Boss 0D-2 Mods. Turbo Frankenstein mods...

[aab0mb]

Hi,
    I've just finished a round of interesting mods for the OD2. They're for the turbo section and sound really good to me.  If I am mistaken about any info or calculations in this post feel free to correct me.   

Here it is...

http://www.freeinfosociety.com/electronics/schemview.php?id=162

1) Cut the trace that leads  from the r17, Q6 junction to  R11.  Make the cut right before the trace gets to r17 and Q6 were it's already pretty thin.  This location will be the destination for the jumper in step #2.
2) Run a lead from the Q1, r8 junction to the Q6, r17 junction.  The step sends full power (8.2V) to Q6 instead of the starved 5.6V.
3) Remove D6
4) Adjust the RT1 trim (with you DMM) pot so that it splits the power evenly instead of the factory offset.

At this point we have made the turbo section receive full power just like the regular OD section so you'll no longer have the starved clipping op-amp sound.  What's different is that the turbo  section has 2 cascaded discrete op-amps instead of 1 like the regular section.  So, now you can play with the gain response of the first and second discrete op amps to get a gain structure that you like.  Both are set up with a gain of about 50 or so.  Multiply those stages and you have a total gain of over 2500!  I wanted to maintain some of the flavor of the regular section though...

5)  Tack two (or three, or four, or...) diodes across C28 (might have to use leads or remove c28 and make a little diode/cap module) to put them in the         
feedback loop just like the regular section of the OD. 
6)  I lowered r35 to 100k to bring the gain in stage 2 down to around 20 and left stage 1 the same for a total gain of around 1000 when maxed.
7)  Reversed r39 and r32.  As it is normally, it's about a 2 out of 10 volume.  Reversed it's about an 8 out of 10.  Much louder!                 
  Changed C33 and C35 to .1uf for more bass in the turbo stage.

I'm sure there are many thing one could do to the gain/voicing/clipping options of this mod to get a nice result.  Maybe someone would rather have lower gain in the first stage and higher in the second, clipping diodes in the second stage, clipping diodes to ground between stages, etc.  As it is right now I can't even believe it's that same turbo stage that I once hated.  It's smooth, powerful, and much much louder than the regular OD.  It can do clean boost well and with the gain cranked it's a pretty wild ride! 
     If you could manage to "borrow" (via a switch) the other half of the dual gang pot that is not in use when the turbo is engaged, you could adjust both gain stages in the turbo section simultaneously ala the BD2 and Mark Hammer's "The Crank".  Both of the pedals mentioned use the dual gang pot in a different way so I guess it's up to the person to decide whats best for them.  The one last thing I thought of is to rehouse it and have a foot switch for the turbo mode.  Maybe someday...
     My question is, can the diode compression trick be used here? 


Have fun,
Aaron

[blustrat]

Thank you! That is just what i'm looking for. i'll report the mod results here. Bye 

[aab0mb]

Thanks Blustrat.  And, you're welcome.  I had searched around for some possible tweaks to this pedal without much luck besides what Wampcat (Thanks!) put up.   If you need assistance with any of the procedures let me know.  I hope to have a soundclip for these results posted sometime.  If you're successful with you're mods I'd most definitely  like to hear what you come up with.
   

[Sir Applesauce]

Hey, sorry for the late post.
I just modded my OD-2 tonight.
I'm having problems. I think there was a problem where I cut the track, because I tested it after each step
and now there's no on/off. It's just a dim LED and a bright one, but no sound difference.
Any advice?