12AU7 tube variations and Cinch tube shields | The Canadian Guitar Forum

12AU7 tube variations and Cinch tube shields

Discussion in 'Amp Building/Technical/Repair' started by Hammerhands, Oct 19, 2019.

  1. Hammerhands

    Hammerhands

    Joined:
    Dec 19, 2016
    Location:
    Winnipeg
    I was doing some long overdue testing on a tube distortion unit. There isn’t a lot of space in the unit and they had these Cinch tube shields on the tubes that look a lot like this:

    [​IMG]

    They fit snuggly on the socket, they have some kind of array of metal prongs that grab the tube very tightly inside. These are actually a punched sheet of spring metal that is stuffed in there.

    To put the shields on one of the tubes in the unit, you would need to place the shield on the tube, put the tube in place in the socket, plug the tube into the socket by pushing on the tube through the top of the shield before seating the tube shield.

    I found this impossible. Am I missing something?
     
    Last edited: Oct 19, 2019
  2. Hammerhands

    Hammerhands

    Joined:
    Dec 19, 2016
    Location:
    Winnipeg
    This post TL/DR

    Cliff Notes: Can something make a tube cut out or short out when it is pushed?


    I own three of these distortion units, each one sounded different or had a different issue.

    When I got the original one, I noticed that if I had it all the way up with quite a bit of bass and I was playing a chug, chug, chug power chord, it would sometimes cut out for a few milliseconds. It sort of sounded like I was picking the chord an extra time.

    I took it back to the creator and he said, “I didn’t think anyone would ever use that much bass.” He gave me a new unit a few weeks later, he said he added bigger capacitors, which made sense to me, it had been using up all the power and was bottoming out.

    A few years later I bought second unit that made the same noise. A few years later, I bought the third unit and it didn’t have as much gain as the other units.

    I took them all to a tech and asked him to try to get them to be like the first unit. I told him about the bigger capacitors. I got them back and not much seemed to change. He fixed some lurking issues and noise problems, but the second one still had the skip and the third one still had less drive.

    I looked at the filter capacitors tonight and they are all the same. I think I remember him saying there wasn’t any difference, that he hadn’t needed to do anything. Which makes me wonder if some other capacitor had originally been changed.

    Tonight I put different tubes in them. The first one has a JJ on the left and a Electro-Harmonix on the right, the second one had two JJs and the third one had two NOS tubes of various types. I got two Electro-Harmonix tubes a few months ago and I put one in the right side of the second and put that JJ in the third unit with the other new tube.

    So now they have the same tubes. I need to properly A/B/C them they do sound more similar now. I think the JJ in the third unit needs to be changed out.

    I can imagine how the different tubes would vary in gain, but what would cause that skipping sound?
     
    Last edited: Oct 19, 2019
  3. DaddyDog

    DaddyDog Gold Member

    Joined:
    Apr 21, 2017
    Location:
    Mississauga, ON
    I’ve never heard of an issue like that. Interested to hear if you solve it.
     
  4. jb welder

    jb welder

    Joined:
    Sep 13, 2010
    Location:
    Melonville, Canada
    The tube is supposed to go in first, then the shield goes on. Is there not room for this?
    If not, I guess they did it somehow during assembly of the unit, and too bad for anyone who has to deal with it later.
     
  5. Hammerhands

    Hammerhands

    Joined:
    Dec 19, 2016
    Location:
    Winnipeg
    When I bought #2 it had the shield in place, and I think the original one I had did as well, the other 2 did not.

    I asked the tech if he had more shields and he was able to get them on #1 and #2 somehow. He’s a wizard?

    They work fine without the shield.
     
  6. Hammerhands

    Hammerhands

    Joined:
    Dec 19, 2016
    Location:
    Winnipeg
    They all sound the similar now and I heard no skipping.

    I realized that the first one has always had a wonky gain pot. It doesn’t go up smoothly like the other two, it has a couple of abrupt jumps. I’m not sure if I will do anything about that.

    I originally bought the second one so I could have two distortion sounds ready to go, and then I found that it worked great as a clean boost into the first one when using a Telecaster.

    What do all three sound like? It’s a wall of noise but not completely unmusical, with little whistles that sound like resistors frying or electronic feedback, so I don’t need to do that again! Or maybe if you set the EQs a bit differently...
     

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