I’ve never used a compressor as I’ve pretty much only used Audacity for recording off of the radio up to this point, and as I understand things that signal is already compressed… But I’m toying with the idea of trying my hand at doing audio books and have read a little about it. That probably means I only know enough to make me dangerous.
In the meantime I’m planning on recording a talk at our Church this evening using their mixer/sound system via the “tape out” RCA jacks to my computer & little Behringer UCA 202 interface. I’ve never tried it before, but it works fine taking it from my stereo in that way.
I’d like to hook it up, maybe do a little sound test to make sure it’s set up ok and then go back & take a seat for the talk, leaving my laptop by the sound system to record it all.
The issue, though, is whether I’d need to be there to adjust the mic levels to make sure it isn’t clipping. There will also be a pianist/vocalist & a guitarist/vocalist providing music to start and end the talk.
I’m thinking that perhaps I could set up one of the compression plug-ins or built-ins that come with Audacity that would allow me to set it for the main mic but keep it from clipping if the vocalists have a significantly higher sound level.
That won’t work. To use a compressor / limiter in that way requires a hardware compressor / limiter so that you can control the level before it gets to the UCA 202. If you overload the UCA 202, then the damage is done and no amount of compressing/limiting by software after the event will help.
The way that you handle this will be very hit or miss the first time (so expect the first recording to be rubbish )
Ideally what you would do would be to sound check the main speaker and the pianist/vocalist and the guitarist/vocalist, and anyone / anything else that will be in the recording, and set the levels from the mixer so that whatever is the loudest registers a maximum peak level of around -6 dB in Audacity. I’m guessing that you won’t be able to do that, so you will need to guess at the levels. Make your guess on the low side.
If they all use the same mic and you have chance for a sound check with that mic, get someone with a loud voice to use the mic (loudly) while you set the levels - aim on the low side. If the recording is too quiet then you will be able to amplify it after the event - that will probably make it a bit “hissy” but perhaps still usable. If you set the levels too high then it will clip (distort) and no way of fixing it.
Make a note of what levels you set. If you find that the peak recording level for the loudest part of the show was say -12 dB, then you will know for next time to increase the level by +6 dB.
Is “the damage done” to the recording or to the UCA 202 &/or sound card or to the computer?
Bummer. But that’s good to know going in.
That’s another good thing to know. I was hoping to just be able to plug in and adjust things in Audacity without having to bother any of the settings that the choir uses. Someone there is usually the one that adjusts all of the settings. I got the permission of the Pastor to do the recording. They might not take too kindly to me playing around with those things.
But if the settings at the pre-amp/mixer were turned down a little, I suppose they could still get the same volume by turning up the amplifier a bit?
If the levels being too high only damaged the recording and not any of my hardware, I could probably just plug it in and see if I get a decent signal at their current settings, no? If it’s too low I would just have a weaker signal than would be optimal.
By the way, would it be unusual for them to have it set at good levels for their purposes, which undoubtedly would mean no clipping, but still have too hot of a signal at the “tape out” monitor?
For what it’s worth, the speaker last night did have a few 'plosives. He is on a different mic than the two choir members were using. Each had their own. Later on the speaker also walked away from the podium and was going to use a wireless mic, but it wasn’t working last night for some reason. That would have been the 4th mic they would have used had it worked.
When I’ve recorded off of my inexpensive home stereo via the tape out jacks I’ve adjusted the sound levels via a mic slider in Audacity. I suppose it never sends an unusable clipped signal is because the stereo is set up that way? I don’t think the volume control has any effect on the tape out signal.
Decibels are a measure of how loud a signal is, correct? Why do some measures use negative numbers?
The digital system all uses negative numbers. Zero is maximum volume. That’s where the digital system runs out of numbers and starts to distort because it can’t follow the performance. -60dB is So Quiet you can hear a Pin Drop.
You can use relative numbers. This sound is six dB higher than that.
The Audacity sound meters are 0 on the right and they go to negative numbers on the left as the sound gets quieter.
You have Strike One and Strike Two. You have a wild feed from an unknown performance. Good sound people will be able to make that work. But you’re not going to be there. So chances of success are almost zero.
But not quite. Do you know how to drive the main sound mixer? Does it have a tone generator? Run the generator and set the tone for "0"VU on the main mixer meters. Run Audacity connected to the back of the mixer as you said and set it for -6dB.
Is somebody going to be there to start it? Audacity has a Timer tool and you can force it to start and stop recording at certain times, but it won’t start the computer.
This would be a good time to deputize an assistant to be there rather than trying to fly all this blind.
The UCA 202 is a great little gadget, and very inexpensive, but one limitation that it has is that there is no control of the input level - that has to be controlled by whatever is supplying the signal (in your case it’s the mixing desk). If the sound man (or woman) is not you, then make friends with them asap - find out if they like chocolate - you will need to work with them. Depending on the type of mixing desk, there is likely to be some control of the output level to your UCA 202 that can be adjusted independently of the main output - you will probably need the person running the desk to adjust their “send level” so that your input levels are right.
Decibels are not “units”, they are “ratios”. Decibels are used to compare one level with another. When saying that a signal is so many dB, for that to make sense it must be so many dB relative to a known level. For signals the “known level” is usually “full scale” (maximum valid signal). That means that a “maximum” signal is the zero point (0dB) and all other valid signals are negative (less than zero). This is different from measuring acoustic sound level (“Sound Pressure Level” or “SPL”) - in this case, the reference point (0 dB) is usually taken to be the quietest thing that can almost be heard (the threshold of hearing). Thus for SPL, any sound that can be heard is positive dB.
Thank you. That does help explain things a bit. I see from Steve’s reply below, that there’s an alternate dB usage coming from the other direction, where zero is below our ability to hear it. That’s why I got confused on this. I’m contemplating trying my hand at narrating audio books and was confused when tryiig to compare noise levels for pre-amps from XLR to USB. I had no idea what the noise numbers signified. Was EIN of -125 dB for the Focusrite Scarflet Solo good or bad, and was -125 better or worse than -140. Now I know. Thanks again.
Well, you’re right that I’m not there as a sound engineer. I inherited the job of running the mixer board for the grade school when the real expert who had run sound systems for bands ended up moving away and the lady running the dance assembly thought I must be an expert. That was based solely upon the fact that I had been able to delete an inappropriate section of a song for her via Audacity when one of my kids volunteered that I could do that.
The former guru showed me the basics of turning on the system and how the channels were laid out and which sliders affected which channels. Fortunately the job was pretty simple. I set up the system the evening before the Dance Assembly in the gym… rolling out the main mixer or whatever it’s called, putting out the speakers, hooking them all together, setting the sound levels by ear and making sure everything worked. From my standpoint, it wasn’t much more than setting up a giant sized stereo system, which was pretty much my “expertise” coming in.
My job during the Dance Assembly was to tweak the sound levels for her mic and the CD players by ear, and then to switch the CDs in & out as she signaled. I never really played with any of the dials for the equalizer or anything that would take any technical know how or expertise.
Yes, I’ve used that feature a number of times and love it. That was a big reason I got the Behringer UCA202. I was able to record my school’s basketball or football games that I otherwise would have missed. I had been able to do so without the Behringer before they cracked down on stations streaming the games.
In this particular case I was able to be there for the start and things might have actually worked out had it not been for the fact that it was an even more complicated system than I realized. There were at least two mixer boards, perhaps three.
Well, you were right Steve, the 1st try did pretty much turn out to be garbage. Well, it was just the speaker’s talk that turned out to be garbage, the choir’s songs to start and end the night turned out pretty well.
I was hoping to get there a little earlier, but arrived about 20 minutes before it was to start. The pastor was talking to the speaker right by the mixer board and introduced us saying that I’d be trying to record the talk. The speaker graciously consented to the recording. The lady in charge of the music & choir etc. wasn’t there again tonight and neither her substitute nor the other choir members objected to me hooking my computer up, particularly since I obviously had the pastor’s blessing, so things were looking good at that point.
There was an organ with a flat top right next to & behind the mixer board which was a perfect place to set the computer.
Things went downhill quickly from there, however. It had been awhile since I had hooked up the Behringer to my home stereo, but was pretty confident that I needed to hook up the RCA cable from the “input” jacks on the Behringer to the “tape out” jacks on the mixer board. I wasn’t so confident, however, when things didn’t work as I had expected right off the bat.
I had closed all other programs but Audacity before I left home and it popped right back to where I left off after I logged in when I got there. There were some people already coming in, but I went ahead and hit the record button to try a sound check, but the cursor wouldn’t move from the start position, though it acted like it wanted to, but was being held back. I have had that problem in the past and ended up switching the options around on the drop down menus on the tool bar. It had been working fine on the stereo at home using WASAPI & USB speakers & USB mic, but I started selecting various other combinations and permutations but nothing worked. I tried Windows Direct & MME, for instance, but they would take away the USB mic option & Stereo Mix & Primary Sound Capture Drive would allow the recording to seem to start but were pulling up silence when I’d run up & do a test on the mic that would be used. The pastor went up and started doing mic tests for me so I wouldn’t have to run back and forth, but still to no avail. WASAPI & USB mic continued to not even pretend to try and record for whatever reason.
I don’t remember the details of which selections were selected at the time, but at some point the sound level meters were acting like they were getting signals, but nothing was showing up in the sound waves portion.
I told the pastor to just go ahead and start & I’d fiddle with it as we went. I said a little prayer right then and then they started. To my amazement, so did Audacity as the choir started singing. It was in Wasapi & USB mic and the sound waves were just about right. I was caught a little off guard, but pulled the sliders down on the mic in Audacity a bit but it was actually better where it started, probably just above -6 dB.
But when the speaker started the sound levels dropped way down, almost to the zero line on the wave form & I was almost maxed out on the mic level already. Maxing it didn’t help much. I was wondering if it was just picking up from the laptop mic, or maybe the pianist’s mic, which she had moved out of the way, pointing away from the speaker. I moved the slider up on the mixer board for the channel I had plugged into, but it sounded to me like I had turned up the mic the speaker was using. It sounded a bit loud to me and made a comment about people thinking he spoke too softly. The slider was only about a quarter of the way up, though, and I couldn’t figure out why he would be coming through so loud & clear but my recording was so weak.
There were a couple of other wires plugged into the jacks below mine on that same channel & after I sat down I wondered if the tape in & tape out jacks were on the same channel being used by the speaker’s microphone. I wouldn’t have expected that to be possible, but it had me a little worried.
He was an experienced speaker, but from some recent readings I wondered whether he knew how to “work the mic”. He was having issues with 'plosives and also with the proximity effect to an extent, being a bit too quiet at times and too loud for awhile at other times. That made it hard for me to tell if my slider adjustment had made his mic a little too loud. In any event, it made me too nervous to try and turn it up any & in fact I turned it down a little bit a couple of times to see if it would make his mic a little less loud. I didn’t want to make any changes too obvious, though, as I may have already been distracting people.
I hadn’t plugged in my laptop either as it should run for at least 3 hours, but the screen dimmed and later turned off for power saving mode. I got nervous, though, when one of the power lights went off. I was afraid if it went into hibernation or whatever Audacity would stop and I hadn’t saved the file at all, because I had turned Audacity on and off several times & even rebooted the computer once because I couldn’t get it to go in WASAPI & USB mic mode. I didn’t want to lose everything.
I snuck up & got the charger out of my bag & hooked it up as unobtrusively as I could & luckily it was still recording, though still at the barely audible range.
At the end, when the choir sang it popped right back into the near perfect range.
Afterwards I asked one of the choir members if there were any other mixer boards than this one. I couldn’t see any others around, but couldn’t see why one input, that sounded just as loud as the others should be so much queiter on the tape out monitor. He said that there was an add on board on the other side of the mixer. I went over there and sure enough, there was another board attached on the side and a little lower than the main board. I about kicked myself, saying that had I known I should have plugged into the tape monitor out on that board. He said that actually, those were for some other mics just in front of us that weren’t in use that night since they didn’t have the full choir.
I mentioned how baffling this was to me and then he said that actually these two mixer boards and the mics up on the altar and the cordless mics all fed into a bigger unit in the back in a big closet. I said I should have been hooked into that one then, but they told me that closet was usually locked and no one could go back there. They said it was open tonight however & the guy took me back and showed me a great big metal unit. I’m guessing it was about 4 1/2 feet high, maybe 4 feet deep and about as wide as the mixer boards, maybe a little more. The front was locked in by a heavy metal cage. He opened it for me, but it looked more like some big amps atop one another in a big rack mount. I didn’t get a good look at it, but I saw a few lights maybe but no input our output jacks or anything. The sides wouldn’t open, but he opened the back and said there was nothing in there that looked like I could hook into it. I couldn’t see it from my angle, but was guessing that it was mostly wires connecting them all together but not a standard consumer grade inputs & outputs.
I’m not sure what to make of it all, or if I could figure out how to record it tomorrow evening.
Good. I thought I read something yesterday that warned about damaging the sound card or even the hard drive on a computer due to clipping. That kind of shocked me as I didn’t think that was even a possibility. I hope not. Maybe I read it wrong.
The UCA 202 is a great little gadget, and very inexpensive, but one limitation that it has is that there is no control of the input level - that has to be controlled by whatever is supplying the signal (in your case it’s the mixing desk). If the sound man (or woman) is not you, then make friends with them asap - find out if they like chocolate - you will need to work with them. Depending on the type of mixing desk, there is likely to be some control of the output level to your UCA 202 that can be adjusted independently of the main output - you will probably need the person running the desk to adjust their “send level” so that your input levels are right.[/quote]
Well I get to run a different sound board for the school’s Dance Assembly on Friday morning and will set it up tomorrow night. Hopefully I’ll get a chance to play around with it a bit and try to figure things out.
Decibels are not “units”, they are “ratios”. Decibels are used to compare one level with another. When saying that a signal is so many dB, for that to make sense it must be so many dB relative to a known level. For signals the “known level” is usually “full scale” (maximum valid signal). That means that a “maximum” signal is the zero point (0dB) and all other valid signals are negative (less than zero). This is different from measuring acoustic sound level (“Sound Pressure Level” or “SPL”) - in this case, the reference point (0 dB) is usually taken to be the quietest thing that can almost be heard (the threshold of hearing). Thus for SPL, any sound that can be heard is positive dB.[/quote]
That’s definitely where I was getting mixed up. Years ago I must have read the SPL version and though a decible had been defined as the lowest unit of sound someone with good hearing could actually hear. If I recall they also said that for people to be able to distinguish that one sound was louder than another required a 3 decible increase, and that for each 3 decible increase a doubling of the power was required. I think it was in the context of speakers and amplifiers. Doing the math on how powerful amps would have to be to get to 110 decibles if the speakers could put out 80 decibles at 1 watt of power (just making numbers up here) was pretty eye opening.
Anyway, thanks for all of the help and info everybody. This sound stuff is a lot more complicated (& interesting) than it looks at first glance.
Audacity will sit and wait for a performance if Sound Activated Recording is selected.
Audacity > Edit > Preferences > Recording: [_] Sound Activated Recording (deselect).
If different microphone groups are handled by different mixers, you may never get there with a single UCA202 unless your goal is to record just one portion of the performance. This is a nightmare sound shoot for a pro recordist, so if you have to do this repeatedly, it may take several passes before you get all the ducks in a row.
I have seen that, but have never used that option, and it isn’t checked now.
I’m thinking it just may take my computer awhile to warm up & start recognizing all of the hardware and drivers and things. It has happened a couple of times to me that I just can’t get it to work and try all of the options multiple times and then suddenly it will work like a charm.
Yeah, I would just record the main speaker if I knew how to connect to the correct mixer board, assuming it had a tape out or similar RCA interface I could tap into and could also get access to that mixer board. That doesn’t appear likely, though.
I think I may try to use one of the spare mics on the add on mixer board attached to the one I used last night and aim it at one of the audience speakers and record it that way. If I disconnect the output from that board from the main board that the choir is using, I’m assuming it wouldn’t cause feedback issues. It wouldn’t be the ideal way to record but it might be passable, and probably better than someone trying to get it via an iPhone or something similar.
I’ll have to try and get there a little earlier this evening and experiment with it a bit.
If I were in your position I would ask the pastor if there was some time (maybe a Saturday morning?) when I could have access to the system and spend some time studying exactly what is connected where. With a bit of luck the important stuff will be labeled. The solution to what you are trying to do might be as simple as plugging into the tape-out connections on that second mixer board or it might be a lot more complicated. The stuff in the closet sounds like it is just the Power Amps that actually drive the speakers (and possibly some active crossovers) so with a bit of luck that equipment is not of your concern. Post some pictures of the gear and we can tell you more. Take pictures and make notes of the position of all of the controls on the mixer and then go find the user’s manual for it online and do some studying.
Many boards can provide an Auxiliary output that has its own mix so you might look for such a feature.
With the UCA-202 there is no reason to ever set the “microphone volume” slider in Audacity to anything other than 100%. As others have mentioned that unit does not have any volume control ahead of the A/D conversion, and if you are clipping it’s input, that will continue regardless of the setting of the volume in software.
I have seen Audacity get confused if the UCA-202 is unplugged and plugged back in while Audacity is running. Sometimes (even often) it works but sometimes it doesn’t. I would recommend when setting up don’t run Audacity until you have plugged in the UCA and Windows has had a chance to acknowledge its existence.
Yeah, I was hoping that that big box in the closet was just some amplifiers & things. If there’s another mixer box, it may be elsewhere. I was wishing I hadn’t forgotten my phone at home or I would have taken a few pictures.
Tonight will be the last night for the parish mission, but taking some time talking over how the system is set up with someone who knows more about it would probably still be a good idea. Our pastor seemed happy that I was trying it. He said that they had anticipated recording homilies & things but had never gotten around to it. I’m guessing no one had the equipment or software to do it. I was pleasantly surprised at the quality of the recording of the choir, after I had adjusted the sound levels a bit.
Many boards can provide an Auxiliary output that has its own mix so you might look for such a feature.
With the UCA-202 there is no reason to ever set the “microphone volume” slider in Audacity to anything other than 100%. As others have mentioned that unit does not have any volume control ahead of the A/D conversion, and if you are clipping it’s input, that will continue regardless of the setting of the volume in software.
The UCA202 may not be able to adjust the sound levels coming in, but Audacity can definitely control them once they arrive. If it was clipped that obviously wouldn’t be adequate to save the recording, but wouldn’t the sound boards either have the volumes for tape out or aux out or whatever already adjusted such that there would be no clipping? Would they perhaps have compressors &/or brick walls to stop that sort of catastrophe? I’m guessing that those types of outputs were designed for people hooking a cassette recorder up to it to record the output. Those probably don’t have any hardware based compressors or brick walls I wouldn’t think.
As a side note, what is the main purpose of the brick wall in software plug-ins if it isn’t to prevent clipping? But if I understand the conversation correctly, it sounds like the software would seldom prevent it. If the upstream sound chain had built in compression/brick walls the software wouldn’t need to do it, but if that sound chain did not have that feature built in and clipped it before it ever got to the software, the software would be useless in fixing it anyway. Or am I misunderstanding how it all works?
I have seen Audacity get confused if the UCA-202 is unplugged and plugged back in while Audacity is running. Sometimes (even often) it works but sometimes it doesn’t. I would recommend when setting up don’t run Audacity until you have plugged in the UCA and Windows has had a chance to acknowledge its existence.
Yeah, that’s probably what messed me up. I’ll have to be a little more careful in that regard.
Audacity is a post-production editor. All the tools work after the performance is done and everybody goes home. There’s no shortage of people that want Audacity to filter and correct live performances. Not so far. It’s up to you to get the performance converted to digital with no damage. We got it from there.
and I for one appreciate the job Audacity can do in post-production, even though I’m sure I only know how to use a tiny fraction of its capabilities. I this particular case, Audacity was able to salvage the talk even though I had doubts we could get anything out of it other than the choir’s small parts at the beginning & end. It must have been a little stronger signal than I expected. I amplified it using the default setting & that improved it.
Then I compressed the whole thing, which improved the talk even more. I don’t know if it helped or hurt the choir portions, though, but it did even out the levels between them. Should I have compressed first & then amplified, or is that a case by case decision?
I was surprised that it came out as well as it did considering the circumstances.
Our Pastor was pleased that he was at least intelligible despite the room echoiness and the significant amplification that was needed.
I’m still not quite clear as to the post production brick wall software, however. It sounds like the hard brick wall limiter is most appropriate further down (or would that be up?) the sound chain… before it gets to the recording.
Yes, but it’s better to do any controlling after you make the recording. The volume slider next to the microphone in Audacity is just a multiply on the 16-bits coming from the A/D converter making another 16-bit number. All turning it down on record accomplishes is reducing your signal to noise ratio.
Attached is a sample recording made with my UCA-202 attached to a signal generator. The recording is in two parts, (the division being a bit past 00:05.7) in each part I cranked the signal generator up past the UCA-202’s input clipping level. In the first part the software microphone volume was set to 1.00, and in the second the software volume was set to 0.3. Note that in both sections the waveform goes into clipping (the rounded peaks of the waveform go flat) at the same analog input level. The only difference is that in the second recording those peaks are are 0.3 instead of 1.0. That analog level was just a bit more than 3 Volts peak-to-peak on my unit.
Yes most mixers will have a gain control for their tape or auxiliary outputs, and ideally you get that adjusted such that the loudest program can’t clip the UCA-202. If the mixer has a signal generator and meters then you can use that to set the level. I would recommend that 0 on the mixer be set to about -6 to -10 dB on the UCA. (If the amps in the hall have been properly set up then they will probably have a similar amount of headroom).
I would stop using the English words “Brick Wall.” That effect is used in Air Traffic Controllers and Taxi Dispatchers, both of which have very tight limits on their radio channels. Singing into one would not be desirable except as a comedy effect.
I played the wave file back and could hear the drop in volume, of course, but I wouldn’t have been able to tell that it was clipping had you not told me. The second time I recorded it in Audacity and what you were saying was very obvious.
But that doesn’t mean that I should have the volume slider maxed out on Audacity all the time, right? That just applies to recordings with the UCA-202? I’ve always assumed that I needed to pull that volume slider down when a signal was getting close to clipping, such as when recording a stream via stereo mix.
Yes most mixers will have a gain control for their tape or auxiliary outputs, and ideally you get that adjusted such that the loudest program can’t clip the UCA-202. If the mixer has a signal generator and meters then you can use that to set the level. I would recommend that 0 on the mixer be set to about -6 to -10 dB on the UCA. (If the amps in the hall have been properly set up then they will probably have a similar amount of headroom).
I’ve seen the meters, before, but never knew anything about signal generators, nor even that they were on mixer boards, much less how to use them. That’s obviously something pretty important for something like this. I obviously have some learning to do. Thank you for pointing it out.
OK, are there better ways of describing a compressor that won’t let you clip the signal? It sounds like this moses guy is saying pretty much the same thing, though I’m not sure the term, “a very clever moving gum wall” would catch on:
Waves L series. Hard to beat them.
No piece of gear with the label “compressor” on it has a “brick-wall” gain behavior. Only specialized limiting compressors with zero or less attack time and an infinite ratio have a characteristic which could be (very roughly) described as a brick-wall. Obvious, they wouldn’t be able to do their job if they weren’t “brick wall”. So, it might be helpful to ask for the best limiter instead. I suppose that’s what you are searching for.
In any way, the term “Brick-Wall” is marketing motivated and not very intelligent from a scientific point of view.
In fact, the analogy is wrong with common limiters and compressors. The “brick-wall” basically describes clipping, which is instant, state-less compression - basically the opposite philosophy of how compressors and limiters are built (in which the gain reduction is smoothed out to not act like a brick wall).
So a good analogy for a compressor/limiter might better be a very clever moving gum wall. At least, it’s much better describing the process.
Yes, probably not just the UCA-202 as there are lots of other A/D interfaces with the same issue. But there is gear out there where the little volume slider actually controls an analog attenuator ahead of the A/D conversion, so for that gear then using the slider to adjust the levels is a sensible thing. And unfortunately the only way to find out what a particular bit of gear does is to test it.
Yes that’s true in general, but you need a slider that acts upon the signal before it is digitized. If I had my way the Behringer interface wouldn’t pretend that it had a level control, but I’m guessing that may not have been an option for them – windows may require a control – so they did what they could.
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