re-issue plexi bright cap question

Discussion in 'Amps and Cabs' started by jezzzz2003, Jan 8, 2008.

  1. jezzzz2003

    jezzzz2003 Member

    Messages:
    2,794
    Joined:
    Dec 6, 2005
    Location:
    aussie
    I believe the bright cap is at C5 on the PCB?

    My question is this, is the bright cap bypassed when the high treble channel is at 10 on the volume? if so Ill clip it off cause I like that EQ,

    does this mean you effectively have all 4 inputs that will sound the same apart from being a plus 6db on both top ins? because that would be pointless.

    Also, do people who have clipped that cap still usually bridge the channels?

    thanks!
     
  2. Gordon

    Gordon Silver Supporting Member

    Messages:
    843
    Joined:
    Aug 19, 2005
    Location:
    Snowflake, AZ
    Is your question about the 1959SLP If so, they use two caps in parallel to come up with a value of approx 5700 pf. I just checked schematic. The bright caps are c17 and c18. Yes, they are out of the circuit when vol is on 10, but that doesn't mean that that will be your tone when you turn down. It will get muddier. My suggestion is to clip them and go to a more usable value like 180-470pf, which you can solder directly on the bright channel vol pot. C5 is one of the caps which bridges the treble channels' blend resistor, do not cut that one, it's part of what makes that channel bright compared to the normal channel.

    Bridging is up to you. I like to get the bright cap to a value that I like, based on the volume that I usually play and just go straight into the bright channel. Yes, the effect is different at different volume settings, low values work well at lower volume settings while higher values are useful when you play at the high end of the volume knob.

    Just confirm that its the 1959SLP that you're talking about so I can be sure that the references that I gave you are correct.

    BTW, go check the Amp Tech Info forum, I'm sure this question has come up before.
     
  3. jezzzz2003

    jezzzz2003 Member

    Messages:
    2,794
    Joined:
    Dec 6, 2005
    Location:
    aussie
    Sorry, I didnt specify, it's a 1987x
     
  4. rockbutt

    rockbutt Member

    Messages:
    249
    Joined:
    Mar 4, 2006
    Location:
    San Jose, Costa Rica
    Yes. The 4700pf bright cap is at c-5 on the PCB of the 1987xRI.

    I suggest you replace it for a 100pf cap. Without a bright cap the amp sounds dark, without highs.
     
  5. Gordon

    Gordon Silver Supporting Member

    Messages:
    843
    Joined:
    Aug 19, 2005
    Location:
    Snowflake, AZ
    Agreed.
     
  6. jezzzz2003

    jezzzz2003 Member

    Messages:
    2,794
    Joined:
    Dec 6, 2005
    Location:
    aussie
    The thing is, Ive been really happy with the amp as it is and dont really feel the need to perform this simple mod, the bright cap seems to give the amp that extra bite, or, gain, when I dial it out a little, the amp is alot less lively and agressive as a solo machine, notes dont sustain as well either.
     

Share This Page