From:
         
         Jeff
    Date:
            11/12/2000 12:47 PM
 Subject:
         Resonance control JCM 800



Hi Guy's,I'm thinking about getting a JCM 800 model 2203. I'm told to look for
one with the vertical inputs. My question is: Is it possible to install a resonance
control feature like the PV 5150 has?Thanks,Jeff 

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   From:
        
        Nigelbrew   (nigelbrew@webtv.net)
   Date:
            11/12/2000 1:35 PM
 Subject:
        Re: Resonance control JCM 800



Yes. I have done this to a few Marshalls. You will need an additional hole, or
you could sacrifice a speaker jack. It is bassically a large value pot,
(100k-1meg) with a small capacitor (like .0047)connected from one leg of the
pot to the wiper. I break the connection of the negatve feed back loop between
the impedance selector an the presence control. The wiper of the pot is
connected to the feedback tap on the impedance selector, which would either
be the four or eight ohm tap and will have a purple wire connected to the
presence control. the pot should be wired like your bass control, so that the
resistance increases as it is turned clockwise. If you mount the pot on the rear
of the chassis, looking at the front of the amp, the cap would be mounted from
the middle lug (wiper) to the lug to the left. The wire which was previously
connected to the feed back tap will be connected to that lug. the third lug is not
connected to anything.