Carvin DCA 800, only NPN?

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cm961

cm961

Member
2001-06-14 3:17 am
Peterborough, Ontario
  • #1
    Hey guys,

    I just bought a non-working Carvin DCA 800 from ebay. Anyways, its a really neat amp. One channel has like no gain, pretty much what goes in comes out, and the other channel blows the fuse. I measured the resistance between the +ve supply and ground on the amp channel and it was only 30 ohms or so, easy to see why the fuse blows.

    I'm getting somewhere with these boards, but I have a big question. I'm familiar with class A, class B, or at least I like to think so. Now these amp channels each use 6 MJ15003 transistors per channel... That is, they're all NPN. So does this mean the amplifier doesn't use a complementary pair?!? Isn't that strange? Can someone point me to some schematics of amps using non-complementary pairs so I can inspect them.

    Any help would be great guys!

    Pete:bigeyes:
     
    cm961

    cm961

    Member
    2001-06-14 3:17 am
    Peterborough, Ontario
  • #2
    Hey again,

    I just wanted to add a few things. I was looking in Randy Slone's book (High power audio amplifier construction manual) (my bible). And out of list of availible output stages, I'd have to say this must be class A single ended. Is there such thing as class B single ended? I really doubt it since it would only output half the signal! Is there such thing as a push/pull (complementary) stage (of whatever class!) using all the same transistor? I don't think so. Man this is a tough one.

    Pete
     
    T

    ThingyNess

    Member
    2002-02-09 7:36 am
    Vancouver, BC, Canada
  • #3
    If you have Slone's book - have a look at his diagrams for the BJT Quasi-Complementary output stage.

    Your OPS most likely has a PNP driving an NPN (Complementary feedback pair) and an NPN driving an NPN (Emitter follower, full darlington connection) on the opposite rail.

    It is indeed possible to have a push-pull class B output stage with only NPN transistors.

    Consider the fact that tubes only come in "N" type devices, and they've had push-pull class B tube output stages since before I was alive. :)
     
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