MC10 Nearing Completion

Discussion in 'Shock Brother's DIY Amps' started by andrewRneumann, Jul 30, 2020.

  1. andrewRneumann

    andrewRneumann Tele-Meister

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    Update!

    I finally made some decisions and settled on final values for various circuits in the MC10.


    When you've got so many options, it's overwhelming. I've got some thick callouses on my playing fingers. Haven't had that since my college days!


    Some of the more drastic changes I made to the original design:

    1. Changed target bias settings for 2nd through 4th stages from Cold-Hot-Cold to Hot-Cold-Hot.
    2. Removed cathode bypass from 2nd stage.
    3. Add switchable cathode bypass to 3rd stage.
    4. Added a choke to the power supply.
    5. Incorporated a low-impedance attenuator on the 3rd stage load resistor that feeds the tone stack and 4th stage. This avoids an extra voltage divider after the tone stack and the issues associated with that design.



    I just got my Presonus iTwo in the mail. I'll be hooking the MC10 up to my Mesa Studio 1x12 cabinet and making some recordings. I'm going to smother the cabinet in moving blankets with a Rode NT2 I've had in storage for years. Crank it up!

    Thanks everyone who's taken an interest so far and thanks for putting up with all my questions! This is a fine group of people.
     
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  2. James Knox

    James Knox Tele-Meister Ad Free Member

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    She’s a beaut...
     
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  3. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    Do you have an accompanying schematic?
     
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  4. andrewRneumann

    andrewRneumann Tele-Meister

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    And here's the schematic as it stands...

    MC10.png
     
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  5. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    I like all the 'new' solutions. More evolution in this one amp than in Fenders and Marshalls the last 60 years.

    ... Except the standby switch :)

    I would recommend a humdinger. You can dial out hum very precisely.
     
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  6. andrewRneumann

    andrewRneumann Tele-Meister

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    After spending hours making small changes to the amp, I am actually quite happy to have the standby switch. With the solid state rectifier, I can easily blow a fuse with too many “on” “off” cycles. I got into a routine when testing and modifying—play, power “off”, drain caps, modify, power “on”. I could probably do the whole cycle in 30 seconds if I was doing something easy to change... one alligator clip here or there. I found if I went too fast and didn’t spend a few moments in standby, eventually I would blow the fuse. The amp only draws 200mA at 120VAC, so I feel like a 0.5A fuse is appropriate. I guess I could put in a 1A fuse for testing and then back it back down to 0.5A when all the fooling around is over.

    You are right about the humdinger. My next build I’m going to do that and also elevate the heaters. Truth be told the 60Hz I’m getting isn’t very much and only at high gain, high master volumes do I even notice it at all.
     
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