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Resonance distortion?

Discussion in 'Amps and Cabs [BG]' started by ghindman, Feb 11, 2006.


  1. ghindman

    ghindman

    Feb 10, 2006
    Hello,

    I have an older Avatar b210 Delta fed by an SWR 350x Pro, and either a Fender J, or a Stingray5. Since the b210 is an older model, and I wanted to be able to use the speakons on my SWR, I ordered a new input plate from Avatar.

    Since I've replaced the plate, I get an odd fuzzed distortion with certain notes. It's not strictly low notes, so it's not over excursion, and it's not constant -doesn't happen at low volumes. The distortion also has kind of an odd wave-like oscilllation characteristic to it, like a flanger, or a string played just slightly out of tune with another. I'm wondering if I'm getting some kind of weird resonance phase oscillation in the more complex crossover, or something similar. Anyone have any ideas how I'd go about troubleshooting this?

    thanks
     
  2. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Without hearing it it's hard to comment. However the new crossover did raise my eyebrows. It's a 2nd order filter, (meaning it's a 12dB per octave filter) and these are known to introduce some phase issues. However, it would manifest itself as certain notes being less audible. The sort of oscilation doesn't scream of phase issues to me.

    However, the other thing about the new crossover I found interesting was the use of the inductor with an magnetic iron core. They work well enough in Hi-Fi where wattages are relatively low (<100W), but they are known for introducing distortion into the signal at higher wattages. An inductor with an air core would have been better, but would have cost more, and with Avatar being foremost about price, the cheaper inductor got the nod. This could explain the distortion, but not the oscilation. That part has me stumped.
     
  3. ghindman

    ghindman

    Feb 10, 2006
    The oscillation is very subtle, just as the note is decaying. If I strike a string, the initial distortion is a fairly loud static/fuzz distortion which decays in volume with the plucked note, and I can hear the oscillation towards the end of the decay. Hrm, I may just slap the old input panel back in, and put the sucker up for sale.

    Thanks for the input.
     
  4. ghindman

    ghindman

    Feb 10, 2006
    Threw the old input plate in, distortion is gone. Very strange. I'm a little suspect of these new panels from Avatar. The first one I got was DOA - the circuit board for the crossovers sits right down on top of the speakon solder tabs and it was shorted. Second one had the same clearance issues, so I put a couple of nuts as spacers on the legs to give it some more room, but still had this distortion problem. 'spose it could be a coincidence, but doesn't feel like it.

    I must say, though, first and only problem I've ever had with Avatar, and when I called with the first dead board, they shipped a new one out free of charge.