Boss OS-2 Mods

[ghostsauce]

So, I have this boss os-2 and I have the parts list for a few mods that can be done to it, and I plan on experimenting with different values & such but for now I just want to try putting different input caps on a toggle switch so I can boost the bass.  Cause it has none.  I don't know how to do it or what kind of switch I could/should use. I want to take C27 and be able to toggle that value between the stock value or a few different ones. Or even just one other if it's a big hassle.

Also, I wanted to make the info I have about this pedal available to you guys since it took me forever to track it down.  Here's the schematic and mod info:
http://ghostsauce.net/random/Boss%20OS-2%20-%20Schematic.jpg

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

[nocentelli]

For the cap switch, I'd use a DPDT toggle switch. Let's say you want three different values, 0.047uf (stock), around 0.1uF (more bass), and 0.22uF-ish (lots of bass). You could get a 3 position on-off-on DPDT and solder caps across the lugs to give the three values - Here's an example from a pedal I did:



Remember capacitance wired in parallel is summed, so on the above example, the centre position ("off") gives the stock 47pF, "up" adds the 100pF to give 147pF, and "down" gives 5047pF.

For your values, you could have the stock 0.047uF in the middle, another 0.047uF at the top to give 0.094uF, and maybe a 0.22uF to give 0.267uF for the bassier setting. You just need to remove the stock cap from the board and run a wire from each terminal to the "in" and "out" lugs. I think a bigger problem will be how you will accomodate the switch in the Boss enclosure - They're a pretty tight fit...

[ghostsauce]

Wow, finally somebody puts it in layman's terms. Thank you! That's actually pretty easy. Man I now have so many options available to me for modding other pedals... Thanks!!

[nocentelli]

No problem. 

For future mods, if you only need two alternate components you can just use a SPDT instead of a DPDT: Remove the original component from the board, and run a wire from one connection point on the board to the central pole lug. Solder the two different components to the outer two lugs and run wires from the ends of each and connect both to the other original connection point on the board. Now the signal is sent from the board to the switch pole, and back to the board via either of the two alternate components. Just remember to observe correct polarity for polarised electrolytic capacitors.

[WGTP]

I haven't had a chance to compare yet, but here are some I did a while back.   

http://www.aronnelson.com/gallery/main.php/v/WGTP/Boss_OS_2_Mods.gif.html?g2_imageViewsIndex=1

[camogli]

Remember stock for C27 is 47nF (0.047uF) not 47pF as in the pic, I made a mistake confusing.
Thanks for the helpful mod

[fbeghini]

What kind of capacitor is C27? I can't find a 8nF capacitor.

[fretzburner]

Tried to add diodes in the distortion section making it 2x2 increase the distortion volume and seems to overdrive the transistor Q2 following it..How to level it to the OD section?

photo hosting sites
I'm thinking increasing R23 or decreasing R32 and not sure if it will not affect the tone.
Need some tips. thanks

[Renegadrian]

got an os-2 in a trade, as soon as I got it I starded modifying.
I got the schematic, one thing that came to my eye is that schem calls for a 47n in C27, while stock pedal has a 4.7n (472) cap in that position.

[Steben]

The whole concept of this pedal is brilliant. The scooped distortion tone is a bit of a bummer though.
Although I must admit the color control is more of a "play thing" for a short time with everyone having their sweet spot.
Perhaps it is better to change the pot with a trim pot on the side and use the pot for an extended tone control (like mids), but you kinda kill the original pristine circuit of course.

Worth mentioning is that the drive channel is a sd-1 type with a low roll off corner frequency of +/- 330 Hz instead of 720 Hz.