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Marshall 2266 vintage modern Master volume for the high channel

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  • Marshall 2266 vintage modern Master volume for the high channel

    Hello. I have a 2266 which the customer has just purchased Used and really likes it., But he want s to be able to control the High channel ( controlled by the dynamic range button ) by putting a master volume on it
    I've had a test and there is a massive difference between the 2 channels with no way of controlling it.
    2266_C_2466_Pre-amp..pdf
    I believe i have found a suitable place to fit it at the junction of R15 between V2-V3. Going to fit a new mains switch with a neon and then remove the original neon so i have a space to mount the master volume

    any thoughts on this or better places to fit it
    many thanks Mr A

  • #2
    Is there a Master Volume between the tone stack and V4 ?

    R15 seems like a good place to insert a Master Vol, but it makes me wonder if low drive to V3 in the High Channel mode might make it sound restricted.

    Isn't what is really wanted is two Masters between the tone stack and V4 ? What circuitry is connect to CON9 ? Effects Loop ?
    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
    REMEMBER: Everybody knows that smokin' ain't allowed in school !

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    • #3
      Originally posted by loudthud View Post
      Is there a Master Volume between the tone stack and V4 ?

      R15 seems like a good place to insert a Master Vol, but it makes me wonder if low drive to V3 in the High Channel mode might make it sound restricted.

      Isn't what is really wanted is two Masters between the tone stack and V4 ? What circuitry is connect to CON9 ? Effects Loop ?
      thanks for that
      yes there is a master vol but that is for both high and low drive. the problem is if you set you levels up for low drive and get them where you want, if you switch to high drive its too loud with the only option of adjusting the amp or rolling off the guitar vol to get the desired level
      I believe im right in saying that signal out of v3 going to the tone stack is either Low or High so adding a master there would work but wont be able to select just high channel , which is the desired effect ... Yes ??
      thanks
      Mr A

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      • #4
        What I'm suggesting is using a DPDT relay to switch between two Master Volume pots. The relay would be activated at the same time as RL2 so one MV is for the "Clean" Channel, the other for the "High Gain" Channel.

        Edit: Hold on a minute. There is no Master on Con9, the Master is after the PI. Wish I could see a complete schematic. That makes adding a second Master the way I envisioned it kind of impractical because you would need two DPDT relays. Still I think adding a Master at R15 won't be satisfactory because it just turns down the overdrive.
        Last edited by loudthud; 11-25-2021, 11:31 PM.
        WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
        REMEMBER: Everybody knows that smokin' ain't allowed in school !

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        • #5
          I think it may be feasible to fit a second Type1 master, and use a DPDT relay to flip the output valve grids from one pair of wipers to the other.
          As the tracks are 1M, I can’t envisage that a second track in parallel per side will cause a problem.
          My band:- http://www.youtube.com/user/RedwingBand

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          • #6
            Here is the complete schematic.
            Attached Files

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            • #7
              The way I see it, R14 and R15 are basically functioning as a 1M pot set at half. So playing with those values or changing to a pot would be simple. But it would alter the distortion character as has been noted.
              Some have reported that putting a low gain tube such as 12AU7 in V2 position makes up most of the difference. That would be the quickest and cheapest, but again may affect the distortion character.
              "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

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