Noise Floor of PreSonus FireStudio Mobile

A

Adrian Lopez

New member
How much white noise should I expect to hear from a clip recorded using a PreSonus FireStudio Mobile interface, with nothing plugged in, phantom power turned off, and the gain on the mic inputs turned down all the way? I'm getting more noise than I think is normal, but maybe I'm just expecting too much?

I'm attaching an MP3 sound sample so you can listen to what I'm getting. The sample was recorded at 44.1 kHz, 16 bits per sample.

I'd like to know if this is normal and whether or not I should replace the FireStudio with some other interface.
 

Attachments

  • Presonus Noise.mp3
    1.2 MB · Views: 43
Well listening to it, I cannot tell there is no signal on it. I recommend to do a test recording with a music instrument such as an acoustic guitar recording using microphones or acapella vocals then record at 24-bits/48KHz.

Record with peaks mostly at -15dBFS to -6dBFS (watch the recording levels). Then listen to your nearfield monitors and assess whether the noise is degrading the recording. SOmetimes a subjective judgement is important; but if the noise is too significant this is where you will start troubleshooting. IF things are quite, there is nothing to worry about.

Also presonus have its S/N (signal to noise ratio) specs somewhere on the manual. So check on it and you get a rough idea about the acceptable noise in the recording.
 
Here's a quick and dirty recording of an acoustic guitar. Left channel has the mic (at about 1/4 gain; range is -10 to 70 db), right channel is empty (with gain set to -10 db). The room itself is so noisy that I thought posting a sample with no signal would better represent the amount of noise coming from the interface, but hopefully this one will give you a better idea of what I'm hearing.
 

Attachments

  • Guitar.mp3
    453.1 KB · Views: 15
I zoomed in a long way on your first file and your noise floor is sitting at around -60dB. With nothing connected, I'd expect more like -100dB. I just did a test of the crappy built in sound card on my laptop (which I never use for recording...it's too noisy!) and it managed -68dB. You also have quite noticeable DC offset. Neither is in any way normal on a Presonus interface which should be performing way better than that.

As you say, there is a lot of room noise in the second sample so it's hard to judge the Presonus on the one.

I'd say there's a fault with your interface. If it's under warranty, get them to replace it; if it's not then you likely need a new one.
 
I own a Presonus Mobile and I've never had the problem you're describing, so maybe you have a faulty set. Did you get it new or used ? Are you connecting it to a laptop or a computer ? If you're using a laptop and the laptop is charging, that could be the source of the noise. Are you using the external power supply or are you powering it through the firewire cable ?
 
From the Presonus site:

S/N Ratio
(Unity Gain, unwtd, Ref = +4 dBu, 20 Hz to 22 kHz) >101 dB
Click to expand...

Now, considering that this is the spec for a microphone pre amp, it's a bit of a cheek giving a number for a line level source...but I'm sure it's safe to assume that the basic S/N should be a LOT better than those samples.
 
Bobbsy,
I'm getting the same noise on line-level inputs, so I'm guessing the problem is further down the line. Only if I change the routing on either channel so there are no inputs mapped to it do I get no noise on that channel.

saads,
I bought it new from a reputable online retailer. I'm connecting it to my computer (3.20 GHz Intel Core i7, Windows 7) via 6-pin Firewire (TI chipset). I get the same noise whether or not I attach the external power supply.
 
I have the firestudio mobile.

If I arm a track in PT and record with nothing plugged in i get the following.

Min gain - peak = -84.6
Max gain - peak = -51.4
 
Is this with the gain turned all the way down? What sample rate and resolution did you use? Could you perhaps attach a sound sample?
 
Steenamaroo,

I would appreciate that, especially if you could record it at 16-bit 44.1 kHz. I have discovered that the noise floor is highest on 16-bit recordings like the ones I posted above, which may perhaps explain why others using the same equipment are getting cleaner results.

I've been using Audacity in my recordings, but Audacity is apparently incapable of setting the sample rate and bit depth on the sound card on command. I've changed the sample rate and bit depth manually on Windows 7's Control Panel in order to force Audacity to record at 24-bit 48 kHz, the result of which can be heard in the sample below. The output is now much cleaner, but I'd still like to know whether the results I'm getting on 16-bit recordings are normal for the FireStudio.
 

Attachments

  • Presonus Noise (48 kHz 24 bits).mp3
    1.1 MB · Views: 6
Yeah, I'd be the same; I'd want to know.

My setup is pissin' about now *Throws things out of window* but i'll give it a blast in the morning for you.
 
Did you try sending the mp3 file of your test to Presonus support and get their insight on it? Sometimes they can provide tips and techniques on how to further lower the noise floor. Probably something isn't right in your signal chain and its important to be investigated. Or probably the Presonus audio interface has some issues that they need to know.
 
Last edited:
Steenamaroo said:


First have is minimum gain, second half is maximum gain.
Nothing is plugged in and I'm recording at 16bit / 44.1k
Click to expand...
Thanks. The difference is quite significant between our two recordings. I think I'll contact the retailer for a replacement.

Thank you all who took the time to reply. Your help is much appreciated.
 
Emerson Maningo said:
Did you try sending the mp3 file of your test to Presonus support and get their insight on it? Sometimes they can provide tips and techniques on how to further lower the noise floor. Probably something isn't right in your signal chain and its important to be investigated. Or probably the Presonus audio interface has some issues that they need to know.
Click to expand...
I haven't tried contacting PreSonus support, but at this point I think I'd rather have the unit replaced than go through the back and forth of tech support.
 
I've noticed something new: Recoding via the bundled Studio One application instead of Audacity produces recordings with much less noise, but I do have to push the gain on the Mic much higher to get a loud enough signal. I suspect the difference may be due to differences between the FireStudio's WDM and ASIO drivers. Programs like Audacity and the Sound Recorder app built into Windows 7 use WDM and produce loud and noisy recordings, while programs such as Studio One and Sonar X1 use ASIO and produce recordings that are much lower in volume and have very little noise.

Perhaps there's nothing wrong with my FireStudio after all? Can anybody confirm this behavior is normal?
 
Sorry, I can't help any further. I use a apple OS I'm afraid.

I'd recommend doing a recording using ASIO and comparing it to mine though.
 
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