Apogee duet - hiss/white noise normal after a certain level of gain? at DVinfo.net

Josh Bass · June 25th, 2011, 03:31 AM

Don't know if anyone has one of these, but I have an Apogee Duet audio interface I use with my Imac to record music and voices.

Noticed some hiss/white noise today when trying to record.

Googled and found some folks have had issues. . .could be the box, could be the breakout cable.

I start to SEE the noise on Logic's (what I normally record into) meters (hard to tell exactly how loud it is. . .Logic meters don't go below -60, and its "two bars" tall) when the duets inputs are at 50. . .and I can hear it with my monitors at about 55.

Tried a few experiments like unplugging everything from the inputs, turning on phantom power, turning inputs up. Noise is still there. Phantom off? Noise still there. Unplugged all power cords going into same strip as Imac, literally leaving nothing but the mac (apogee is powered by virtue of being hooked up via firewire, doesn't have power cable), still there.

Wondering if this this is supposed to be totally noise free (or in the audible range) even when inputs are cranked? Or am I expecting too much.

Input levels range from 10 to 75, and I usually have to be in the mid 50's to early 70's to get good recording levels, depending on what I'm recording.

Already sent it in once before, not too long ago, but I believe it was my fault for unplugging and replugging in mics with phantom power switched on (a no no).

Definitely hiss/white noise, not room noise, as, to reiterate, I can hear it with nothing plugged in to the inputs, same quality of noise as when I have a mic hooked up and recording.

Steve House · June 25th, 2011, 05:35 AM

Unterminated inputs present higher noise levels than you would encounter in normal use. You would get a truer impression of the actual circuit noise if you short the each input's signal hot and cold together (XLR pins 2 and 3) with a 100k or so resistor.

Josh Bass · June 25th, 2011, 06:32 AM

Is that something someone with little to no understanding of electrical matters could safely do on his own?

Did a whole bunch of tests just now.

There was an electrical component to the noise (a bzzzzzzzzzzzzzzzzt kinda thing). Believe that had to do with my fw400 port. Switched the firewire out of the duet to go into my lacie that's plugged into my fw800 port, that component of the noise is gone, though the white noise persists (maybe a little better).

Also tried setting both inputs 1 and 2 to 0. That kills the noise. Although the noise only becomes noticeable/visible on a dbfs meter when the inputs are past 50 anyway.

June 25th, 2011, 03:31 AM	#1
Josh Bass Slash Rules! Join Date: Apr 2002 Location: Houston, Texas Posts: 5,472	Apogee duet - hiss/white noise normal after a certain level of gain? Don't know if anyone has one of these, but I have an Apogee Duet audio interface I use with my Imac to record music and voices. Noticed some hiss/white noise today when trying to record. Googled and found some folks have had issues. . .could be the box, could be the breakout cable. I start to SEE the noise on Logic's (what I normally record into) meters (hard to tell exactly how loud it is. . .Logic meters don't go below -60, and its "two bars" tall) when the duets inputs are at 50. . .and I can hear it with my monitors at about 55. Tried a few experiments like unplugging everything from the inputs, turning on phantom power, turning inputs up. Noise is still there. Phantom off? Noise still there. Unplugged all power cords going into same strip as Imac, literally leaving nothing but the mac (apogee is powered by virtue of being hooked up via firewire, doesn't have power cable), still there. Wondering if this this is supposed to be totally noise free (or in the audible range) even when inputs are cranked? Or am I expecting too much. Input levels range from 10 to 75, and I usually have to be in the mid 50's to early 70's to get good recording levels, depending on what I'm recording. Already sent it in once before, not too long ago, but I believe it was my fault for unplugging and replugging in mics with phantom power switched on (a no no). Definitely hiss/white noise, not room noise, as, to reiterate, I can hear it with nothing plugged in to the inputs, same quality of noise as when I have a mic hooked up and recording. __________________ The Bass' camerawork The Bass on IMDB

June 25th, 2011, 05:35 AM	#2
Steve House Inner Circle Join Date: Mar 2005 Location: Hamilton, Ontario, Canada Posts: 5,742	Re: Apogee duet - hiss/white noise normal after a certain level of gain? Unterminated inputs present higher noise levels than you would encounter in normal use. You would get a truer impression of the actual circuit noise if you short the each input's signal hot and cold together (XLR pins 2 and 3) with a 100k or so resistor. __________________ Good news, Cousins! This week's chocolate ration is 15 grams!

June 25th, 2011, 06:32 AM	#3
Josh Bass Slash Rules! Join Date: Apr 2002 Location: Houston, Texas Posts: 5,472	Re: Apogee duet - hiss/white noise normal after a certain level of gain? Is that something someone with little to no understanding of electrical matters could safely do on his own? Did a whole bunch of tests just now. There was an electrical component to the noise (a bzzzzzzzzzzzzzzzzt kinda thing). Believe that had to do with my fw400 port. Switched the firewire out of the duet to go into my lacie that's plugged into my fw800 port, that component of the noise is gone, though the white noise persists (maybe a little better). Also tried setting both inputs 1 and 2 to 0. That kills the noise. Although the noise only becomes noticeable/visible on a dbfs meter when the inputs are past 50 anyway. __________________ The Bass' camerawork The Bass on IMDB