Different output levels with the same USB audio interface

D

Daniel Postilnik

Junior
Jan 14, 2011
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San Francisco, CA
I am currently in the process of trying out an external USB interface in an environment where multiple people per day are connecting to the sound system with different laptops. The idea was to eliminate the variable of differently-constructed internal sound cards and standardize the signal level seen by the sound system. I'm currently using the Music Streamer III - http://www.amazon.com/HIGH-RESOLUTION-TECHNOLOGIES-A350-HRT/dp/B00K2436MI

So far it sounds great, but there appear to be differences in output levels between two laptops. If the sound is being sent over USB and computer output controls are disabled, what determines the output level?
 
Re: Different output levels with the same USB audio interface

Daniel Postilnik said:
OS X (various iterations) and iTunes.
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In that case, how do you defeat the audio level controls? There are level controls in the sound control panel, the iTunes window, and the info window of the individual track. AFAIK none of them can be "defeated", all of them effect the output level. There are lots of opportunities for your multiple computers to not match.

Once it comes out of the USB port as 1's and 0's the interface is just turning them into analog audio at whatever level the 1's and 0's tell it to.

Mac
 
Re: Different output levels with the same USB audio interface

mackerr said:
In that case, how do you defeat the audio level controls? There are level controls in the sound control panel, the iTunes window, and the info window of the individual track. AFAIK none of them can be "defeated", all of them effect the output level. There are lots of opportunities for your multiple computers to not match.

Once it comes out of the USB port as 1's and 0's the interface is just turning them into analog audio at whatever level the 1's and 0's tell it to.

Mac
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Agree 100%, and this is why we try to discourage the use of individual presenter's computers. Then the issues become "will machine X play the imbedded video in the power point?" Sometimes seemingly identical machines do not work the same... and we wind up using the presenter's machine because it's the only one in the building that will play the video.
 
Re: Different output levels with the same USB audio interface

More importantly, since it's a USB device, you might on occasion have driver problems. It's unlikely, but I've seen it happen.
 
Re: Different output levels with the same USB audio interface

mackerr said:
In that case, how do you defeat the audio level controls? There are level controls in the sound control panel, the iTunes window, and the info window of the individual track.
Click to expand...

All of that, and are they actually playing the same audio files anyway?

Chris
 
Re: Different output levels with the same USB audio interface

Max Warasila said:
More importantly, since it's a USB device, you might on occasion have driver problems. It's unlikely, but I've seen it happen.
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Have you seen a driver problem that affected the output level? I've seen them do everything from simply not work all the way to causing a BSOD, but never where it worked but was simply quieter.

Chris
 
Re: Different output levels with the same USB audio interface

Chris Nixon said:
All of that, and are they actually playing the same audio files anyway?

Chris
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The goal is not to defeat all volume controls but to remove discrepancies between laptop audio hardware. It's not good for me when users ask me "why does this other person's laptop sound louder?" and I can't answer the question because apple doesn't publish any meaningful specs about their laptops' sound performance.

Also, the USB port in general is used less than the headphone jack in the case of my users, and thus presents a more reliable physical port to use in critical settings. As for BSOD happening, these devices are driverless or they utilize operating system drivers. It makes user setup a breeze.

We have an open architecture DSP to prevent damage to the system and prevent excessive volumes.
 
Re: Different output levels with the same USB audio interface

Daniel Postilnik said:
The goal is not to defeat all volume controls but to remove discrepancies between laptop audio hardware. It's not good for me when users ask me "why does this other person's laptop sound louder?" and I can't answer the question because apple doesn't publish any meaningful specs about their laptops' sound performance.
Click to expand...

Does anyone else?

Also, the USB port in general is used less than the headphone jack in the case of my users, and thus presents a more reliable physical port to use in critical settings. As for BSOD happening, these devices are driverless or they utilize operating system drivers. It makes user setup a breeze.
Click to expand...

In my experience the headphone out is not only less reliable, since it is so easy to bump the cable and cause a dropout, but nowhere near the audio quality. It is true that all the simple USB output devices I have used are driverless, and the same amount of effort to select as the output device as the headphone port.

If there are differences in output level between machines, why isn't the soundman correcting it at the console like he should, or if there is no soundman, why aren't the users adjusting their own computers?

Mac
 
Re: Different output levels with the same USB audio interface

mackerr said:
Does anyone else?



In my experience the headphone out is not only less reliable, since it is so easy to bump the cable and cause a dropout, but nowhere near the audio quality. It is true that all the simple USB output devices I have used are driverless, and the same amount of effort to select as the output device as the headphone port.

If there are differences in output level between machines, why isn't the soundman correcting it at the console like he should, or if there is no soundman, why aren't the users adjusting their own computers?

Mac
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Mac, we're talking about nearly identical sound systems in 32 locations being used all day, every day. I'm the only person responsible for sound for all locations--they are distributed installation systems. When the levels are considered too low for the users when the provided control fixtures are at maximum, they resort to boosting in the iTunes equalizer. This further overdrives the under-spec'd headphone output, leading to distortion. Proper training can curtail this behavior to some extent, but I prefer a technological solution to mitigate the negative effects.
 
Re: Different output levels with the same USB audio interface

Daniel Postilnik said:
Mac, we're talking about nearly identical sound systems in 32 locations being used all day, every day. I'm the only person responsible for sound for all locations--they are distributed installation systems. When the levels are considered too low for the users when the provided control fixtures are at maximum, they resort to boosting in the iTunes equalizer. This further overdrives the under-spec'd headphone output, leading to distortion. Proper training can curtail this behavior to some extent, but I prefer a technological solution to mitigate the negative effects.
Click to expand...

Sounds like you need AGC on your DSP for the laptop input channels.
 
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