Question about a slight noise from the receiver

Discussion in 'AV Receivers' started by Stan Rozenfeld, May 11, 2005.

  1. Stan Rozenfeld

    Stan Rozenfeld Stunt Coordinator

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    I've had my Marantz SR-18 receiver and my Atlantic Technology 370 5.1 Speaker System for about six years. I've discovered this "problem" recently strictly by accident, while diagnosing some other problem in the home theater system. Consequently, I am not even sure if it was always there, or if it's a recent phenomenon.

    When my receiver is on, but no music is playing, I hear a very slight noise (I would call it a hum, but it's so faint, I can't even call it that) when I put my ear right up against the speaker grill. I don't hear it at all from seating position or even when I stand right next to the speaker. Also, the "hum" is VERY slightly more noticeable when receiver is set to 6 channel input, then when it is set to digital input, but again only when I put my ear right up against the speaker grills and REALLY listen for it. This phenomenon holds even when I disconnect cable, dvd player and everything else from my system.

    I can't say that it really bothers me since it doesn't seem to affect performance, but I am just wondering if it's a normal phenomenon (this receiver was a flagship product in its day, after all), or whether I have a slight case of ground loop, some sort of interference, or something 'wrong' with my receiver?

    Anyone input will be appreciated.

    Thanks,
    Stan
     
  2. Leo Kerr

    Leo Kerr Screenwriter

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    This is called 'noise.'

    Apt, n'est pas?

    Basically, any analog circuit is subject to random, thermodynamic noise; can't be avoided. This is reflected in the specs for the amp: signal:noise ratio, among other things.

    The reason why the analog inputs are slightly noisier than the digital inputs are because not only are they analog through (rather than coming out of the D-A in 'silence') but the inputs can also act as antennae, collecting faint signals from flourescent lights, vacuum cleaners, and all sorts of other things.

    The only reason to worry about it is if the noise level changes suddenly and significantly.

    Actually, another possible source is if your amp has an internal noise-generator: it may be letting a little of that leak through, too, but still, it's background noise, and as long as you can't hear it except when you've got the speaker cone in your ear, don't panic.

    Actually, you should be careful about putting speaker-cones in your ears: the cone can act as a reflector and 'amplify' the noise from your body, similar to the 'ocean' in the sea-shell.

    Leo
     
  3. John S

    John S Producer

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    You know, we all like the banter about truth in amplifier section power ratings.


    We don't even want to get into how various manufactures in Mid-Fi Audio rate their S/N ratios!!!! [​IMG]
     
  4. Leo Kerr

    Leo Kerr Screenwriter

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    Actually, past experience with 'signal leak' was a factor in why I went with the then top-of-the-line Yamaha DSP-A1 - no internal tuner. You'd not believe the number of receivers that have FM signal bleed even when you've got any other input active..

    Leo
     
  5. Stan Rozenfeld

    Stan Rozenfeld Stunt Coordinator

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    Leo,

    Thanks so much for putting my mind at rest. I've been listening to sacds and cds for the first via anolog and have been rediscovering my music collection. It sounds great, and whatever the minimal noise, it certainly doesn't interfere with the performance.

    For the record, I too wish that there would be more receivers made without the radio tuners, i.e. integrated amplifiers, a feature that I never use.

    Thanks again,
    Stan
     

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