Noise floor of usb interface itself

R

roelsl

New member
Hi to you all,

I am starting as a voice over and have a question about noise floor. My setup:

Neumann TLM 102 > ART USB Dual Pre Interface > WIndows Laptop > Adobe Audition 3

When I unplug the mic and just connect the usb interface alone (without any signal coming in to it) I have a noise floor of about -55 db. I guess this is the internal noise of the usb interface, right? When I connect the mic and set the gain to my usual recording level, my noise floor is about -50 db. I wonder if that -55 db floor with the interface connected and just running idle, is normal? How can I reduce that floor? My studio booth is prettu air and sound tioght, it's the usb interface I am worried about, I guess?

Thanks guys!
 
I don't know the ART interface you're using but that noise figure sounds WAY too high to me even with the gain cranked up.

The ART manual agrees with me:

Signal to Noise Ratio: >90 dB (Ref 0 dBu)
Equivalent Input Noise: -120 dBu typical (XLR balanced, gain @ maximum)
Click to expand...

If the unit is new it might be time to return it under warranty.
 
How are you measuring the noise floor?

Is that -55dBFS a peak number from when you turn the unit on or is that the RMS level of the noise

So to pose the question another way, does the noise pop up to -55dB dBFS on your DAW meters when you first turn it on and then drop down to -90dBFS (although the DAW meters keep that -55dBFS recorded as the maximum peak) or is it sitting constantly at -55dBFS
 
Does the noise floor reduce if you run the lap top on battery with the mains lead disconnected?

Alan.
 
Hi Bristol Posse,

That -55 dBFS is an average of several minutes, always there. I plug in my usb interface and get a short peak and then I get a constant incoming signal around -55 dbfs. When I record my voice, it peaks at around - 6 dbfs. I come out of the studio, unplug my mic, watch the meters and see that -55 dbfs sitting their constantly, with just my interface connected and no incoming source.

In the Windows Sound and Audio setup, I have set the RECORDING INPUT level of that usb interface (called AUDIO CODEC) in the devices overviews at only 25%. The more I open the input recording volume there in WIndows , the higher the noise floor is getting , even and still with nothing at all connected to that ART device.

DOes this make sens to you guys?

Thanks!
 
You have a -55 db noise floor at 32 but float? You may have a grounding issue in the house wiring. Try it on another circuit or even in another building before you return it.
 
It's probably because you are using that cheap little converter - a $49 preamp D/A converter which is known for being noisy - I have an ART TPS and it works great, but I haven't heard anything good about those little Duel Pre's

but it could totally be a grounding issue - you have any light dimmers or fans in your studio?

PS - I could be looking at the wrong model Duel Pre - like I said I have never used one and it might be just fine :o
 
arcadeko said:
It's probably because you are using that cheap little converter - a $49 preamp D/A converter which is known for being noisy - I have an ART TPS and it works great, but I haven't heard anything good about those little Duel Pre's

but it could totally be a grounding issue - you have any light dimmers or fans in your studio?

PS - I could be looking at the wrong model Duel Pre - like I said I have never used one and it might be just fine :o
Click to expand...

Ok ... so any idea of a digital interface with a really low noise floor and in the $150 to $200 range?

Thanks
 
Hi all,
I checked 3 A/D USB Interfaces today, all without a mic connected, so just the interface alone. My ATR I mentioned earlier gives me around -55 db noise floor. A Numark interface gave -51 db and the T.Bone (cigar style device) gave me -55 db. Way too much noise coming in as far as I'm concerned but does not much change with other types. So I am more and more convinced that my laptop is the problem. I m using a modern Toshiba Satellite laptop. What am I doing wrong? How can I lower that noise floor?
And please keep in mind that my studio/vocal booth is very quit and does not count now because I am measuring noise floor without anything conncted.
Thanks!
 
2 Weeks ago I asked this "Does the noise floor reduce if you run the lap top on battery with the mains lead disconnected?"

Instead everyone tells you this interface is no good tray this one don't use a cheap one etc. Today even cheap interfaces (not the original in built ones but external USB or firewire) have a signal to noise that is well within spec for good recordings, I have recorded a lecture using a cheap Behringer 16 bit USB card and the signal to noise was so good you could hear the audience breathing hen nothing was being said.

So what was the answer? This will help me track down the problem which I would think will be a digital earth loop between the mains and the USB cable caused by an earthed laptop power supply.

Alan
 
battery or not, no difference

Ok, as you said, I recorded two session, one with my laptop in the power plug and another just running on batteries. No difference at all ...

I do everything right, I suppose?
Just connect the interface with USB cable. make sure it is my input source for recording:
CONTROL PANEL > SOUND > RECORDING Tab
There I enable 'USB Codec' and set the input level to 20 (out of 100). The louders I put this level, the more the noise I hear.

regards,

roelsl
 
As I understand it, you can't assess the noise floor with the input floating or un-terminated.

If the input is balanced, you could connect a 150ohm resistor between pins 2 and 3 of an XLR, or tip and ring of a phono plug. That kind of emulates the impedance of typical microphones. Or you could just use wire between pin 2 and 3 (or T and R) to see if the device is just inherently noisy.

Paul
 
@Roelsl,

Looks like you fixed your problem, and your last note was moving in a similar direction to a lot of other advice I've seen from people working with the Alesis MultiMix 4 USB. They've recommended setting the input level on the PC right down to 3 - 5 out of 100 to get the best Signal to Noise out of their mixer.

What happens if you decrease the USB Code recording "Level" in CONTROL PANEL > SOUND > RECORDING Tab even more than you already did, with corresponding increase in the output on the mixer?
 
One other thing to think about here:

You're putting a $700 microphone through a $60 interface and wondering where the noise is coming from???

Step back and think about that for a minute....
 
ALL props to Tim O but the problem is Windows 7.

You have set the volume level to 20 ref 100? Got to go lower, 3 or 4!

I just plugged my A&H ZED 10 into a P4 XP machine and Samplitude 8se reports a baseline noise of -91dBFS.
Did the same with a Toshy i3 W7/64 laptop, -81dBFS . Got into volume levels and cranked it down from 10 to 3 and got -90.8dBFS!

Trouble is W7 "sees" all generic driver usb audio devices as microphones! Things usb with proper drivers, my Fast track pro and KA6, not a problem.

But Tim is right, you could really do with a better interface. My NI KA6 has noise floor of -101dBFS. You will spend a LOT more than 200quids to better that and then not by much!

Dave.
 
Did you guys notice this thread was a year old? It seems to be a common issue with most budget mixers that have USB output - setting the USB output level too high gives some kind of noise. My Mackie ProFX12 does the same thing. Not unexpected - it's a mixer with an inexpensive A-to-D converter thrown into it.
 
mjbphotos said:
Did you guys notice this thread was a year old? It seems to be a common issue with most budget mixers that have USB output - setting the USB output level too high gives some kind of noise. My Mackie ProFX12 does the same thing. Not unexpected - it's a mixer with an inexpensive A-to-D converter thrown into it.
Click to expand...

Sorry but no. I had this issue with my A&H mixer when I fed it into my W7/64 desktop. If you use XP (I have 3 XP machines) the mixer's converter level is automatically set right. As I said, for reasons only known to Msoft, W7 sees simple usb AIs all as microphones and gives them max gain by default.

This information came directly fro A&H who not only make excellent mixers but are very helpful chaps to boot!

Dave.
 
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