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G-K MB150E owners - help dialing this puppy in, please...

Discussion in 'Amps and Cabs [BG]' started by HeavyDuty, Aug 20, 2005.

  1. HeavyDuty

    HeavyDuty Supporting Curmudgeon Staff Member Gold Supporting Member

    Jun 26, 2000
    Suburban Chicago, IL
    I'm easily distracted by shiny objects and too many knobs, so...

    Can anyone give me a hand with getting my new MB150E/112 dialed in? I figured out the pre and post gains and EQ and am getting decent, usable tone, but am unsure about use of the limiter and boost.

    From the manual, the limiter allows you to control the output wattage. Does that mean that when the limiter is out, the amp develops full power? Can anyone give me an example of when you'd use the limiter?

    Boost - is it simply a tone control, or is it affecting output power? (The schematic implies tone only.) If I use the footswitch, does boost toggle between off (full CCW) or full on (full CW) and whatever is dialed in?

    Finally, how do you normally dial in when you're looking for maximum usable volume? I assume it's whatever I've dialed in before but with the post ("Output Level") dimed. I'm not expecting it to run with my WT-550, but am curious in case I go visiting with the little critter.

  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I have had a MB150 for many years.

    Boost basically gives you gain through a stage that also has some mild distortion. For typical electric basses, start with the knob all the way down.

    The limiter is crappy. Sorry to put it so bluntly. First of all, it makes a lot of hiss. Second, it is a soft knee compressor whose purpose I cannot fathom. I have even tried to figure it out with signal generator and oscilloscope. The limiter will not prevent you from driving the power amp to clipping.
    I have the schematic too. There is a Class-A JFET gain stage in the boost circuit, which implies some controlled nonlinearity.

    Start with the master volume as high as you can tolerate. Boost at minimum. Adjust the input gain until you have the desired volume. If you have really weak pickups (my homemade upright bass magnetic pickup is an example), you may need some help from the boost knob.

    Not to give you buyers remorse or anything, but I must say that if I was going to buy another one of these, I would get the much simpler MB150S. But when I bought the MB150E, the salesman lied to me and said the MB150S was discontinued.

    As I mention to all MB150E owners, the best thing to do is throw it out a window, where it will land in a UPS truck heading for my house. For all of my complaints, I stick with this amp because it really sounds good and is unbeatable in terms of ruggedness and portability.

    I should mention that I have an older MB150E. If the newer series is different, then I might be wrong about its circuit design.
  3. HeavyDuty

    HeavyDuty Supporting Curmudgeon Staff Member Gold Supporting Member

    Jun 26, 2000
    Suburban Chicago, IL
    Thanks! Trust me, for $200 there's no buyer's remorse here...

    OK, so there *is* gain in the boost stage - my ears weren't lying. I don't have a full blown schematic, just the block diagram that's in the manual. So full CCW removes it from the circuit, or is it a cut?
  4. I have an GK-150 MBE - the "boost" control is in the "foot-switch" section along with the "chorus" control. You can use a foot-switch (or two) to bring either/both of those effects into play when soloing. From what I remember, if the footswitch isn't plugged in, the "boost" control is in the circuit, so that you don't need a foot-switch in order to use the effect, so I've always kept the boost set to minimum (I have a dual foot-switch but never had need of either "boost" or "chorus"). I always have the "limiter" switched "in" and set fully clockwise.

    Hope this helps -

    - Wil
  5. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The boost circuit is never bypassed. But like most circuits that introduce mild distortion, the amount of distortion is minimal if you feed a low level signal through it. My advice, crank it down and don't worry about it.

    Now I have to confess that I use the MB150E by itself for electric bass, but when playing upright, I use an outboard preamp going into the aux input, which bypasses the internal preamp.
  6. Bass-only

    Bass-only Supporting Member

    Oct 9, 2001
    On my MB150E, I follow what the 1001RBII manual said to do with the BOOST, which was to put it a 12:00. I even called G-K and they recommended leaving it at noon (and adjusting from there, as desired).

    It always bugged me that in the "setting up your sound" section of the (MB150) manual, it never mentions what to do with the BOOST control.

    I leave mine at 12:00 and (sometimes) use the MB extension cab also. The extension cab really opens up the bottom end!

    If you use this amp within reasonable applications, it's one of the best small combos around.

    Now - with that said (and nothing to take from the MB series) but it you want a relatively small combo with a HUGE sound, check out the Mesa Walkabout Scout! Note - it's still - it's 20 pounds heavier that the MB150E AND MB ext. cab combined!

    Back to the subject at hand - the MB150E has served me well for many years. When I use it without the ext. cab, I mount it on a mic stand and put it about 4' in the air, angled slightly up, and have it about a foot away from my back. Since we run everything through the mains, it serves it's purpose fine.
  7. HeavyDuty

    HeavyDuty Supporting Curmudgeon Staff Member Gold Supporting Member

    Jun 26, 2000
    Suburban Chicago, IL
    Cool - thanks for all the help! I'll keep on playing around and see if I can break it.