chanel strip with buzzing noise

Discussion in 'Mixing & Song Critique' started by PhantomBox, Nov 27, 2009.

  1. PhantomBox

    PhantomBox Active Member

    Apr 22, 2006
    Caracas - Venezuela
    A while ago I custom built some 2 channel modules from an Amek Angela console (2 channel-strips into one metal enclosure with its own independent psu. As these channel-strips have no ballanced output I made one for each module by using a NE5534 opamp). Even in my workshop witch has a lousy AC power condition they all sounded great and even more so in the customers professional recording studio. Now the customer moved into another location and suddenly those modules are making a strange noise that sounds more or less like a buzzing that increases the farther the faders are turned down and vice versa. I tried switching the NE5534 to a TL072 opamp (different schematic, same output) but the noise remains.

    I'm starting to think that it might be a condition given by the AC power conditions at the customers new location, since my workshop is located in the basement of my home and doesn't induce any noise, while the customers new location is in a mixed commercial - residential area and maybe some neighbors with 2.4gHz cordless phones or cellphones (or microwaves, or TV sets, or whatever comes to mind) could be the cause for this?
    Does anyone know how you could shield these modules against any kind of possible interference? Or do you think this "buzz" might have a completely different origin?

    Any help is welcome.
  2. Link555

    Link555 Well-Known Member

    Mar 31, 2007
    North Vancouver
    So when you lower the gain the noise increases?

    How did you ground the strips?

    I would also suspect the AC mains as being the orgin of the noise source.

    Oh and as for output balanced line drivers there are many. Like the SSM 2142, or the THAT1646.

    While a NE5534 will work just fine if you layout and resistor matching was closely controlled, these "all in one chips" are simple and take care of that for you.
  3. RemyRAD

    RemyRAD Member

    Sep 26, 2005
    Somewhere he has plugged in a computer switching power supply with a ground pin. So now you have a ground loop and noise on the ground bus. Cheat the power supply grounding. Also look for any light dimmers on the same circuit. 5534's are bipolar input while the ILO71 is a superhigh impedance JFET inputs. If you run these as balanced differential inputs to simulate a balanced input transformer, then you're dealing with a balanced circuit. If you are using these as output devices you have to run a pair to create an active balanced differential output. But the ground loop problem can still wreak havoc. Even in a balanced circuit, noise on the ground bus can still modulate your audio. So it might be clean & quiet but your audio will still be far from perfect.

    5534's can also drive 600 ohm inputs up to + 18 DBm, such as blackface 1176/LA 3's, etc.. The TL 0 72 can't drive such a load. They just don't have the output current drive. They really aren't good output devices but nice clean input devices.

    Two of my favorite chips. Can't eat just one
    Mx. Remy Ann David
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