Boss OS-2 Mods

[WGTP]

The Boss OS-2 overdrive/distortion is conceptually a cool pedal.  It incorporates an SD-1 overdive and DS-1 distortion type circuit into a single pedal with a blend or "Color" control to allow panning between the 2.  The overdrive is midrangey and the distortion has a notch filter, which  accentuates the difference between the 2 and allows for the mids to be adjusted with the Color control, in addition to blending the 2 different types of distortion.

The drawback, as can be seen by the treads modifying the standard Boss pedals, is that both can be modded to sound better than stock.  Most mods for those 2 pedals will work for the OS-2, being careful not to vary the level of either circuit and screw up the balance/pan/"Color" control.

Since identifying the correct part numbers to mod could be difficult, I have incorporated mods that I think should sound good into the schematic of the OS-2.  The mods are in Blue.  Let me know what you think.   

http://aronnelson.com/gallery/WGTP/Boss_OS_2_Mods?full=1

[WGTP]

I have difficulty with subtleties.  Part of the cool part of this pedal is blending the 2 types of distortion.  Not only is that the difference between diodes in the loop and diodes to ground, it is also the asymmetry/EQ of the OD circuit and the symmetry/EQ of the Distortion circuit.  I'm also assuming the clipping level varies at different rates for both pedals as well, giving multiple clipping thresholds mixed at the selected level.  The OD circuit doesn't seem to be as "Hot" as the Distortion side. 

That said, the mod I proposed for the distortion should include 2 diodes to keep it symmetrical, rather than the single I added in the schematic.  I'll change the schematic when I have a chance. 

The mods may have the effect of making the 2 circuits sound more similar, which might work when using one or the other, but sort of defeats the idea of blending the 2.   

[Khas Evets]

If you add two diodes to the distortion side, you will double the output of that side, which could throw off the balance of the two circuits. Just something to consider. It will make the clipping less compressed, which a personal taste thing. I happen to prefer it. You could also try a pair of LED's.

Making the overdrive more asymmetrical may be interesting. I'd have to hear before I could comment. That will increase the output, which may help counter the increased threshold on the distortion side. Another option is to add a diode on the D7 side. That would keep it asymmetrical and increase the output. This may keep the balance between the two channels in check.

By the way, what opamps are used in this circuit?

[WGTP]

I was suprised to see a JRC?1458 in the clipping stages and an inline something or other for the other op amps.

I'm thinking rolling off the highs on the distortion and raising them on the OD should help maintain the balance, along with both diode changes, plus make changing the the tone control less necessary when going back and forth between the 2.

The more I mess with this, the more I think the mods may be less necessary than for the stock SD-1 and DS-1 because of the versatility provided by blending the 2 different distortion circuits.   

[Caipira]

Hi, could you please make a list of what should be replaced ? Something like:
R6 - 4.7k to 2.2k etc.
I don´t know know how to read those schematics , I´m just a musician that barelly knows how to
solder and unsolder some parts.
Anyway, thank you very much for your time and mods.

[wampcat1]

.....

[WGTP]

Cool.  I forgot about this thread.   

[WGTP]

Interesting mods.  I was more focused on smoothing it out and boosting some highs and the mods are mostly to increase the bass.   

I was looking at the dual RC network off of the feedback loop of the distortion and it is essentially the same as a Rat with slightly different values that produce an even more pronounced mid dip and bass boost.  See this Rat Mod thread for more info. 

http://www.diystompboxes.com/smfforum/index.php?topic=45122.msg331481#msg331481

I also think the notch filter on the distortion is ripe for some mods. 

R29 at 4.1k looks like it could be raised or lowered to increase/decrease the drive of the distortion circuit, possibly to rebalance things if other mods mess up the balance.

C23 4.7uf can be increased to 10uf for more bass and drive in the OD section.

Now for a series/parallel switch... wait, that is probably a different pedal.   

[WGTP]

Now that I think about it, R29 can't be a 4k1.  That would mean max resistance in parallel with the 270K pot would be about 4k.  It needs to be more like 100k.  I'm thinking it must be 470k or something like that to result in a value around 150k which sounds about right.   

[wampcat1]

Now that I think about it, R29 can't be a 4k1.  That would mean max resistance in parallel with the 270K pot would be about 4k.  It needs to be more like 100k.  I'm thinking it must be 470k or something like that to result in a value around 150k which sounds about right.   

It's a 4.1meg, not 4.1k

here's a schem:
http://www.freeinfosociety.com/electronics/schemview.php?id=163

bw

[WGTP]

Looks like that has some values fixed.  4.1M should get it cooking good, and it still is a good place to fix the drive balance if other mods mess it up.   

[jamesmarkjackson1979]

Has anybody thought or tried modifying the circuit to oscillate between the two circuits at different speeds. I'm trying to work out how to do this. I'm guessing I'd need something like an LFO or tremolo/panning circuit in place of the Colour knob. Any ideas?

[ElectricDruid]

I did something like this with the Big Muff tone control, which is a similar pan/crossfade between (in that case) a highpass and a lowpass filter:

https://electricdruid.net/single-vca-crossfader/

You could replace the two filter circuits with the two distortion circuits and give it a try.

HTH,
Tom

[Steben]

Sorry to bump this thread. Yet I read something very interesting here. I do think the stock sounds good as long as you blend the two enough.

[ThePracticalPeasant]

Sorry to bump this thread. Yet I read something very interesting here. I do think the stock sounds good as long as you blend the two enough.

I'll join the bump as I own one of these; it was actually my very first pedal. I'm suddenly interested in the original mod here as I kinda generally hate the thing how it is. I much prefer the overdrive tone from the BD-2; the distortion is okay, kinda lackluster, and the primary reason I figured I'd try to build pedals (I'm wise enough to realize it'll be plural) 

[Steben]

Sorry to bump this thread. Yet I read something very interesting here. I do think the stock sounds good as long as you blend the two enough.

I'll join the bump as I own one of these; it was actually my very first pedal. I'm suddenly interested in the original mod here as I kinda generally hate the thing how it is. I much prefer the overdrive tone from the BD-2; the distortion is okay, kinda lackluster, and the primary reason I figured I'd try to build pedals (I'm wise enough to realize it'll be plural) 

Just a guess: you mainly use humbuckers? glued neck guitars?
On average I notice as a mainly single coil/strat lover I tend to like what mainly humbuckers/LP lovers dislike.

The mid boost effects (SD, TS) etc.... work much better on a strat for example. And the OS-2 adds some scooped mid distortion to it. It does not sound that bad at all on single coils. But the gain needs to be mid(low)ish.
The BD-2 is a black and white pedal. People love it or have a nah feeling. I'm with the second (on strats).

[ThePracticalPeasant]

Just a guess: you mainly use humbuckers? glued neck guitars?
On average I notice as a mainly single coil/strat lover I tend to like what mainly humbuckers/LP lovers dislike.

The mid boost effects (SD, TS) etc.... work much better on a strat for example. And the OS-2 adds some scooped mid distortion to it. It does not sound that bad at all on single coils. But the gain needs to be mid(low)ish.
The BD-2 is a black and white pedal. People love it or have a nah feeling. I'm with the second (on strats).

I tip my cap at your insightfulness. You are correct that I don't own a guitar with a single-coil pickup. My two primaries are an HHH Franken-Squier and a set-neck/arch-top HH Ibanez.

My experience has been that blues driver->compression with a bit of delay/reverb on the output does a fairly job of a generic blues/rock tone, at least with the humbuckers in my guitars and lackluster amplifiers I plug into. The OS-2 makes the odd appearance after the compression, max drive colour to full distortion for a late-90s alternative sound, but to get it to tone right the guitar volume needs to be way up and playing gets really noisy...

The Squier has a Duncan Hot-Stack for Strat in the middle, closest I have to a single-coil. Perhaps I should give the OS-2 a fair shot with that pickup specifically.

Edit: Calling my 90s solid-state Fender "lackluster" probably wasn't fair; it's not junk, the clean channel is quite nice, but it's nothing spectacular, and it's unlikely to be contributing anything special to the overall tone.

[Steben]

Just a guess: you mainly use humbuckers? glued neck guitars?
On average I notice as a mainly single coil/strat lover I tend to like what mainly humbuckers/LP lovers dislike.

The mid boost effects (SD, TS) etc.... work much better on a strat for example. And the OS-2 adds some scooped mid distortion to it. It does not sound that bad at all on single coils. But the gain needs to be mid(low)ish.
The BD-2 is a black and white pedal. People love it or have a nah feeling. I'm with the second (on strats).

I tip my cap at your insightfulness. You are correct that I don't own a guitar with a single-coil pickup. My two primaries are an HHH Franken-Squier and a set-neck/arch-top HH Ibanez.

My experience has been that blues driver->compression with a bit of delay/reverb on the output does a fairly job of a generic blues/rock tone, at least with the humbuckers in my guitars and lackluster amplifiers I plug into. The OS-2 makes the odd appearance after the compression, max drive colour to full distortion for a late-90s alternative sound, but to get it to tone right the guitar volume needs to be way up and playing gets really noisy...

The Squier has a Duncan Hot-Stack for Strat in the middle, closest I have to a single-coil. Perhaps I should give the OS-2 a fair shot with that pickup specifically.

Edit: Calling my 90s solid-state Fender "lackluster" probably wasn't fair; it's not junk, the clean channel is quite nice, but it's nothing spectacular, and it's unlikely to be contributing anything special to the overall tone.

By the way, solid state amps are a delight to mod. In a nutshell: They work on stompbox voltages and are not a fortune to destruct.