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Sunn Sonaro schematic (later version, not Sonic I-40)

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  • Sunn Sonaro schematic (later version, not Sonic I-40)

    Unless I am mistaken the Sunn Sonaro and the Sonic I-40 were the same circuit design, but there is also a later version of Sonaro that is different.

    The amp I have is from 1971. It varies from '67 version schematic. rather than 2xEL34s and a tube rectifier it has 2xKT88s/6550s and solid state rectifier. Also old version has 7199 phase inverter and later one had a 6AN8 I think. I actually forgot to look on this amp to see if it was 6AN8. It seems to be all original except maybe the orange drop on the ground switch? It has a 3 prong

    Click image for larger version

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    Anyone have schema I can reference against this one from '67?
    Click image for larger version

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  • #2
    You did say SS rectifier, but is this close?
    and a bit about rectifiers here:
    Last edited by g1; 08-25-2015, 06:29 PM.
    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey


    • #3
      In that era Sunn only had a few circuits, and they mixed and matched them to create different models. They did use EL34 and KT88, and the phase inverter tube changed depending on which output they selected. Here for example is a similar amp with the KT88s.

      WHat part of the schematic do you need? I mean, if the preamp is different, but you are working on the power amp, all you need is a good power amp schematic.
      Education is what you're left with after you have forgotten what you have learned.


      • #4
        Well, this amp works great but I will probably recap just to keep it reliable. It is a studio amp so it would be a bummer if it failed mid-session on someone.

        I'm going to make a version that has a Model T style output section and power supply with this front end. The studio loves this amp, and the engineers would like to use it live in their bands once in a while, but it's just not loud enough.

        See how I got the heaters layed out in the pic
        I am just looking for a true schematic for research.

        This is kind of an off the cuff experiment so if anyone has any build advice or sees reasons why this may not work well of course that's welcome too.


        • #5
          And those two schematics offered are helpful thanks. They seem closer to what I'm working with than my Sonic I-40 schematic.