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  1. S

    4ohm amp through a 8ohm speaker?

    Nop not a very safe situation, this will put strain on your OT, you could run into an OT failure eventually, maybe not also, depends. The other way around is safe ex: 8 ohms from the amp to a 16 ohms cab for instance is safe, the ot will run colder even, gives a break to the amp!!!... You...
  2. S

    Selling a Marshall

    :shock: :roll:
  3. S

    How to add the effect loop to Marshall 1987

    Check your PM (messages....) :wink:
  4. S

    How to add the effect loop to Marshall 1987

    Hold on I'll help you out........I have a loop diagram somewhere Cheers, JF
  5. S

    Who's using a variac?

    The 450vsc on the plates are the manufacterer recomandations (Siemen) specs....all el34 are rated at 25watts and you want to bias them around 60-70% of that.......
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    Who's using a variac?

    Re: Stepdown tranny Just check your heaters voltages, at 115v you should be ok, but just in case, if your below 5.7/5.8, I'd increase the wall voltage till you have at least that minimum or your tubes won't have a long life, at 5.5 they won't last a month, below that they won't last a...
  7. S

    Master volume in my '71 SB

    Really? Like where???
  8. S

    Master volume in my '71 SB

    Great, let me know how you like it!! There is other ways also.........
  9. S

    Master volume in my '71 SB

    here is one exemple I found for it: http://www.putfile.com/pic.php?img=3953067
  10. S

    Master volume in my '71 SB

    I have probably the most dynamic MV for you, BUT there is many other ways to do them..... You'll have to try and see which you prefer... here it goes: 1) get a dual 250k audio pot (24mm alpha are way ok for this) 2) two 2.2Mohms 1/4w resistors 3) Some shield wire and regular 22gauge...
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    Full Blown Buzz

    Blue like a propane flame on a BBQ, at the base of the flame you see the blue color, like that....Check them in the dark, the heaters will also glow orange, all the time of course.... The inner part of the tube will have the blue glow AND when you play the amp it will have variation of the...
  12. S

    JCM900 with power brake

    Don't try to play your amp with only one tube......this won't work and will damage your OT (for a 50w)
  13. S

    JCM900 with power brake

    Nothing is connected on your pic??!! Normally in mono one jack is needed and both speakers will play, just stick in the proper mono jack input..For stereo you'll need two jacks in the cab normally, and you must put the selector on stereo at the cab...I can't see on your pic...... -If you...
  14. S

    Harma & Philips

    Use the 5751 tube in V3, way enough, as for the others, well it depends if you like it or not, I'd go strait with 12ax7/ECC83.........as for the power ones fairly good!! But at the end, you like the amp? Stay like that!!! 8) :wink:
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    JCM900 with power brake

    No no no......... When you pull two tubes your amp output impedance changes to a higher value automaticly, you have to correct that mismatched by lowering the impedance selector one step lower (ex. if at 16ohms go 8ohms, if at 8ohms, go 4ohms.....), you will have haft the power in all cases...
  16. S

    JCM900 with power brake

    You will lose headroom but it still will be loud, less a little but loud still... Good luck!
  17. S

    What is Gain?

    .....to concluse on what is GAIN......... SETTING PROPER GAIN STRUCTURE: One of the most overlooked yet most important things in a typical band's PA system is gain structure. Gain structure is the practice of matching the levels throughout your system so that: 1) Each device in the...
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    What is Gain?

    In a different view/more "tube amp" oriented simplified version, here are some basic info on gain, etc... As you will see gain and distortion ain't the same thing but works togheter..... Overdrive: Used to be called Distortion but that isn't descriptive enough. It is the idea of using one...
  19. S

    What is Gain?

    You know, too often I see lots of guys that have the misconception that gain=volume, when this is simply not the case. You will spot these guys as they tend to set the volume of each channel with the gain pots instead of the channel faders. Gain in a live PA is signal strength. A microphone...


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