DOD YJM308 Yngwie Malmsteen Overdrive?

[Arn C.]

My friend has one of these pedals and found it to be too trebly.   I did some mods to the pedal, changed the ic to 741 changed input cap from .001 to .01.
He says it helped but wondered if I could put a hi cut before the volume.   Anyone know what I could do to make this happen.

Thanks a bunch!
Arn C.

[MartyMart]

You could try a simple extra cap across the diodes - to ground say 2n2 or 3n3
Or even at the output jack - signal to ground :-)

MM

[Arn C.]

Thanks Marty, I will give it a try.  I think I will use a rotary switch with a few different values and hang it outside of box and he can find what he likes.

Peace!
Arn C.

[MartyMart]

Yes a rotary switch would be a good option, maybe fit one if there's room - though if it's
a real one he may not want to change the "look" !
I'm pretty sure that 2n2 will suffice.
M

[Arn C.]

Okay, my friend tried it out,  I put a rotary hanging out of the box with capacitors : .001, .oo22, .0027, .oo33, .0039,  .0047
My friend tried them all and said he didn't notice any difference in the highs being tamed down. 

Is there another way to do this maybe across the input cap?
Or is there a way I can put in a tone pot before the volume pot?


Thanks!
Arn C.

[Steve Mavronis]

I have a YJM308 and agree the treble is to too high for my liking. I ended up cloning a 'gray spec' 250 but for your friend maybe try this?

Here are mod instructions from another forum that I made a PCB layout illustration for as a  guide. Personally I'd ignore step 2 and keep that cap to stay in gray specs by just doing steps 1, 3, and 4 below:

[petemoore]

  treble cut...inside the bypass so no LP effect when bypassed.
  Right across the diodes, prime place to start with the mods.
  After fiddling with that circuit much, I figured out I was getting mighty close if not exactly to DIST+ / OD 250 circuit. For those I use a ".1uf? cap/100k V-Rpot across diodes" treble knob.
  Preferring to let the 741 process the HF's, then adjust them at the diodes.
  The LF filters on the YM308 start very 'high' in relation to other stompboxes except perhaps Rangemaster.

[Arn C.]

Thanks Steve!

Pete,    Is this what you mean

http://smg.photobucket.com/albums/v482/arnc/?action=view&current=example.jpg

Thanks!
Arn C.

[WGTP]

An assortment of mods:   

http://www.aronnelson.com/gallery/main.php/v/WGTP/MXR_YJM_DOD250Mods.jpg.html?g2_imageViewsIndex=1

[kurtlives]

Thanks Steve!

Pete,    Is this what you mean

http://smg.photobucket.com/albums/v482/arnc/?action=view&current=example.jpg

Thanks!
Arn C.

Put the cap before the pot. So the pot is going to ground.

The way you have it now you'll have some funky/unwanted relationship with the two controls.

[Arn C.]

Thanks Gents for your assistance!!!!


Arn C.

[Arn C.]

Update:  I used a rotary switch with caps and found out the good match on the cap.  The only problem is that the with a 100K linear pot, only the last bit of the pot is useful,  would a reverse pot or audio pot work better in this case or a different value.  100K L  is what I have in there now.  It is bunching up near the end of clockwise rotation.


Thanks!
Arn C.

[ayayay!]

Update:  I used a rotary switch with caps and found out the good match on the cap.  The only problem is that the with a 100K linear pot, only the last bit of the pot is useful,  would a reverse pot or audio pot work better in this case or a different value.  100K L  is what I have in there now.  It is bunching up near the end of clockwise rotation.


Thanks!
Arn C.

Yes that's typical.  IMHO, trying to kype a tone control for this is worthless unless it's active.  Check the schem for the MXR Distortion III.

My advice is to use a switch for the cap parallel with the diodes and call it a day.  .01 is stock.  If that's too bright, try a .02. 

[Renegadrian]

I built another one and noticed a strange thing I want to report, I am using this ol' topic to keep the forum clean (and keep info togheter)

I made a version with two switches, one is the regular millenium bypass switch, the other is a footswitch (another DPDT)
with 4148s on the two top lugs and red LEDs on the bottom two. center lugs are one on the board output and one to ground.
It works great, I've done the mod before on circuits like this and I love to add switchable diodes.
Its changes are dramatic on clean sounds. 4148s add a good amount of distortion and compression, LEDs give less distortion but more "air" and volume. As the pedal is an overdrive, it can be used with good results on clean amps or to push a crunch channel. I tried the second option and the differences between the two diode positions disappear. veeeeeery strange! Else I tried to push the signal before the pedal, just switching on the stratoblaster inside my guitar, and while there is more boost obviously, the differences stay. Now what?! Did someone else noticed such a strange behaviour on this pedal or similar circuit with a switch on the diodes?! (may it be a TS, etc)