My Latest Build, A Classic But Not A Marshall!

Discussion in 'Building the Classics' started by neikeel, Nov 18, 2018.

  1. neikeel

    neikeel Well-Known Member

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    Having built a clone of an Orange ORST (based on a rare amp that came into my possession for restoration):
    <iframe width="745" height="419" src="" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

    It sounds amazing as above and intrigued by the amps that Peter Green used during the early Fleetwood Mac years I decided to build one of these:
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    http://www.chambonino.com/work/matamp/mat2.html (more pics here),
    I acquired a couple of RS transformers and as Pleximaster seems to have cornered the market in JTM45s needing transformers I built this:
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    As you will see not an exact copy, I made it as a transition model never made between the one in the original pics and the ORST, so fuses on the back and loop on the front. I put replica on the top of the front panel and called it a 2020 (that's when I thought I was going to get chance to finish it!). I want to run KT88s in it but it appears EL34s were stock, but we shall see.
    Oh and this is next project, a handwired replica of Andy Powell's OR100:
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    Last edited: Nov 19, 2018
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  2. Timbo

    Timbo Member

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    Awesome stuff, I have never ventured into Orange Amps.
    Me like it!!!
    Schematic?
     
  3. neikeel

    neikeel Well-Known Member

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    upload_2018-11-19_8-27-57.png
    This is nearly correct.
    The 32uF can in preamp is actually a dual 16. One element is filtering v1 and the other the pi. Mains and screens are both 32uF.
    I would have liked to have used solid core wire for this one to get the wires to lie straighter on those long runs but the stuff I can source is either too far or too skinny.
     
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  4. Timbo

    Timbo Member

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    Awesome, Thanks muchly.
     
  5. jensvonbustenskjol

    jensvonbustenskjol Active Member

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    That's neat! Great build :)
     
  6. johan.b

    johan.b Well-Known Member

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    Up until sometime -73 the cathodyne p.i. On Orange/Matamp's was biased differently compared to -74 onwards.. in my opinion, the earlier version sounds much better( decoupled from previous stage and with a grid-to-cathode resistor)... I'm sure you already knew. Just mention it " just in case"..
    Cool project
    J
    https://drtube.com/schematics/orange/grmk2or2.gif
     
    Last edited: Nov 19, 2018
  7. neikeel

    neikeel Well-Known Member

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    As you will see this is the earliest Matamp I could find, the PI is the same as the ORST from 69 and the OR100 from 70. I have drawn up a schem for the ORST and a kind gentleman (thanks Stu) supplied me with an OR100 schem that has some subtle differences from Andy's (pre amp couplers, Drive switch and 'bright' cap and NFB resistor). The earliest ones don't have that resistor, I don't have any post 74 Oranges and all the schems I have are pre-74 but I will ave a look!

    This is an the ORST schem:
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    this is the OR100:
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    None of these have the grid-cathode resistor!

    The amp you link to is a relatively uncommon (Pix only variant) which has the pcb mounted preamp tubes and the mid lift inductor. I have one of those with me at the moment and had another last year. This one is quite bright and shrill (vs my 73 OR120) and vs the one I had last year which was a very nice amp, so I think there is variability even in the Orange years (as you know there was huge variation in the OR100 and GRO years).
     
    Last edited: Nov 19, 2018
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