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Markacoustic AH250 input impedance question

Discussion in 'Amps, Mics & Pickups [DB]' started by Seba, Jan 13, 2012.


  1. Seba

    Seba

    Oct 4, 2010
    Antwerp, Belgium
    Hi Guys,

    So I finally got myself the Markacoustic AC121 combo, which sounds absolutely amazing! It has the AH250 head, I'm a big fan. I do have a question about the input impedance of the two channels. Channel 1 is 500 Kohm (unbalanced jack, meant for pick up), channel 2 is 1 Mohm (unbalanced jack and balanced XLR, meant for microphone). I'm using a fishmann full circle pu on my upright.

    I tried both channels with the eq and filters flat and I find that channel 2 (1 Mohm) has a much more open and bright sound, more natural. I'm definitely using that one as my main channel. Problem is that doesn't have a mid control (which might come in handy in loud situations) and that I won't be able to combine the pick up with a microphone as I'm allready using the microphone-channel. Too bad because this was one of the main reasons that I bought this combo.

    Question: why does the channel with the higher impedance sound lighter and more natural (the volume is significantly lower, though) and is there a way to change the impedancy of the first channel to 1 Mohm?

    Thank you!

    Seba
     
  2. GrowlerBox

    GrowlerBox

    Feb 10, 2010
    Nude Zealand
    I responded to this question on the BG side.
     
  3. Seba

    Seba

    Oct 4, 2010
    Antwerp, Belgium
    Thanks!
     
  4. According to Markbass customer service, both channels have 500Kohm impedance. Strange for an "acoustic" combo, but I think that the input impedance is only one element of the whole design of an amp and Markbass is the proof that 500Kohm input works excelent with modern piezos like Realist or Full Circle.
    I wonder myself why the two channels of the Markacoustic amp sound so different from each other and the answer is probably they are voiced differently. I also prefer channel two.
    In my opinion, when blending mic with pickup into this combo, you need the mic to dominate, otherwise it gets killed by the pickup. In this case it's fine to use channel 1 for pickup as it should be used only very soft anyway.
     
  5. Seba

    Seba

    Oct 4, 2010
    Antwerp, Belgium
    Thanks for you reply! What do you mean when you say that the inputs are voiced differently?
     
  6. That basicaly means they sound different. Because they apparently have the same impedance input, the only reason why they should sound so different from each other is they are voiced differently by purpose.
    As the channel one sounds darker compare to channel two, maybe it's more suitable for bright sounding pickups, like Underwood or BP-100. Who knows, this is just my way how to explain the different sound of each input.
    By the way, I'm using the AC-101 combo and I start to like it. Very open, mellow and deep sound. I like to put it on a stool or high bar chair.
    It sounds great on larger stages where there is enough space around. In very small clubs, especially at those medieval cellars, where clubs in Europe sometimes happen to be, I prefer my GK 150MB combo for it's tight low end.
     

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