Awesome Boss OS-2 mod - build report

[ghostsauce]

Details on the mod are below. What was once a noisy, could've been awesome but didn't come close paperweight in a drawer in my workbench has now been turned into a monster tone generator!  This is the pedal that has the overdrive and distortion circuits that can be blended together.. anyway, it sounds rich and full now, and I can also dial some really gnarly tones out of it for that in-your-face sound. The added mid pot was a nice touch, although it doesn't quite sound like you'd expect because it only controls the mids on the distortion side..

Also D8 and D4 becoming LED's in the signal path looks really nice as you play, especially if they are different colors, since they are both in a different circuit they light up differently even when the blend knob is at noon. Gives a really neat effect, and I'll be drilling a few extra holes in this thing so I can mount them on the outside.

Between this, my Dr Boogey, and a fuzz I can pretty much get anything now. Just thought I'd share, this mod isn't new but it really changes the thing for the better.

Big/Full/Fat Mod:
Overdrive Circuit:
D8 - LED    
R2 - 6.6K
R39 - 1K
C27 - 0.008 uF
R37 - 10K

Distortion Circuit:
R30 - 1K
C18 - 0.1 uF
D3 - 1N4148 + 1N4148 in series
D4 - LED
R23 - 10k
C19 - 0.47 uF
C16 - 0.0047 uF
C20 - 0.047 uF
R32 - 47K

"Marshall" Type tones:
C28 - 0.22 uF and 1K connected in parallel
D8 - LED
D3 - LED
C27 - 0.047 uF
C23 - 10 uF
C18 - 0.47 uF

Fun changes:
Clipping Diodes: LED's, germanium, or 1n4001s - LED's will make it a bit fuller, louder, and more bass. Germaniums will give it more of a tube flavor, 1n4001s will increase the distortion/overdrive capability
C27 - 0.22 uF / 0.15 uF / 0.1 uF / FOR BASS GUITAR, MAKE 1 uF - Adds bass on od side
C16 - (Experiment with 0.022 uF, 0.033 uF, 0.047 uF, 0.068 uF, 0.1 uF or higher) - Increase value for more mids on dist side
R27 - 1-22K, or you could install a pot in its place to control mids - Lower value for mid increase on dist side

[Brunz]

Hi, I'm a new member, and I joined because I've been modding a Boss OS-2 with a Monte Allums dual stack kit. It still sounded thin and the kit included a RC4558p, and 2  NE 5532 op's. I found, by mistake it got louder and cleaner with out the D4, I put a pair of wires to use as testing the Diode choices., the n4001 sounded ok but when it fell off the sound improved more than the kit did. C16 was the first improvement a .15 uf opened up the muffed bass.
     I wouldn't recommend anyone to buy a OS-2 due to the 1/16" traces and super thin layer. The solder sucker lifts up the circle trace if the tip of the iron isn't holding down. What a P.O.S. I had to repair almost every swap. Now, I found other Boss boxes, NS-2 kit M.Allums worked well.
     I had years earlier modded a Blues Driver-2 using Keen notes found on the Net, so I went back in and pulled the op-amp and used a NE5532 stack I bought in addition to a Tremolo kit.
     BD-2 mod is amazing for BB king pulls, so I have just modded a SD1 with success using Net mod tips. The dual piggy back jrc4558dd / a 4558p. worked but did not improve anything except noise. It fits with a chip socket pressed on. Bigger caps and diode add on's worked fine.
    So does anyone else have a fully explained mod list for the OS-2. This is fun but frustrating when the quality of the board is crap. My wife worked for Fisher metal detectors in Los Banos and hand built them, tuned the pick-up coils. Those are good boards and heat resistant components. I have some spares and plenty of silver mica parts in Sunnyvale Ca. I want to learn this mod trade for spare cash, since I'm retired.  thanks for reading, Ken

[Kennt82]

IIRC, this is  a simplified Rat and Tube Screamer in parallel, that you can mix into a shared tone section.  Try some of the individual Rat and TS mods?