Home › Forums › Vintage EHX › Russian Muff – Power Supply Mod Grounding Question

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  • June 21, 2010 at 4:16 pm #80388
    alex192
    Participant

    Hi guys!

    I am currently trying to modify my Black Russian Big Muff (I believe it is an early black version as it comes with the larger 6 screw box and hole for the larger, old style footswitch).

    I want to add a 9 volt 2.1mm jack into the shell (between the input / output) so that I can daisy chain off my mains power supply. However, I have a few questions before I ruin the circuit by wiring it incorrectly:

    1. I believe the Russian Muffs are postive ground. I want to wire the 9 volt socket (which is all metal shell; no plastic insulation for the outer sleeve) into the shell and wire it so that it is centre negative. I have read in various places that for some applications the 9volt socket needs to be isolated from the case. Do I need to do this if I am wiring the socket as centre negative (outside barrel is postive) and it is postive ground (shell is postive)?

    2. Is the postive ground going to be a an issue when daisy chaining it with other pedals which are negative ground? As long as I have all the sockets as centre negative, does this then mean that I can daisy chain, or would I need a seperate islotad supply for anything which isn’t negative ground (aka Big Muff)?

    Cheers!!

    June 21, 2010 at 4:23 pm #109662
    The EH Man
    Moderator

    First off, I don’t recommend wiring it as a positive ground pedal. It will interfere with powering your other pedals from the same supply.

    I add DC jacks to these fairly often. Purchase a plastic bodied jack so you can have a safe negative ground pedal with a center negative jack.

    Once you get the jack installed, add a new 9v clip then cut the clip off the original clip and attach those wires to the DC jack. That’s all there is to it.

    June 21, 2010 at 4:28 pm #109664
    alex192
    Participant

    From my understanding it is postive ground to begin with. That is where my main worries come from. Is it a simple task to switch between psotive and negative ground for a pedal?

    Thanks for the quick response!

    June 21, 2010 at 4:31 pm #109665
    The EH Man
    Moderator

    No, negative ground is the stock configuration.

    June 21, 2010 at 4:35 pm #109667
    alex192
    Participant

    Ah, thanks very much for the reply! I thought I read somewhere that these Russians are negative ground. They were obviously wrong!

    June 21, 2010 at 4:37 pm #109668
    The EH Man
    Moderator
    Quote:
    Ah, thanks very much for the reply! I thought I read somewhere that these Russians are negative ground. They were obviously wrong!

    No, they’re right. It is negative ground.

    June 21, 2010 at 4:49 pm #109670
    alex192
    Participant

    Sorry, my mistake! I meant to say

    ‘I read somewhere that these Russians are postive ground. They were obviously wrong!’

    For future reference, if a circuit is postive ground (chassis is postive) and the outer part of the socket is also postive, does it matter if they touch? In other words, do you only need to isolate the socket if the outer sleeve is a different polarity to the grounding in the case?

    June 21, 2010 at 5:30 pm #109671
    The EH Man
    Moderator

    Isolate only if different. I would still recommend getting the correct jack.

    June 21, 2010 at 9:40 pm #109688
    alex192
    Participant

    Thanks a lot for the help. I’ve ordered a new socket with insulation, and a 3pdt switch while I was at it. Cheers for the help!

    June 21, 2010 at 9:53 pm #109693
    The EH Man
    Moderator

    If you need more help, we’re here.

    June 22, 2010 at 1:42 pm #109723
    burnthogan
    Participant

    I was thinking of doing this to my muff since I already have had to tinker with it. I have three semi-related question that you guys might be able to help me out with.

    1. Where’s a good place on the web to source parts like the new socket with insulation, and a 3pdt switch?

    2. What rating soldering iron / size tip is best for working on pedals?

    3. What kind of solder do you use?

    Thanks

    June 22, 2010 at 2:00 pm #109724
    The EH Man
    Moderator
    Quote:
    I was thinking of doing this to my muff since I already have had to tinker with it. I have three semi-related question that you guys might be able to help me out with.

    1. Where’s a good place on the web to source parts like the new socket with insulation, and a 3pdt switch?

    2. What rating soldering iron / size tip is best for working on pedals?

    3. What kind of solder do you use?

    Thanks

    1) Small Bear Electronics or Pedal Parts Plus

    2) 15 – 20 watts is fine for most applications

    3) rosin core, small diameter.

    June 22, 2010 at 2:57 pm #109725
    burnthogan
    Participant

    Ron,
    Your responses have been invaluable to me. Thanks.

    June 29, 2010 at 6:33 pm #109889
    burnthogan
    Participant

    I just added the power supply last night and it works like a champ. I was suprised how easy it was. It only took me about a hour; because I was really taking my time. Now I can power my muff right off my pedal board or via the 9volt battery. Now I’m considering adding a true bypass switch to it.

    June 29, 2010 at 8:40 pm #109892
    alex192
    Participant

    While we’re on the subject, I just rewired the 3pdt switch and it is all working very well. However, I get a slighy popping from when the switch is operated, when the LED pulls current when being turned on. There are two solutions:

    1) Add a cap and reistor: http://www.muzique.com/lab/led.htm

    2) Rewire so that it is always grounded http://www.dazatronyx.com/support/true-bypass-technique.pdf (bottom right)

    Which would you say is the ‘proper’ way of doing it?

    Cheers”

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