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Thread: Fully Discrete 400 / 700 Driver Circuit (Full Comp Only)

  1. #11
    Forum Veteran grapplesaw's Avatar
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    Quote Originally Posted by krellmk View Post
    Isn't this design similar to the Leach Super amp and the Low tim amp?
    The Leach is a double barrel design. Compare the attached with THD+N's design and you will see a vast difference

    go here to get image below in a clear the PDF https://leachlegacy.ece.gatech.edu/superamp/circuit.pdf
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by grapplesaw; 07-23-2017 at 01:32 AM.
    try the Lightening Bolt WOPL 1000 for a hair lifting experience today

    Warning !!! Use only when you want to blown the town down

    proud father of the only WOPL Fully Comp dual 500

  2. #12
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    The Leach DB design used stacked output transistors to increase power output. The "stacking" (a variation of cascoding) also allowed the use of transistors with a lower voltage rating.

    However, to answer your question, the design I am working on is not the same as the Leach. The Leach design does not use any current mirrors in the input stage nor is the VAS buffered with an emitter follower.

    I've never heard a Leach Amp, but I understand they sound very good. I have a few AB International 600LX's, which are similar to the Leach, and the 600LX sounds pretty good.

    I'm not really a MOSFET person. I've tinkered with a few basic designs, but always come back to BJT's.

  3. #13
    New Around These Parts krellmk's Avatar
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    Are you satisfied with the life you're living

    Fully Discrete 400

    Keep me posted when the boards are ready

  4. #14
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    Quote Originally Posted by Northwinds View Post
    Is a major overhaul needed with an already made WOPL (out of curiosity)
    My intention is to make the new PCB the same dimensions as the original PL36 board with connections at the bottom. The only modification will be to the 150 Ohm pre-driver and 10 Ohm driver resistors.

    The 150 Ohm resistors can be removed because the new PCB will include the pre-driver resistor (one resistor is shared between the 2 pre-drivers). The two 10 Ohm resistors can be replaced by two 18 Ohm resistors or a single 36 Ohm resistor.

  5. #15
    Forum Veteran Gibsonian's Avatar
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    I'd be interested in trying this out on a spare PL700 series I have just sitting there on the shelf. Please keep us posted.

  6. #16
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    After tossing the new amp idea around for awhile and considering the 400 and 700 chassis layout, I have finalized the amp design. It's not the one I was anticipating originally, but it is a good design (tried and true) and should offer exceptional performance from a 400 or 700 chassis.

    The amp design is a classic Lin topology with current mirrors. I have added a cascode to the input stage, so I can experiment with different low noise input transistors. The VAS is buffered from the input stage as well as sharing the current source. A lot of decoupling has been implemented so the triple emitter follower (EF3) is stable with no tendency to oscillate. Because of the way the current source is configured, there should be no turn-on/off thumb or pops.

    See schematic and layout below;



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    I am proofing the layout now, and hopefully, I'll have some boards ready for testing soon.

  7. #17
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    Nick,

    I would like to talk to you some more about this.

    Please PM me your phone number.

    Ed

  8. #18
    Forum Veteran WOPL Sniffer's Avatar
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    Screw it
    Don't do it Nick, you'll never get off the phone..... LOL

    No, seriously, I'd like to do some playing... let me know when they are available,and price. These will fit into a 700B/II chassis and its all 1 board?.... you ginned em up just like that and will bolt right in? I'm impressed. Sometimes I'm loaded, but right now, I'm impressed.
    I had the nations problems figured out one night while on blah blah blah........ huh?

    Big amps
    Kenner Close N Play

  9. #19
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    The new PLX driver board is slightly larger than the original PL36. The PLX is 8.25" x 5.75". The original Pl36 is about 6 3/4" x 5 5/8".

    The PLX will fit into 400 and 700 chassis, but I'll have to double check fitting both the PLX and a DCP. I just thought about how popular the DCP is just now.

    The PLX is all one board.

  10. #20
    Forum Veteran WOPL Sniffer's Avatar
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    Screw it
    I got a couple of your other control boards i was gonna try this winter on couple mono's.
    I had the nations problems figured out one night while on blah blah blah........ huh?

    Big amps
    Kenner Close N Play

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