Reply to Thread Bookmark Thread
Page 2 of 2 FirstFirst 12
Posts 51 to 56 of 56
  1. #51

    User Info Menu

    KCA NOS Tubes has always been a good source for NOS stuff.


    The Jazz Guitar Chord Dictionary
  3. #52

    User Info Menu

    TAD makes a nice 6SL7!

  4. #53

    User Info Menu

    Okay, so I need some help concerning my octal project.

    As a student I'm on a tight budget, but still i want to get into octal territory. I have this old Tube overdrive Pedal (Behringer VT-999) which I rarely use. Basicaly It's an external Tube preamp using a 12ax7.
    I bought an 9pin to octal Adapter, and wanted to replace the 12ax7 with a 6SL7, what (according to a lot of forums I've been digging through) should work.

    Yesterday I got around to testing it and it didn't do anything at all.
    With the octal Tube plugged in Not even the Power LED of the Pedal will light up. When i switch back to the 12ax7, everything is fine.

    Anybody got an idea what I'm doing wrong?

  5. #54

    User Info Menu

    Most adapters, I should imagine, are designed with the idea that you will be replacing a 9-pin _power_ tube (e.g., the el84) with a 6V6gt. As such, the wiring for the adapter is probably going to accommodate that.You are using the adapter for a different concept, i.e., to sub an octal preamp tube for a 9-pin preamp tube--the 6sl7 for the 12ax7. Two things to keep in mind: (1) both tubes are preamp tubes, (2) the 12ax7 is a dual triode tube in a single glass case, the 6sl7 is a single triode tube in a glass case. From (1) if the Behringer preamp is using only one of the 12ax7 triodes you are in like Flynn. If, on the other hand, the Behringer is employing both triodes, you will need two octal tubes to get the job done.

  6. #55

    User Info Menu

    Continuing: if the Behringer is using a single triode in the 12ax7, all you will likely need to do is to carefully rewire the adapter to make it a preamp tube adapter, not a power tube adapter (if I am correct in my assessment).

  7. #56

    User Info Menu

    Thanks a lot for the elaborate answer Greentone!

    The adapter I bought is actually specifially designed for substituting a 12ax7 with a 6sn7, so I think that isn't causing the problem.
    I looked up some wiring schematics of the behringer and i think it is actually using both triodes... Although I'm not to savvy about electronics to be true. So I might be misreading those schematics.

    There's one thing i find interesting though: when i Power the Pedal without a Tube it turns on and all the LEDs Light up as they should. But as soon as I plug in the adapter everything turns off.

    Guess it doesn't work out then. At least I learned something along the way ?