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Preamp noise
Old 30th March 2003
  #1
Schnert
Guest
Preamp noise

At home I have an Avalon AD2022 and a Focusrite Platinum thingy. The thing is, the Avalon gives me more noise than the Focusrite..... The Focusrite "beats" the Avalon in the hiss department, but there seems to be a 50Hz problem with the Avalon. If someone would have a listen to this little snippet of amplified noise from the Avalon, and tell me if this is a pure "50Hz problem":

Avalon

I've tried every single wall wart in the building, earthed or not, balanced or unbalanced outs, and the noise is the same everywhere. Why would the Avalon give me this and not the Focusrite? And how would I best get rid of it?
Old 30th March 2003
  #2
Lives for gear
 
bjornson's Avatar
 
🎧 15 years
My guess you've got a serious ac issue. Do you have anything with an electric motor on the same AC leg? Have someone take a look at your power with an Oscope, or better yet get a little furman balanced power supply/ups.
Old 31st March 2003
  #3
Schnert
Guest
I brought the Avalon to the studio, hooked it up, and the same noise/hum happened there. Heard nothing of it from any other preamp. I think I may have been too quick in my conclusions though, since I checked this with no mikes attached. When hooking up a mike, the hum seems to disappear, but of course, it may also have been somewhat masked by the noise from the mic itself. Any reason for hum to be present because no mike (nor cable)is connected? Any idea why this would only happen to the Avalon (the hum also disappeared when I lowered the impedance on the input)?

Just curious me
Old 1st April 2003
  #4
Moderator
 
Tim Farrant's Avatar
 
🎧 15 years
Generally speaking, a mic preamp needs to have a low impedance source (microphone) connected before it will operate to it's best noise performance. It depends on the design but this is a general rule of thumb. Without the source impedance, the input is "floating in the wind" and is prone to pickup of external feilds such as 50Hz hum. Also, the hiss level will be higher. I bet if you connected a 150 ohm resistor to the input on both the Focusrite and the Avalon, the Avalon will be quieter.

If it sounds OK with a mic, then it's fine.

Cheers
Tim

Buzz Audio
Old 1st April 2003
  #5
Lives for gear
 
Mike O's Avatar
 
🎧 15 years
Can't really offer any help with your issue other than to say my 2022 is one of the quitest pres I have. Mic attached or not. About as noiseless as it gets...

I am sure that helped your frustration level!
Old 1st April 2003
  #6
Schnert
Guest
Damn Mike, Tim gave me some comfort and then you come along and open the wound again

We have 220v~50Hz here, so I don't know if that would make it more susceptible to pick up noise with nothing attached. Seems fine with mics attached though, although I would feel slightly better if I was 100% sure that the Avalon is as it should be
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