Re: Firebox -- hum, squealing, hiss


"Jack" <mistercuddles@xxxxxxxxxxx> wrote in message
news:1140393710.213968.175380@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hey everybody. I am investing tons of time and money on a studio
setup. I am not a pro-audio guy -- I'm just an artist who wants a to
get his ideas down. I was hoping that you incredibly smart pro-audio
guys could help me diagnose a major problem I have with the Presonus
Firebox:

When recording using a Shure SM58 and other dynamics, I get a high
pitched squeal on channel 1 and 2 (8kHz-16khZ) and a loud hum
(1kHz-2kHz) on channel two only. A sample of what I'm talking about
can be found at www.jacksbrain.net/noise.mp3 . The presonus website,
along with all the reviews I have read, says that the Firebox is
"ultra-low noise" and "pro-quality". Why can't mine be like that?
Here is my setup:

1: Shure SM58 on channel 1. Gain is at 3:00
Samson S1 on channel 2. Gain is at 3:00
2: Firebox powered by external AC source
3: 6-pin to 4 pin firewire cable into an all-in-one USB/Firewire port
that came with my laptop
4: Compaq presario 1.86 GHz, 1Gb Ram, Cubase.

Other stuff: When I put my laptop in standby mode, so that the blue
sync light turns red, the squealing and humming goes away.
Unfortunately, I can't record like that. Also, the hum is only around
when a mic (any mic, on or off) is plugged into Channel2, although
lifting the ground on this mic does nothing. Also

Here are my suspicions:
AC power is dirty?
All-in-one firewire port is incompatible?
Microphones don't provide enough signal to overcome SNR?

PLEASE help me out. I have spent lots of money on this setup and I
have nothing to show for it. Presonus tech support has been telling me
that "We are familiar with the sounds you are describing," but "theres
not much we can do" and "thats just the way it is." If anyone can
offer some better advice than this, I'd be very grateful. Please post
and email your replies. I may not check this group frequently.
Thanks!!!


I'd guess power supply problems. I went through something like this with my
Dell laptop. It was an MAudio Transit, not a Firebox, but the symptoms were
similar. I plugged a ground adaptor onto the laptop's power cord (which
interrupts the power cord's ground) and the problem disappeared. So I went
out and bought one of these:

http://www.ebtechaudio.com/new.html

Yeah, I know; it's expensive (street price around $65). But using the
ground adaptor is just asking for trouble, and possibly electrocution. It
is, however, a way to test and see if you're having the same issue I was. I
never had the problem on a regular PC; just the laptop. I suspect it has
something to do with the way the laptop power supplies handle their
grounding.

Cheers,
Walt


.