Wharfedale 8.2 active monitors hiss when nothing playing?

Discussion in 'Monitoring' started by AngryMonkey, Dec 26, 2008.

  1. AngryMonkey

    AngryMonkey Guest

    Upon several recommendations from this and other forums I bought a pair of Wharfdale 8.2 Diamond pro active monitor speakers.

    Ive just plugged the power in, turned them on and without even plugging in a music cable yet I can hear a hiss (on 1/4 volume, which is quiet).

    This is extremly frustrating, does anyone have any ideas why this may be happening?

    If I turn the volume up to 1/2 on the back of the speakers the hiss is quite audible and there is also now a humm (sounds like a 50hz electric hum).

    Ive tried plugging the music cables in (both XLR and normal jack types) but no difference.

    Its been suggested I may not be grounded properly but im not sure how to test/solve that?

    Thanks in advance,
  2. RemyRAD

    RemyRAD Member

    Sep 26, 2005
    I really would rather not spank a monkey so, I'd be very cautious with the problems you are describing. Most amplifiers at idle produce a small amount of residual noise. But from what you are describing, this could be from some sort of RF interference? What you actually could be hearing is modulation noise from what could be ultrasonic frequencies that will burn your tweeters out that you can't hear. You'd not be the first person this has happened to. Not particularly from this manufacturer or model in particular but in other studio situations as well, this has happened. For example, the bias frequency of analog tape machines were generally between 80kHz to 235kHz. Most machines had "bias traps" to prevent these ultrasonic frequencies from making their way to your speakers. But plenty of tweeters have been blown out over the years because of that. You wouldn't necessarily know it was happening until you smelled it. Which of course, was too late. Nothing like the smell of fresh fried speakers in the morning!

    When you're dealing with these electronically balanced inputs they are not always going to respond like transformer balanced inputs. And in general, your grounding scheme may need to be reevaluated? Grounding in balanced inputs, with transformers, doesn't necessarily mean you have to connect the "shield" at both ends. With electronically balanced inputs, you generally need some kind of ground reference. And that's when the problems start a.k.a. ground loops. And these electronically balanced inputs when not connected properly can actually go into ultrasonic oscillation. This is just as bad as the bias problem as it essentially turns the chip into an ultrasonic oscillator.

    These are just my thoughts as to your problem. I'm not used to dealing with 220 volt 50 hertz electrical systems but that shouldn't make much difference? Still, without anything connected to the "Speaker" inputs at all, noise should still be minimal. Especially since most low impedance outputs present an input load of 25 to 150 ohms. So practically a short but not a short as that too can cause a chip to go into oscillation at ultrasonic frequencies. Maybe there's just not enough sand in your speakers?? I could send you a bucket? Let me know?

    Full of sand in my undies. Don't you hate that?
    Ms. Remy Ann David
  3. Boswell

    Boswell Moderator Distinguished Member

    Apr 19, 2006
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    Re: Wharfedale 8.2 active monitors hiss when nothing playing

    What was on the other end of the cables when you plugged them into the monitors? If nothing, then it's not surprising that you heard no difference.

    Make yourself a shorting XLR plug (male): solder a wire connecting pins 1, 2 and 3. Plug that into a speaker input and listen for any difference in the hiss or hum. If there is very little hiss/hum with the plug in, then all will be OK when you connect it up properly to the output of your powered-on interface or mixer or whatever it is you want to use the monitors with. If the hiss/hum is no different (or it's worse) with the shorting plug in place, you need to contact Wharfedale technical support.
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