Jump to content

LINE 6 MM4/DL4 Volume Fix (without using SMT resistors)


Recommended Posts

  • Members

LINE 6 MM4/DL4 Volume Fix (without using SMT resistors)

This is something I performed and documented on my MM4. I posted on TGP, but since it is down---I figured I would pass the knowledge on here.

1) Replace all the input/output buffer components with high quality parts for clarity of signal. Remove the electrolytic caps (C4 and C8), replace with
Nichicon and WIMA; Remove TL072 op-amps (U3 and U22) and replace with Burr Brown hi-fi OPA2134UA.

2) Removing RF filter caps from pre-relay inputs and post-relay outputs (C1,
C36, C23, C24) in order to make the pedal TRULY true bypass and eliminate tone sucking.

3) Reduce R36 and R37 from 36k to roughly 22k (24k according to Jeorge Tripps) for increased gain of output buffers. This will fix the "volume-drop" problem some people experience.

#2 and #3 are crucial to do. #1 is just for tone snobs. Furthermore, #2 was caught pretty early in the revision history so pedals built after 2001 already have this implemented.

STEP 1: Take your pedal apart!

Line6MM4fix001.jpg
Here is my road beaten MM4. Actually, I bought it used (aka pre-beaten) off of EB*Y.


After taking the screws off the back, your pedal should look like this. Slide the battery clips out. Then remove the 4 black screws. Then remove the silver retaining screw/nut in center. Remove nuts from input/output jacks.

Line6MM4fix004.jpg

This is what you should have left. This is the part you have to work on. Now turn it over!

STEP 2: SMT FUN or "How the hell do I remove these small components?"

This is when things start to get interesting. R36/37 are indicated in the picture. Pretty freakin small, huh? A steady hand with your soldering iron is mandatory! If you have had 4 or more cups of coffee, I do not recommend attempting this. Go for a walk. Read through a Mouser catalog. Come back in 4 hours...

Line6MM4fix006.jpg
Desolder the resistors by heating up one end and quickly shoveling it off the PC board WITHOUT damaging the copper pads.

STEP 3: Installing 22k resistors or "So this is how a square peg fits in a round hole."

At this point, you notice there are no nice holes to run your resistor leads through. Some of you might get discouraged at this point, but you can make it work! Take your resistor, make a small 'L' at the end of the lead, and solder the 'L' to the pad.

Make another L fold over the resistor. I used some heat shrink to prevent contact with the next resistor that you have to wrangle on. Repeat this step for R37.

Line6MM4fix010.jpg
When it is finished, your eyes should be as blurry as this picture. You should get the idea...


STEP 4: Put it back together and test it! (...some prayer might help at this time. Consult whatever electronic God you choose to dialog with.)

Line6MM4fix011.jpg

I tested mine, and NO MORE VOLUME DROP! Hopefully this helps everyone.

Link to post
Share on other sites
  • 1 month later...
  • Replies 58
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

  • Members

C4 and C8 are the two electros right near the second to last jack on the right in your pic - what should be the Right Input jack.

C4 is on the bottom and C8 is above it almost touching the bottom left of the Right Input jack..?

Link to post
Share on other sites
  • 2 months later...
  • 1 month later...
  • Members
Quote Originally Posted by emokiller89 View Post
I like to do step 3 but i dont know how much watts the resistors need to have?
What resistors can i use? Metall or the other ones?
please help
You'd probably want to use 1% metal film 1/4W parts. Be sure before you go soldering to SMT pads that you're comfortable with your iron & technique. Of all the mods in the DIY kit I sell, this is the only one folks have had trouble with. If you can, find a used/dead PC motherboard or something similar to practice with - EASY once you've got 'the touch', but deadly (to the PCB) if you don't. thumb.gif
Link to post
Share on other sites
  • Members

Another shot of the original SMT resistors:

14.jpg

And the 1/4W parts (before cleaning PCB, whoops):

14a.jpg

Then, I like to slip another piece of heat shrink over the top & bend them gently over. . .

14b.jpg

For those looking to get super-fancy, you can get a warm air reworking station on Amazon for

Link to post
Share on other sites
  • 4 weeks later...
  • 2 weeks later...
  • Members

Sorry nobody had replied to your post! I was linking someone to this thread as a reference & just saw.

You don't replace them, just remove them. Most pedals won't have them in the first place, just check to see if they're present on your board. If they are, you're in for a nice treat as the bypass is improved w/o them. wink.gif

Link to post
Share on other sites
  • 2 months later...
  • Members
Quote Originally Posted by Gantz View Post
Does anybody know what the value of R31 is?...My soldering tip took it off by accident!
Sorry I hadn't gotten back to you yet - sometimes slow to respond to PMs. wave.gif

R31 (next to switch 'C') should be 4k. Its a 1% part marked 4021 (4.02k).

FYI - if you want more info on replacing surface mount parts, you can read THIS.
Link to post
Share on other sites
  • 1 year later...
  • Members
cry.gifcry.gif hi everybody...i wanted to do the mod for the volume drop...so i changed the r36 with a 22k and everything went right, then i did the same with the r37 but unforunally i made a s...t and now i have a dl4 WHITOUT the r37 resistor....BUT IT WORKS! can i know what the r37 is for???? why my dl4 still works!?!?!?! confused.gifconfused.gifconfused.gifconfused.gifconfused.gifcry.gifcry.gif:cry.gif
Link to post
Share on other sites
  • Members
Quote Originally Posted by drasp View Post
Re-read the instructions. wink.gif
hi again, this is what Keeley replyed to me:

my question
"hello, i have a problem and i hope you can help me.
i have done the mod on a line 6 dl4, for the volume drop, and i have changed the R36 resistor with a 22k, but i have broken the R37 place and i can't anymore solder the new 22k here too! but my dl4 works anyway!!! can i know why?!?!? what the R37 is for??? thanks!
best regards Simone"

answere
"Howdy sir!
R37 is a 36K resistor, it may work without it, it is probably designed to set a bias voltage or maybe a pull-up resistor, haven
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...