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  • Heater wire routing question

    Hi
    I recently saw a video of Gerald Weber online somewhere. He was working on an old Fender twin Reverb. He mentioned that the twisted sections of heater wires were routed incorrectly, and that you should have the heaters running from say pin 2, to the next valve's pin 2 and not to its pin 7 (6l6), etc
    Same thing goes for the 12AX7's. All the pin 4's should be linked and all pin 5's.
    What truth lies in this?
    What difference does it make?

  • #2
    He is trying to keep the heaters in phase?
    That would explain why Fender (and everyone else) used the same colour wire for both sides of the heaters, just to screw everyone up Click image for larger version

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    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


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    • #3
      For p-p power tubes, there's a theoretical benefit that heater hum, being common mode if there's consistent heater polarity, may tend to cancel out. It seems like good practice so might as well do it like that as not.
      With pre-amp tubes, each cascading stage flips signal polarity, so there's a hypothetical scenario in which particular control settings and maintaining heater polarity may result in heater hum being lowered. However, my take is that by the same token, different control setting may result in heater hum being increased with consistent heater polarity, so don't see that it matters.
      Good lead dress may have far greater benefit in minimising the heater circuit producing interference in the signal circuit..
      My band:- http://www.youtube.com/user/RedwingBand

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      • #4
        Exactly, keeping the heater wires away from signal wires as much as possible, and try to have signal wires cross heater wires at 90 degree angles as much as possible, that will have a far greater benefit than worrying about heater phase.

        Power tubes are the least sensitive to heater hum of all the tubes in an amp. So if it pleases the anal in you, make all the 2s and 7s work together. Hey, I am anal about making all my resistor color codes read th same direction on the part board. Probably has about as much hum improvement as phasing the heaters.

        In the preamp, I couldn't imagine spending hours trying to figure out the signal inversions and the required heater phasing at each tube to minimized hum. At best it would be that last half a percent or something I need to take the Nobel Prize for tube amps.
        Education is what you're left with after you have forgotten what you have learned.

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        • #5
          Exactly, keeping the heater wires away from signal wires as much as possible, and try to have signal wires cross heater wires at 90 degree angles as much as possible, that will have a far greater benefit than worrying about heater phase.

          Power tubes are the least sensitive to heater hum of all the tubes in an amp. So if it pleases the anal in you, make all the 2s and 7s work together. Hey, I am anal about making all my resistor color codes read th same direction on the part board. Probably has about as much hum improvement as phasing the heaters.

          In the preamp, I couldn't imagine spending hours trying to figure out the signal inversions and the required heater phasing at each tube to minimized hum. At best it would be that last half a percent or something I need to take the Nobel Prize for tube amps.
          Education is what you're left with after you have forgotten what you have learned.

          Comment

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