE to use the protection signal and if you don’t, the only significant problem is distance (again simplified).

(which is what Gale said it might do)

There was always the possibility it was going to do that. It’s impossible to tell where the buzz or whine is coming from.

If we go through the Griffin iMic we lose the boost setting, and our signal is much weaker.

The boost setting is analog, not digital. In the Griffin, all the analog is in the iMic and the computer can’t get to it. Of course, some devices do provide software that helps with this. That’s the driver package that some devices come with.

“Noise removal” takes care of about 80% of the noise and 50% of the “whine”.

It makes my teeth hurt when Noise Removal is required for a show. Noise Removal isn’t “free” and if you’re not careful, you can damage the quality of your voices.

I am assuming based on your explanation of how the amp plug-adapter jams two of the three mic pins together, that if we have a male-to-female XLR cord running from the mic to some type of USB audio interface that has XLR imputs, it would eliminate the necessity of the “mic boost” setting.

Only that the mic boost setting wouldn’t do anything. Again, that only works inside the analog soundcard in the computer. A proper mixing desk or other device may have enough controls and adjustments to make the mic boost unnecessary.

I am leaning towards getting a simple mixing desk + Behringer UCA202 Audio Interface as long as we’re pretty sure that’ll fix the “whine”.

Microphone volume, the size of the signal on pin 2 of the microphone is stunningly small. It’s so small (how small is it) that they warn you when you buy your own soundcard for the computer that you built yourself to plug it in as far as possible away from the video card and other sources of computer electrical noise. They leak into each other through the air and it’s very difficult to build everything so it’s all quiet and well behaved. That’s one reason nobody is throwing any quality awards at sound cards. They live in an insanely hostile environment.

If you have a non-digital mixer like I do (straight PV6), you can use a Behringer UCA202 to connect it to the digital system in your computer.

http://www.kozco.com/tech/audacity/pix/peaveyUCA202Lenovo.jpg

However, that’s not how I did it. I intentionally bought a new but slightly older design Mac that has its own good quality stereo analog audio connections and I don’t need the UCA202. From the mixer straight into the Mac.

The other way to do that is to get a USB mixer. The mixer has the usual audio connections, but it also has a USB digital connection.

http://www.sweetwater.com/store/detail/PV6USB

As an example. Other manufacturer’s make this kind of thing. Also note that you can get these mixers much wider, to 20 inputs or more. Behringer, the maker of the UCA202 makes very nice mixers as well.

Since we don’t know where the whine is coming from, we don’t know where the whine is coming from, to be redundant. Most problems like this are associated directly with the stunningly tiny microphone signal not having enough energy to overwhelm buzzes and whines. If the mixer is providing the boost, then the tiny microphone signal never gets close enough to the computer to cause problems.

Proper mixers have three different ways to control volume:

In my case, the “gain” control up where the microphones plug in (pix 1) is the physical equivalent of the “boost” control. It’s the Goldilocks knob. Adjust or trim the microphone volume so it’s neither too loud of too soft, but juuuuust right. Some mixers call this the Trim control.

The microphone fader below that, the level control (pix 2) controls the volume of each microphone as compared to all the others. This is where you set the theatrical mix. Many mixers have sliders here rather than knobs.

The final place to set volume is the master (pix 3). Many mixers have two sliders here and they’re normally red. This sets the overall volume of the show and is the only place that will allow you to fade the show out at the end.

Between all those adjustments, you can almost always get good volume from a performer.

Note that you still have to have a reasonably quiet room with no echoes, and no matter what we do with technology, we still can’t remove barking dogs in post production.

Koz