Low Recording Levels via USB output from Mixer Board

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Low Recording Levels via USB output from Mixer Board

Permanent link to this post Posted by tbragg » Wed Feb 21, 2018 6:01 pm

Hello, I need to record live sound with Audacity 2.2.2 via a USB output from a new Mackie VLZ2404 mixing board.

I have downloaded drivers for the USB outputs on the board, loaded them onto a Windows 7 Asus laptop.

The laptop sees the board outputs and can input sound to the board via the same USB connection.

Problem: recording levels from the board are very low. I can gain Audacity to maximum recording level and recording levels are still low (less than 50 on the Audacity linear recording scale) and the noise floor is greatly increased.

Mackie tech support states that this is a known issue with Audacity, and suggest that I use an Audacity suite tool - I think it was "gain tool' or similar - to increase the recording levels from the USB input without increasing the noise floor substantially.

Does anyone know anything about this tool in the Audacity suite? I am unable to find either a suite or a gain tool.

Thank you.

Tim
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Re: Low Recording Levels via USB output from Mixer Board

Permanent link to this post Posted by DVDdoug » Wed Feb 21, 2018 7:51 pm

(less than 50 on the Audacity linear recording scale)
50What? -50dB or 50% ?

If it's -50dB something is "seriously wrong". 50% is perfectly OK, and you can use the Amplify effect after recording.

and the noise floor is greatly increased.
When you amplify digitally you boost the signal and noise together, but the signal-to-noise ratio is no worse.* If you've got excessive noise, that's an analog problem.

Mackie tech support states that this is a known issue with Audacity
No... Audacity simply captures what it gets from Windows and the drivers.

There are some optional "Windows enhancements" that can mess-up the sound and if you're at -50dB we can look into that.

and suggest that I use an Audacity suite tool - I think it was "gain tool' or similar
As above, you can use the Amplify effect after recording.

to increase the recording levels from the USB input without increasing the noise floor substantially.
No matter how you amplify the signal from the mixer, you're going to boost the signal and noise together, and the noise becomes more noticeable.


* There is digital quantization noise. Under normal conditions (at 16-bits or better) you can't hear it (and it's way-way below the analog noise) but if you have to boost by 50dB you probably will hear it.
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Re: Low Recording Levels via USB output from Mixer Board

Permanent link to this post Posted by kozikowski » Wed Feb 21, 2018 8:22 pm

That mixer has the ability to switch a number of different busses and configurations out the USB. Are you sending "Main?"

Also from the pictures, they call "0" a good 20dB down from digital overload. Perfectly valid. 20dB headroom for live performances is a good thing. That's zero VU, not zero dB.

However, you should know that their natural peak volume is only going to be 10% or less on the Audacity blue soundwaves. Depending on your screen size, you may not even be able to see that.

You can set your own operating volumes. perform something (tone is good, nobody does that any more), and increase mixer volume until the top red light on the Mackie sound meter lights up. That should be full up on the Audacity sound meters (Green > Yellow > Red) and blue waves that fill the timeline top to bottom.

If that doesn't happen, then we get to find out where the sound is getting lost.

Mackie tech support states that this is a known issue with Audacity


That's a bunch of horse bananas. It can seem that way because Audacity doesn't apply effects or corrections during recording. So whatever the system is feeding, that's what it gets.

Further, it's very common to create USB microphones with low volume. It's easiest to keep new users out of trouble that way, but it appears that Audacity is screwing up.

It's not.

Koz
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Re: Low Recording Levels via USB output from Mixer Board

Permanent link to this post Posted by tbragg » Thu Feb 22, 2018 5:50 am

Hi DVDdoug,

Thank you for your resposne.

As to your question:

50What? -50dB or 50% ?

It is -50db down on Audacity''s recording decibel scale. In my initial post, I mistakenly referred to it as the linear scale.

I have checked to see if there are any Windows settings that could be interfering. Record level in Windows is set to 100%. No effects are in use. Everything there appears normal.

The noise I was hearing could well be the quantization noise you mention. I do have to boost a enormous amount to get proper playback levels from the recording.

I am going to experiment with the amplify effect you mentioned. Perhaps that is what Mackie TS was referring to.

Hi Koz,

I am sending Audacity the 1 and 2 USB outputs from the VLZ 2404 USB output.

You are correct - I am sending 'main' to the laptop. The laptop sees 3 and 4 USB outputs as well and I have tried using them in Audacity as well, but the low levels persist.

I am feeding the VLZ 2404 from the laptop headphone output to a channel pair on the board, and I have also tried feeding it back the the two USB return channels.

Both sound about the same, and levels are correct if I use some other music source on the laptop, such as Windows Media Player, and not anything recorded by Audacity.

It just appears that the volume of sound recorded in Audacity is low, and that issue is not present in any other sound sent to the VLZ 2404 from the laptop.

Regarding the peak volume, your suspicion is correct - the blue sound waves are not even discernible in Audacity as the recording is made.

Just a flat blue line unless I change the meter scale to way smaller than the default.

Thank you for your thoughts.

Tim
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Re: Low Recording Levels via USB output from Mixer Board

Permanent link to this post Posted by kozikowski » Thu Feb 22, 2018 6:13 pm

Still. That's not normal. What are you recording in Audacity? Look at the drop-down next to the microphone, or Audacity > Edit > Preferences > Devices.

We're leery about mixers that offer multiple channels. It's not unusual for them to need special Windows sound drivers to work right.

Problem: recording levels from the board are very low.

What do the meters on the board say? "Woooooof" into a microphone and see where the board's meters go. I expect them to be in the top third.

Did you try the overload test? When everything seems confusing, overload is a good test. Most digital work overloads at the same volume. If you make the mixer's red meter light come on, Audacity should overload as well.

Koz
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Re: Low Recording Levels via USB output from Mixer Board

Permanent link to this post Posted by kozikowski » Thu Feb 22, 2018 6:18 pm

There is another embarrassing error people make. The reason you're recording low volume is you're recording your laptop microphone, not the Mackie.

Again, back to the microphone plugged into the Mackie. Do the scratch test. Do you know where the laptop microphone is? Mine is just left of the left-hand Shift key. Start a recording and scratch each one.

http://kozco.com/tech/audacity/clips/ScratchTest2.mp3

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Re: Low Recording Levels via USB output from Mixer Board

Permanent link to this post Posted by DVDdoug » Thu Feb 22, 2018 7:46 pm

Koz might be onto something with drivers & multitracking, and in fact Audacity may be the wrong software for you... Mackie has an association with Tracktion and some of their products come with that software, but any multitrack DAW application should work.

...Most "USB mixers" only send the 2-channel stereo-mix out the USB bus and they usually work with the regular Microsoft-supplied drivers. Your mixer may be more advanced than that.

I couldn't find VLZ2404 online, but I found 2404VLZ4. Is that it?

I have downloaded drivers for the USB outputs on the board,
Is that the ASIO driver? Audacity doesn't support ASIO.* And, everybody seems to have trouble with multitrack recording.


* Audacity can be compiled with ASIO support, if you're a programmer, but Audacity is not distributed with ASIO for legal/licensing reasons.
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