Output transformer question

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Rob F, Feb 15, 2008.


  1. Rob F

    Rob F Member

    Messages:
    5
    Joined:
    Dec 20, 2007
    Are output transformers for push/pull amps sthe same as output transformers for single ended amps?

    This is what I have going on...

    I have two chassis I pulled from old HiFi systems. Each run (4) 6v6s. They each have two output transformers for the stereo. The first one (Voice of Music brand) has a two output transformers and a push pull Power transformer which I plan to use for my first build and only use half of it to make a 5E3. The second one (Magnavox brand) has a single ended PT with two output transformers that seem to branch off in a "Y" so-to-speak to make it a stereo output. This one seems to be a much simpler design so I may use it to try the 5E3x2 stereo for my next build.

    Basically....Can I use the OT from the Push/Pull chassis in a single ended design? Let me know what you guys think.
     
  2. phsyconoodler

    phsyconoodler Member

    Messages:
    4,352
    Joined:
    Jul 11, 2005
    Location:
    calgary canada
    Ok,first of all,a power transformer is not classified as push pull or single ended.It only supplies power and current handling capabilities.An output transformer is classified that way,and you can tell by the number of wires.It has two wires that go to the plates of the power tubes and a centre tap that goes to a high voltage connection,usually a screen supply that is filtered DC.
    You can use a push pull OT on a single ended amp,but it is not recommended because a single ended OT needs to have a larger core gap to handle the current.A single ended amp is conducting current all the time,so it needs to be able to handle the demand placed on it.A push pull OT is handling current half the time so it can have a smaller core gap.
    If you use the push pull OT,make sure it has at least a 20 watt rating for a 5 watt single ended amp.
     
  3. jh45gun

    jh45gun Member

    Messages:
    409
    Joined:
    Dec 29, 2006
    So then your saying a SE transformer would only have one wire that goes to the plate of the power tube and one that goes to the High Voltage? I asked Rob to post this as I have a friend that has a RCA chassis he wants to do something with and it has a couple of OT's on them and I wondered if they were SE transformers used on a stereo setup and I wondered what an easy way to tell was. Another thing how do you tell the wattage of an OT that you may find on an old chassis? Any easy way?
     
  4. Swarty

    Swarty Member

    Messages:
    1,143
    Joined:
    Dec 16, 2003
    Location:
    Michigan
    Many SE hi fi output transformers have a screen tap which means they have the same # of wires as a push pull OT (and often the same red, blue, brown colors).
     
  5. Rob F

    Rob F Member

    Messages:
    5
    Joined:
    Dec 20, 2007
    Seems all of the OTs on both of my chassis have the same amount of wires coming from them.
     
  6. jh45gun

    jh45gun Member

    Messages:
    409
    Joined:
    Dec 29, 2006
    OK so any good way of telling whats what if you do not have a schematic?
     

Share This Page