Features for JLM PM2000 EQ MOD KIT

  1. Picture of new JLM EQ mod kit. This mod kit when applied to High Mids or Low Mids of a PM2000 type desk will change the narrow Gyrator (IC) type EQ into fully inductive (LCR) wider EQ. One mod kit is needed for each high or low mid band.

Before you start

  • Check that the PM2000 Channel  is working OK.


Firstly, build up the eq mod PCBs according to the photo's below and or PCB overlay with the table of values at the bottom of this page.  L1, C1 and R1 are for the lowest freqs and will have the largest value capacitor and inductors. 

Note that the inductors on the low mid PCB below are all in series to ground and so are mounted on the PCB with their pins aligned horizontally down the PCB (see photo below).   



The first three inductors on the high mid PCB below are in parallel to ground and so are mounted with their pins vertically on the PCB.  The last (smallest) inductor (L5) is mounted vertically and the L4 position is linked over vertically (with a component leg or solid wire).  This is because the top two freqs use the same value inductor so instead of having a redundant inductor there we can put L4 and L5 in series and save an inductor.





 1  There is a row of five stand up resistors on each of the two eq switch PCBs that the eq mod PCBs wire to.  See the photo to identify these resistors.  Heat each pad that they are soldered to and pull them out.  Again be careful not to heat the pad for too long as you don't want to damage it or oxidise the solder on it much.  Once all of the resistors are out, add just a little fresh solder to the row of five pads closest to the front of the module.  These are the pads that the eq mod PCB will wire to.  When you're done there should be a small round shiny blob of solder on each pad, with no shorts in between the pads, ready for you to solder the ribbon cable to.

 2  Hold the two eq mod PCBs together as shown in the photo and use the two cable ties in the kit to hold them against each other and to one of the wiring looms in the top of the module.  Each module is different so you may or may not need more cable ties to hold the boards in position.  You need to mount them so they stay roughly in the middle of the module and don't catch on adjacent modules when you put it back into the console.  Be sure to mount them so that the low mid eq ribbon cable will reach the low mid switch PCB.


3  Trim the ribbon cable from the high mid eq mod PCB so that it reaches the row of pads you've just prepared on the high mid eq switch PCB, with just a little slack.  Now separate the individual wires in the ribbon cable and peel them back so that they separate roughly where they pass the pot on the eq switch PCB.  Then cut the Red, Yellow, Blue and Grey wires at this point.  They are all ground and are there to shield the wires carrying signal to the eq mod PCB.  The Brown, Orange, Green, Purple and White wires wire to the eq switch PCB and the black wire gets peeled back further and soldered to a ground tag on the main PCB.  Don't do this yet though.


4  Strip about 2mm of insulation from the ends of the Brown, Orange etc wires and tin them.  The tinned wire must be short so that none of it hangs past the pads on the switch PCB.  Starting with the white wire at the bottom, solder it to the pad by holding it to against the middle of the pad and pressing your iron quickly against it.  Don't heat the joint more than is absolutely necessary as you don't want to ruin the solder and have to remove it.  Remember these are the five pads closest to the front panel of the module.  Repeat this with all the other wires and when you're finished, inspect the joints and make sure they look good (shiny and round) and no solder has run between any of the pads, shorting them together.  Then repeat this whole procedure for the low mid eq PCB.

5  Pull the black wires from both ribbon cables back so they can reach the ground tag on the edge of the main PCB, labelled O1, that has a black wire going to it.  Strip and twist the two black wires together then tin them.  Add a little solder to the ground tag and solder the two black wires onto it. 

6  Finally, inspect your work and check where the eq mod PCBs are sitting.  If they look like they're hanging past the edge of the module you may need to adjust them.  This will be different in every module you do.


Your channel is now modded with inductive eq for the mid bands!  You can test them by playing music (anything wide band) through the channel and turning each band in turn to full boost, and switching through the freqs.  They should sound like they line up to the freqs in the table at bottom of this page and there should be definite changes when you switch between them.  Also the amount of boost (or cut) shouldn't change drastically when you change freqs.  You might now be noticing how much you can boost normally ugly (and even nice) freqs without the eq sounding bad.  Hopefully this will bring as much joy as it brings me

Again, congratulations on your DIY skills and your willingness to have a go.  Welcome to the club!



PART #             FREQ               Q                      L                      C                      R


1                      115hz               0.9                    600mH              3.3uF                0ohm

2                      160hz               1                      480mH              2.2uF                91ohm

3                      220hz               1                      360mH              1.5uF                180ohm

4                      330hz               1                      240mH              1uF                   270ohm

5                      615hz               1                      120mH              560nF               390ohm


1                      1.5k                  0.79                  39mH                270nF               470ohm

2                      3k                     0.71                  18mH                150nF               470ohm

3                      5k                     0.8                    12mH                82nF                 470ohm

4                      7.35k                0.8                    5.6mH               56nF                 470ohm

5                      10k                   0.72                  5.6mH               47nF                 470ohm