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Help with Wharfdale EVP X15

Discussion in 'Monitoring / Headphones' started by Keary, Jul 18, 2012.

  1. Keary

    Keary Active Member

    guys, we were at practice tonight and the mic was plugged into the EVP and began to feedback. It wasn't a heavy feed, though it is never good but we got really concerned when a light began to shine inside the wharfdale amp. No explosions or smoke (thankfully) and the amp still works. It even stumped our local electrician who recently got the power back working.

    The front of the amp has 2 speaker cones. To the left and right are holes where the light shone through. It was a serious light too, like a household bulb!!

    Been looking on the website for answers but to no avail, so thought i would try the next best place.

    Anyone have any idea what is going on?
  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    It IS a light bulb!
    This is designed so that excessive power going to the cabinet will be "absorbed" by the bulb instead of burning up a speaker component. Kind of archaic, but it works and many of the cheaper cabs on the market have this to protect the drivers from being smoked. It is not fool-proof so you still need to turn down the volume!
  3. Keary

    Keary Active Member

    Thanks very much for your time moonbaby. This was my first thought on the matter, but wanted to seek out advice just to be sure. We never take the volume above 30% while using it, but the feedback will not conform to volume levels set, right?

    You have made our week!! The amp crashed last week due to excessive vibrations, so the local electrician told us, but he never mentioned light bulbs inside.

    Thanks again moonbaby, you are a star thumb!!
  4. RemyRAD

    RemyRAD Well-Known Member

    There is a detrimental effect from utilizing a lightbulb to limit the current to the speaker. It's a very fine filament which actually make the sound, sound a little more squeezed and less open. But those speakers were not designed to be PA speakers. They are hi-fi speakers. They're not designed for PA style abuse and they won't last long that way. Even with a lightbulb.

    It's pretty funny I had a console 20 years ago made by Sphere of Chatsworth California. All of the operational amplifiers for the output had lightbulbs on the output driver cards. One for each output transistor in the push pull circuit. These were not designed as current limiting lightbulbs. Instead, it output transistor blew and shorted out, it wouldn't take down the entire power supply feed to the others. The lightbulb would light indicating which output transistor was blown. It was certainly easy to tell. And there were folks that said they actually thought those output amplifier sounded better with the lightbulbs than without the lightbulbs. I never bothered to find out about the difference. Same output circuitry in their equalizers with no lightbulbs. And those sounded super sweet. I miss those. The Neve's are great but those Sphere's were killer sounding. Quasi-Parametric's & 9 band graphics. Brother do I miss those. I love my Neve but I'm almost sorry I sold that Sphere.

    Walk into the light!
    Mx. Remy Ann David

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