Orange Micro-terror... anyone know this amp?

Discussion in 'Amp Tech Center' started by jhundt, May 6, 2021.

  1. jhundt

    jhundt Doctor of Teleocity

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    My son (in Boise) has one of these and he enjoys it. Today he told me that he has a problem, and asked if I knew anything about it. Here's how he described the problem:

    "when i play my Orange Microterror for about 30+ min, it just loses all power, like the gain circuit is failing or something. So i can still play cleanly alright enough at that point, just the gain knob basically seems disabled... When it starts doing this, I can turn it off and on again and the gain works fine for a few minutes, then craps out again."

    I have done some searching, but I can't find a schematic. I know it's a single 12ax7 feeding a class-D power amp. I know nothing about how the 12ax7 is used. I kind of assume that the Gain knob is on one section, which feeds the second Volume section. But that is just a guess based on my old-school learning.

    Of course the obvious thing is to swap in a new tube. And I will tell him that. But I thought I would ask here first, and see if anybody knew anything or had any suggestions.
     
    crazydave911 likes this.
  2. LudwigvonBirk

    LudwigvonBirk Tele-Holic

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    My son has the same amp and had the same problem. I gave him a cheapo EH used 12ax7 tube, fixed it.

    As you may have noticed, young Micro Terror user dudes don’t need glassy-clean vintage glass, they need something that can handle heat and dimed settings.
     
  3. gusfinley

    gusfinley Tele-Afflicted

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    I've been trying to find a schematic for these since they came out - I may have found one I'll have to check. I would love to build one, though.

    By the way, the Power amp is not a Class D amp, its a 4-channel "Chip Amp" Like those found in Car audio equipment. It may be running in "Bridged mode" or only use one side.

    The 12AX7 runs off of around 15VDC, so it operates in "starved plate" mode. This adds a lot of distortion and a lot of compression.

    I have heard of some issues with the chip amp shutting down if run at certain impedances. I'll try to dig up some links. It looks like a minimum of 8 ohms is recommended.

    Here's some great info (including a schematic):

    https://www.freestompboxes.org/viewtopic.php?f=2&t=22030
     
  4. jhundt

    jhundt Doctor of Teleocity

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    thanks guys.
     
  5. tele-nova

    tele-nova Tele-Meister

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    Do you know the ohm rating for the cab he's using it with? If it is 4 ohms that could be the problem. I think it is 8 ohm minimum.

    The early versions of that amp said minimum of 4 ohms but users were complaining of the amp shutting down on them. Newer versions like mine are rated at the minimum 8.
     
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  6. printer2

    printer2 Poster Extraordinaire

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    Last edited: May 8, 2021
  7. ClashCityTele

    ClashCityTele Tele-Afflicted

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    +1 on this.

    Check out
    https://www.tdpri.com/threads/orange-micro-terror-issue.885493/
     
  8. jhundt

    jhundt Doctor of Teleocity

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    he says it is:
    "he speaker is an Orange PPC112, says it's 16 ohm and 60w"
     
  9. Mike_LA

    Mike_LA Tele-Afflicted

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    Micro Terror
    Tube preamp (Gain)
    Solid State Power amp (Volume)
    Loose gain ---> bad preamp

    Side by side with a tiny terror, pretty much the same everywhere except the low end. You need proper iron for that..
     
  10. radiocaster

    radiocaster Poster Extraordinaire

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    Mine says 4 ohms and I never ever had that problem, and I would usually run at at 4 ohms. Either there were two versions of the amp that said "4 ohms", or they were using it at a much higher volume than I was.

    Trying another tube is a no brainer.
     
  11. Asmith

    Asmith Friend of Leo's

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    With an SS output you would need to crank it to max out the power consumption
     
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