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  • #1

    Amp Switch

    Ok, let's start with "I am a rank amateur regarding pedal design and don't know what I'm doing." That's why I would appreciate some help.

    I'm getting ready to build a pedal board, and I'm tired of pulling out & re-connecting the cables needed to switch between my Blues Jr. (no effects loop) and my TradeMark 10 (effects loop). The following is my first attempt at an A/B box to switch between the amps.



    I don't play live and don't need on-the-run switching. Also, it's only one amp or the other, not both.

    Soooo...

    Do I need the fourth switch for lifting the ground(s) of the amp that's "off" (blue lines)? It seemed like a good idea at the time.

    Is a 1 meg resistor OK for the input lines? This is intended to help eliminate "popping" when switching.

    I've seen buffered circuits for amp switching, but they seem to always involve A/B/Y switching. Do I risk damage to my amps (or myself) without a buffer circuit in here? Looking at this again, it seems like turning the switch with both amps on would be just like pulling out the guitar cord - not necessarily good. How about a BIG resistor between the lifted ground and ground? I could just make sure both amps are OFF before switching, but we all make mistakes...

    BTW - Mouser has a cheap rotary 4-pole/double-throw switch that I can use instead of a typical stomp box switch, and with a chicken-head knob I don't need any LED indicator(s).

    Thanks in advance for any and all assistance.

    Chip
    Heritage 535 Special, Warmoth frankenstrat, MIM Strat, & Taylor 314C(no E)
    Amp Builds: Tweed Princeton (5F2-A) variation, 2 BF Princeton Reverb clones, & Super Reverb clone
    Sometimes use a Blues Jr., Tech 21 Trademark 10 & Power Engine 60
    SPG modded DS-1, TS-7 & CryBaby; Visual Sounds Rte. 66 & H2O; Guyatone Tremolo
    SD pickups: SSL-2, APS-2, tapped Quarter Pound, Custom 5 & Antiquity humbuckers

    "Conan! What are the best things in life?"
    "Girls, guitars, guns and cars!"
    Tags: None
  • #2
    Re: Amp Switch

    ill look at it later. ill let ya know.
    Jeremy Ledford
    Tone Guru Extroardinaire
    Tone Shop

    Comment

    • #3
      Re: Amp Switch

      OK still unsure, but I've crawled around the web some more, including Aaron's Stomp Box Forum, GeoFX, etc. Got some other ideas, tried a couple...

      Decided that "pull down" resistors on the input from 1st effects chain and input from the 2nd effects chain might not make much sense since they are always in the circuit.

      The first diagram above lifts the grounds from jacks when they are "off" (out of the circuit). In this second alternative, the fourth pole of the switch grounds either the TM-10 or Blues Jr. positive input jack (tip) through a big resistor (maybe 2 meg?) when the other amp is selected. The only "pull down resistor" is on the input from the TM-10's effects loop "Send" since that pole of the switch doesn't go anywhere when the Blues Jr. is selected.



      Is this better, worse, or still stupid? (Please don't answer the last part )

      I thought about grounding the positive tips of the jacks for the effects loop send & return with another switch pole, but it would actually take two more poles because I can't link the TM-10's input, Send or Return directly. There is a 6-pole, double throw switch if grounding those tips when not in use would be better.

      Chip
      Heritage 535 Special, Warmoth frankenstrat, MIM Strat, & Taylor 314C(no E)
      Amp Builds: Tweed Princeton (5F2-A) variation, 2 BF Princeton Reverb clones, & Super Reverb clone
      Sometimes use a Blues Jr., Tech 21 Trademark 10 & Power Engine 60
      SPG modded DS-1, TS-7 & CryBaby; Visual Sounds Rte. 66 & H2O; Guyatone Tremolo
      SD pickups: SSL-2, APS-2, tapped Quarter Pound, Custom 5 & Antiquity humbuckers

      "Conan! What are the best things in life?"
      "Girls, guitars, guns and cars!"

      Comment

      • #4
        Re: Amp Switch

        OK - one shameless bump just in case somebody can help out...

        A couple guys on Aaron's Stompbox Forum gave me more things to think about, including this circuit: http://www.geofex.com/FX_images/spltr2.gif.

        Frankly, I'm beginning to think that I should either (a) keep it totally simple and just make sure both amps are always turned off before touching the box, or (b) punt and pick some pedals for the Blues Jr. and use others for the TM-10.

        Those buffered, isolated circuits look like black holes for tone to my un-educated eyes.

        Chip
        Heritage 535 Special, Warmoth frankenstrat, MIM Strat, & Taylor 314C(no E)
        Amp Builds: Tweed Princeton (5F2-A) variation, 2 BF Princeton Reverb clones, & Super Reverb clone
        Sometimes use a Blues Jr., Tech 21 Trademark 10 & Power Engine 60
        SPG modded DS-1, TS-7 & CryBaby; Visual Sounds Rte. 66 & H2O; Guyatone Tremolo
        SD pickups: SSL-2, APS-2, tapped Quarter Pound, Custom 5 & Antiquity humbuckers

        "Conan! What are the best things in life?"
        "Girls, guitars, guns and cars!"

        Comment

        • #5
          Re: Amp Switch

          i wouldnt worry too much about the buffer circuits. rg designs up some whip daddy toys.
          Jeremy Ledford
          Tone Guru Extroardinaire
          Tone Shop

          Comment

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