Boss - BD-2 Blues Driver 1995  [schematic]

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lespauldoc
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Post by lespauldoc »

Well, as a lurker here for years, I hope I don't get blasted.

Did the Galaxie mod today as I've been screwing with EVERY BD mod and came to the conclusion i HATE the pedal. This mod is truly something different from all the other BD mods out there. I pulled the schematic because I want to fully understand what is happening. That crappy diode to ground crappy-clipping is gone, and smooth. Gain is 1/3 what the stock is (like you'll ever need that much?), and actually sounds bluesy. A bit too tight bass to my ears, but reminds me of a 2x10 cab. I prefer looser bass, so I may screw with fattening that up a touch-- like a 2x12 or so. :roll:

Overall, this turns the BD2 into an amp-simulated drive, like a good preamp. The transistors (all FETs? Gotta look) are sparkling and clean. The pedal is more of a dirty boost that really sings. "Splatty decay" is gone, for real. Every other mod I've tried that "splat" is minimized at best.

Oh, and I put a hot green LED for indicator in there--- can I change the resistor to make it super bright since I switched other resistors? :twisted:

Well done on the mod. I hope people actually hear about this one! :applause:

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Post by DrNomis »

The only mod I've made to my Blues Driver is to replace the original Red indicator Led with a Blue one, other than that mine's all stock standard, for me, I find that the Boss BD2 Blues Driver is a bit like the Ibanez TS9 Tube Screamer, although the circuits are completely different, the Blues Driver doesn't have the midrangey-ness of the Tube Screamer, I tried the British Blues sound settings as illustrated in the Blues Driver manual and found that I really like it, honestly to my ears I can't for the life of me hear the splatty note-decay that some say is evident in the Blues Driver sound, maybe I just happen to have one that doesn't suffer from that issue...I don't know...... :thumbsup
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Post by JRM »

I might do the Galaxie mod to my BD-2. I liked what I've heatd on youtube and I agree that if you really want to change the pedal you've got to change (at least) the values of the components. Just upgrade components might reduce noise issues (GE-7 is a great example) or give some small improvements but don't change the sound. When I read Analogman statement: "This BD-2 mod does not drastically change the circuit, but replaces many cheap, poor sounding components that Boss used. This is similar to what the high-end home audio guys routinely do when they buy a piece of equipment - they spend a few hundred dollars putting in the EXPENSIVE capacitors which lets the true sound come through. We are also changing circuit values in several places to make the tone control more useable and less shrill high end" I started to think that his mod had a lot of snake oil added... I know a bunch of high-end home audio guys and they don't change caps for sure because their equipments already have excellent quality caps. But high-end audio is flooded with snake oil, being easy to find cables that retail over €5.000 and are just two wires and lot of engineering nonsense.

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Post by latestsaint »

hey i know this was a while back, but i wanted to try this mod out...

one question tho. is this a typo? D6 does not look like it is even close to the clipping diodes. Did you mean D7?

Thanks
new_anuzzerone wrote: D6, D8, D9, D10: 3mm red LEDs (I like water clear high brightness) These are clipping diodes. LEDs make the pedal fatter, tighter and more compressed. I also find they add some dynamics to the pedal. They also clip much less than a standard diode so more headroom!

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Post by Keith_A »

JRM wrote:I might do the Galaxie mod to my BD-2. I liked what I've heatd on youtube and I agree that if you really want to change the pedal you've got to change (at least) the values of the components. Just upgrade components might reduce noise issues (GE-7 is a great example) or give some small improvements but don't change the sound.
I think there's definitely merit to using "upgraded" components for means of noise reduction and such, but the purpose of an overdrive is to add clipping. I think a lot of people get too anal about background noise, much of which is masked unless you are playing in your bedroom. Or people are intently listening to the background noise, because we've been sold on the issue that it's a problem. It's a fabricated problem.

There have been tests done on the negligible effect of distortion from capacitors or resistors, and how again, with a device intended to create clipping, that hearing those effects is what I refer to as being like seeing single snowflakes in a blizzard. Maybe you can catch one here or there, but so what?

I honestly don't know what would actually need "upgrading" in the BD-2 with just component swaps that are part-for-part the same values. Boss went with very good jFETs for it. The op amp stage is simply a post-volume mild bass boost. It doesn't have a wacked out Q or it would stick out like a sore thumb. For that reason alone, what is the need to replace the op amp? General purpose for this application is okay.

I can also honestly say that I've used all sorts of general purpose components in the BD-2 and haven't heard any performance differences. I've installed the Galaxie Mod using just the original types of Boss caps, or similar mylar types, and have also used ceramics similar to what Boss used, or have used those little multilayer jobs without issues. I've A/B'ed them with cheap/upgraded/mixed and hear no audible differences.

The BD-2 has a mostly crammed up PCB. I think it makes more sense to use components that will fit without problems. The box caps or metal film types are good simply because they have 5mm spacing that allows them to drop right in. But that said, there are cheaper alternatives that usually have 5mm spacing. The BD-2 also uses 1/8-watt resistors. There's no point in replacing them with 1/4-watt (unless that's all you have), since a chain is only as strong as its weakest link. You'd have to install them like they are done in a Tube Screamer, which means there's the possibility for something to short out or make contact where it shouldn't.

There's also a pair of ribbon cables in the BD-2 that I frequently see that someone has damaged. I think it most commonly happens when they are trying to sub out the op amp, or shotgun out all the electrolytic caps, because most of them are packed in that end of the PCB.

If someone wants to replace parts just for grins, I don't have a problem with that. Some people find it to be a good way to pass the time, I guess. I'd rather just focus on changing things that are going to have what is (hopefully) a positive AUDIBLE impact, and do no more or less.

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Post by Bozo1996 »

I modified my Blues Driver so it could be used as a boost/overdrive/distortion for both bass and guitar. Here's my list of changes.

C8 - 10nF
C9 - 100nF
C10 - 68nF
C14 - replace with jumper wire
C16 - 3.3nF
C17 - 10nF
C19 - 39nF
C22 - 100nF
C26 - 1nF (slightly lowers high frequencies)
C36 - 100nF
C100 - 33nF
C101 - 100nF

R9 - 47k (increases opamp output volume and seems to increase headroom/gives the gain a fuller feel.)
R21 - 1k linear pot (mid contour control)
R26 - switch wired across the resistor in parallel (bright boost)
R27 - 6.8k (lowers minimum gain of 2nd gain stage)
R29 - 4.7k (lowers minimum gain of 1st gain stage)
R34 - 10k with 1k resistor on switch wired in parallel (gain cut/boost)
R37 - 220k
R51 - 20k linear pot (mid control)

D2 - mosfet clipper (gate tied to drain)
D3 - remove
D7 - germanium
D8 - LED
D9,D10 - replace with a single LED

Experiment with the diodes, they don't necessarily need to be exactly what I put in mine, they just need to clip asymmetrically. I probably will use a different diode configuration for each one I modify.

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Post by Vinz35 »

HI everybody,

Could someone show me how to do the Phat mod switch from the keeley mod with a schematic ? Can't find one on the internet.

Thanks

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Post by nooneknows »

aab0mb wrote: 24 Oct 2013, 17:23The od2 has the clipping in the normal section within the feedback loop. More of an overdrive sound that's compressed instead of the clippers to ground in between stages like the bd2. So! Remove diodes to ground and tack them in either feedback loop. I did the first one and used the second stage as makeup gain.

Now let me tell you.... This. Thing. SUNG! There's a LOT of gain to play with so it can get a little over the top but all in all the splat is basically gone. Feedback loop clippers people. Makes it a different pedal, I'll admit, but it retains a LOT of the full range clarity that it's known for. The mod tames the high end a bit and smooths the splat. bottom line. I really hope someone tries this. It's probably one of the most drastic and pleasing mods i've done to ANY pedal and it's relatively easy.

Note: easiest thing to do is use the little 100pf cap in the feedback loop as your tack on point for the diodes. One could make a mini board module to wire in diodes +cap if they chose. Whatever works for neatness as it's kind of a hack to the circuit. Nondestructive however which makes it TOTALLY worth it.
reviving a zombie thread, I came across this post hanging around, and found it very very interesting.

I think that just a couple of diodes across C25 would do the job, maybe leaving D7...D10 where they are (in analogy with OD3 schem, where there are 2 diodes (D9, D10) on the input of the discrete opamp that has the clipping on the feedback loop, so the config would be almost the same).

I have to try.

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Post by Ben N »

Hmm, that does sound interesting. Might also be interesting putting LEDs in the FB loop and leaving small signal diodes or schottkys to ground, or vice versa, to set the order of clipping.

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Post by Beedoola »

Effectsiation wrote: 01 Dec 2010, 22:25
floris wrote:This is what I have stored as being "Keeley Boss BD-2 mods":

===

Keeley BD-2 standard + phat mod:
https://www.diystompboxes.com/smfforum/ ... ic=44746.0
C1, C15, C6, C13, C7 10UF TANTALUM (I had these)
C14, C34 .1UF METAL FILM
C36, C35 .047 METAL FILM
C20, C25 100PF SILVER MICA
C21, C23 47PF SILVER MICA
C22 220PF SILVER MICA
C100 (ON TONE POT CIRCUITBOARD) .033UF, .068UF
D9 – install jumper
This is what I was looking for that mentions all the caps (it was C35 &C36 missing, which are the Box Film capacitors at .047uf), and adds up with what the kit has (minus all diodes, but taking that info from the other post this should be everything) Thank You!

So just to reiterate I'd say this is the "complete" Keeley BD-2 Mod (w/Phat Switch)


D3 - Change 1SS133 to a 1N4002 diode for asymmetrical clipping. This adds second order harmonics. This adds to the tube type sound. I like the sound of this change.
D7, D8, D9, D10 - Change 2 of of these diodes from 1SS133 to a single 1N4002. More second order harmonic distortion. Although the change is slight, I like it. We actually take out one of the two pairs and replace it with a single 1N4001.
C1, C6, C7, C12, C13, C15 - Change to 10uF Tantalum capacitors.
C14, C34 - Change to 0.1uF metal film capacitors
C20, C25 - Change to 100pf Silver Mica Capacitors
C21, C23 - Change to 47pf Silver Mica Capacitors
C22 - Change to 220pf Silver Mica Capacitors
C35, C36 - Change to .047uf Metal Film Capacitors (box-style)
C100 (located on Tone Pot Circuit board) - Add a SPDT switch to flip between 0.033uF metal film capacitor and add a 0.068uF metal film capacitor in parallel with this value for Phat Mode
Can someone explain the second step with the D7-10 diodes.

Are you supposed to replace any of the two out of the four with 1N4002? And at the end it says "we like to take out one of the pairs and replace with a single 1N4001" Would that be D7/8 are 1N4002 and either D9 or D10 is 1N4001?

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Post by The G »

Beedoola wrote: 06 Apr 2021, 03:00
Effectsiation wrote: 01 Dec 2010, 22:25[...]
D7, D8, D9, D10 - Change 2 of of these diodes from 1SS133 to a single 1N4002. More second order harmonic distortion. Although the change is slight, I like it. We actually take out one of the two pairs and replace it with a single 1N4001.
[...]
Can someone explain the second step with the D7-10 diodes.

Are you supposed to replace any of the two out of the four with 1N4002? And at the end it says "we like to take out one of the pairs and replace with a single 1N4001" Would that be D7/8 are 1N4002 and either D9 or D10 is 1N4001?
That clipping stage uses D7+D8 on one side as a clipping unit and D9+D10 as the other. This appears to be an attempt to get more of an asymmetrical clipping by replacing only one of the two units, so it means to either
- replace D7 and D8 with a single 1N4002 or
- replace D9 and D10 with a single 1N4002
Like this
bd2_diode-mod.png
bd2_diode-mod.png (13.33 KiB) Viewed 4375 times
bd2_diode-mod.jpg

...IF yours have a pre-2017 PCB :lol:
bd2_after-and-before-2017.jpg


Remember to check the diodes polarity.

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Post by Beedoola »

Ok, so two of the original 1SS133 stay in place?

I see it says "jumper D9" so I'm assuming D10 was the one that had the 4002.

Also, for the C100 cap and additional caps. Is c100 supposed to be left in place and then the switch two the two caps is added? or the .033 replaced the C100 cap and the .068 is on the switch?

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Post by The G »

Beedoola wrote: 06 Apr 2021, 05:03 Ok, so two of the original 1SS133 stay in place?

I see it says "jumper D9" so I'm assuming D10 was the one that had the 4002.

Also, for the C100 cap and additional caps. Is c100 supposed to be left in place and then the switch two the two caps is added? or the .033 replaced the C100 cap and the .068 is on the switch?

It doesn't matter which of the D7+D8 or D9+D10 pairs you replace, as long as you keep the polarity right. I chose the pair which seemed further away from other components, thus easier to desolder.

For the tone mod I would use a SP3T on-off-on switch to add a 22n or a 100n capacitor in parallel to C100. This way I'd be able to switch from original seting in the middle position of the switch to 32n or 110n. Given the tolerances of the ears and capacitors, the exact values are not that important.
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centre-off_toggle_switch.jpg (6.64 KiB) Viewed 4371 times

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Post by Beedoola »

So I’m still confused from what has been said by Keeley. Is C100 supposed to be completely removed and it’s just either the .033 or .068 on a switch?

I left C100 in and it’s too bassy

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Post by The G »

Think a bit about it. You have the original C100 of 10nF, then you add a 33nF and a 68nF into the mix. Available combinations are: 10nF (original), 33nF, 68nF, 43nF (10+33), 78nF (10+68) and 101nF (33+68).
Apparently, the mod you're talking about replaces the stock 10nF C100 with a 33nF capacitor and a switchable 68nF in parallel with that. So 33nF and 101nF.
The mod I proposed above keeps the original 10nF, with switchable 22nF and 100nF capacitors added. So 10nF, 32nF and 110nF. So it keeps the original value, adding two options that are close enough to the mod you're talking about (the differences are smaller than the capacitors' normal tollerance range).

BUT, as with any mod, use your ears and common-sense. If it's too bassy, decrease the capacitor ¯\_(ツ)_/¯.
Or, if you need/like only one capacitor option, discard the others - just replace C100 with whatever value you like.

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Post by DrNomis »

I'm currently doing some maintenance work on my Boss BD-2 Blues Driver, just swapping-out the old in/out sockets for some new ones, and giving it a general clean-out.
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.

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Post by Ben N »

Hey, Doctor, I recently replaced the switch on mine. Easy-peasy. These pedals are not only well-built, they are easy to maintain.

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Post by Paul_5 »

I’ve just built one on veroboard and live the clarity, but not the fuzzy, brittle top end.

I USDA’s a dpdt on/off/on switch n parallel with c100, which I changed to 33n, I also put a 33n on one side of the switch and a 68nf on the other side, so I can choose between c100 being 33, 66 or ~100nf.

I’m also going to swap out the 10k linear pot for a logarithmic one to give me more control over the bassier end of the sweep.

Changing the dual gang drive pot for two singles means that I have a clean boost and a dirty boost, so I can dial in the right amount of grit.
The sounds in my head don't match the sounds from my amp, I guess that's why I'm here...

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Post by Intripped »

when i needed it, i couldn't find a clearly readable schematic of the BD-2, so i've done it;
there's also the PCB silkscreen, here it is:
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Post by modman »

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