Pre amp tube layout in Randall RD100?

Discussion in 'Gear & Equipment' started by Vrollin, Mar 13, 2015.

  1. Vrollin

    Vrollin SS.org Regular

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    Wanting to swap in some different brands of pre amp tubes in my RD100 to see what effect it has, looking at tung sol over the stock rubys, however I am unsure which of the 12AX7's relate to which feature on the amp. Im mainly just wanting to swap out the tubes that effect the dirty channels and the clean channel sounds great as it is, unless of course better tubes would improve it too.
    Can anyone shed some light on which tubes relate to the gain channels?

    Thanks!
     
  2. jarnozz

    jarnozz Let´s Get Wasted!

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    v1 is for the input stage and the first stage of the clean channel. don't go with a high gain tube here. A mullard would be nice here. the last valve is the phase invertor. an lps sovtek does wonders in this stage. the rest of the tubes are probebly for the gain channels so try out some and keep those you like most :)

    try swaping all preamp tubes except the first and last. I think the last one was labeled PI.
    tung sol's are way better than ruby's in my opinion
     
  3. Vrollin

    Vrollin SS.org Regular

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    Will it generally have a label on the tube socket? Im really unsure as to which one will be first and last as I have seen people say it goes from left to right and others say it goes from right to left.
    Also there is one right next to what i am assuming is the invertor? Is it safe to say this would be the invertor tube?
     
  4. jarnozz

    jarnozz Let´s Get Wasted!

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    I'm afraid not. I found no schematics online and the best thing you can do is search for it on the web. you could post your question on randalls fb page or email them!
    Opening up your amp is not the smartest idea if you have no knowledge about amps, technical knowledge that is.
     
  5. Vrollin

    Vrollin SS.org Regular

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    Ok so from Randall I have got the following info:

    V1 is Clean (V1 is closest to the input jack)
    V2 is Overdrive
    V3 is second stage Overdrive (V3 is closest to the phase inverter)
    V4 is phase inverter

    So from this my understanding of the tube layout is this. The three in the front and closest to the jack are preamp tubes and the one towards the back but near the input is PI?
    [​IMG]
     
  6. UV7BK4LIFE

    UV7BK4LIFE Schecter A7 addict

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    Yes, this is correct
     
  7. Vrollin

    Vrollin SS.org Regular

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    Win! Have the Sovtek LPS and 2 tungsols on the way! So keen to see how it is all effected by it, from reading around on the web the Sovtek LPS is a big deal in use with phase inverters!
     
  8. p4vl

    p4vl SS.org Regular

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    Some folks use NOS tubes in v1 (like me). I have a $30 RFT 12ax7 that I got from Russia that really helps for a more '3D' sound (hard to describe). Old NOS tubes are especially useful in amps that basically have more gain on tap than you'll ever need.
     
  9. Vrollin

    Vrollin SS.org Regular

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    Going to ask a really noob question here, I thought I knew a little more about tube amps than I do after reading around about various things, when you select say the second channel, is the signal passing through V1 and then V2, so its adding more gain from each tube on the way? And then the third channel is running V1, V2 then V3? I was of the understanding that one tube was for one channel alone, but reading around it makes it sound like it goes through each one, or have I completely misunderstood this?
     

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