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    Mark III question

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    harpy

    Posts : 94
    Join date : 2012-02-04

    Mark III question

    Post by harpy on Sat Jun 22, 2013 12:07 pm

    If you look at the build instructions for a MkIII one of the mounting lugs on the quad cap has a wire ground to V1 ground lug.  The 11.2 bias resistor mounts from V1 to the same lug on the quad cap.  Is it for redundancy?  I was also wondering if there was any down side to a SDS quad cap board verse a Dynakit quad cap.  I was thinking they would be pretty much the same circuit, but I am not very savvy understanding circuits.

    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Mark III question

    Post by sKiZo on Sat Jun 22, 2013 1:49 pm

    Don't quote me ...

    ... but I'd expect it's a timing thing. The additional point to point connection should theoretically eliminate any delay or hash generated in the board by other components attached to common ground.

    PS ... I get a dancing banana if I got it right. Razz

    harpy

    Posts : 94
    Join date : 2012-02-04

    Re: Mark III question

    Post by harpy on Sat Jun 22, 2013 9:37 pm

    I noticed on one manual it's not wired at all and another includes it.  It must have been added at some point.  The newer manual that has the diode in place adds the ground wire, the one with the selenium rectifier doesn't.  I am running Dynakit's dual bias kit and may add the ground on both the bias resistors.  Do it the original way on the quad cap one and on the added bias resistor run that to the V2 ground lug.
        It's hard for me to stop tinkering with them.  I would like to try a VTA board, but then there are Bob's Monoblocks that look really nice and would be a better fit for my speakers.  I also like the fact it can run on 1 bank of driver tubes.  Run lean in the summer and jam in the winter.

    hawaii.ken

    Posts : 157
    Join date : 2012-01-31

    Re: Mark III question

    Post by hawaii.ken on Sat Jun 22, 2013 9:45 pm

    The "wire ground to V1 ground lug" was to ensure that the bias cap connected to the other V1 ground lug had a path to ground.

    harpy

    Posts : 94
    Join date : 2012-02-04

    Re: Mark III question

    Post by harpy on Sat Jun 22, 2013 9:52 pm

    Oh, Ok it has nothing to do with the bias resistors.  Should I add it?  I was using the older manual and neither amp has it.

    hawaii.ken

    Posts : 157
    Join date : 2012-01-31

    Re: Mark III question

    Post by hawaii.ken on Sat Jun 22, 2013 11:20 pm

    harpy wrote:Should I add it?
    It would depend on how your amps are currently wired. If you have anything (besides the wire) connected the any of the V1 grounding tabs you should leave it in or add it in. Most current mods don't use it.

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