Boss - BD-2 Blues Driver 1995  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
Post Reply
User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

matt239 wrote: Can you explain this a little more? - I don't understand this part of the circuit too well. :oops: - :scratch:
- R31, R34, R32, R25 look to me like they go from signal to ground so that decreasing them would reduce gain, rather than increasing them. - I'm sure I just don't quite get it. - I'm obviously missing something. :oops:
- OK so R31+C22 (along with VR1A, C23, R29) are part of the negative feedback loop right? by removing highs from the negative loop, it actually boosts treble/cuts bass through the section right? - Or is that backwards? Ackk!
_________________________________________________________________________

- Would lowering R1 & increasing R3 get us a little more output without trying to raise the gain in IC1B? or is this a bad idea?
- &/or, if we've reduced gain in the earlier sections can the gain of IC1B be increased w/o "splat"?
___________________________________________
- Sorry for so many posts; I didn't think of everything all @ once, & then it was too late to edit my earlier posts, & put all my questions in one.
I'm just trying to figure this out.. :scratch:

User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

OK. I've made a lot of changes. (I'll list them if somebody wants to see them.) I like the sound of these changes a lot. It sounds really good "clean," it sounds really good cranked, & it has a very nice sweet semi-clean sound, BUT, there is still a little bit of splat/sputter at the very end of a long chord.
Can you guys help me figure out how to eliminate this? Here's my thinking so far:

-I believe I have eliminated the I.C. section as a potential source of the sputter. If the gain is @ a middle position, the sputter remains @ any setting of the volume control. - I have reduced gain through the first two sections significantly, which has reduced, but not eliminated sputter, which leaves me thinking:

A: The transistors in the first stages aren't biasing correctly??
B: One or more of the transistors is damaged??
C: It's just the diodes to ground? Maybe they can only be clean/distorted/more distorted, but can't turn on/off that smoothly??

I'd love to get your guys' input.. Anybody?

(Has anybody run the pedal with the clipping diodes completely removed? How did that sound?)

User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

It wasn't the diodes. - Not I.C. - It's the trannys.

User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

OOPS! HELP!
OK. I was trying one more mod, & now I can't get the pedal to work.
I changed C24 to 0.1uF (R34 has already been made 10k)
Changed R9 to 10k (from 6.8k)
I believe R9 is the feedback resistor on the IC op amp. (not R8, as some schems here have it..)
I have checked my joints, & re-done them. I've tried three caps @ C24, & now have original cap back in.

Can R9 not be 10k? Am I confused about what it is?
Have I cooked the IC?
Where should I start? -Any advice will be much appreciated.
Thanks.

User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

I've continued my request for troubleshooting help here: viewtopic.php?f=54&t=11360&p=122934#p122934

On a happier note, in the meantime I picked up DS-1 for cheap, & made some minor changes, & it sounds great! :)
I'm sure with a little help I'll get the BD2 back up & running..

in the meantime I'll try to clarify what I was reporting before; - I ran the pedal with the diodes lifted, there was plenty of distortion & a lot of splat!
it seems to me that the diodes actually help to smooth out the distortion in this circuit. This seems to be the case in the DS-1 also.
My strategy has been to reduce some bass early in the circuit (I was boosting it, & it was already boosted by Keely, decided to reverse some of that..) & to boost bass later in circuit, & to back off the gain early in circuit, & try for a little volume boost later in circuit. Seemed to be helping..
Now that effort will just be on hold a little while till i fix what I've broken..

User avatar
Effectsiation
Information
Posts: 42
Joined: 09 May 2008, 18:18
Has thanked: 7 times

Post by Effectsiation »

Sorry to bring up an old topic, but does anyone have a full list of all the changes Keeley does to a BD-2? Here's why I ask, a friend sent me this link: (https://cgi.ebay.com/ws/eBayISAPI.dll?V ... TQ:US:1123) Asking me if I could help him perform the mod if he bought the kit. I'm looking at the kit and I count:

5 Radial Silver Mica Caps
5 Radial Tantalum Caps
4 Radial Film Caps
2 Radial Box Film Caps
2 1N400X Diodes
1 3mm Clear Blue LED
1 SPDT Switch
Red Wire
Green Wire
Heatshrink

So... by everything I've previously read about the Keeley Phat Mod, it is usually described as this:


D3 - Change to 1N4002
D7, D8, D9, D10 - Take out one of the two pairs of diodes and replace it with a single 1N4001
C1, C7, C6, C12, C13, C15 - Change to 10uF tantalum
C14 - Change to 0.1uF
C100 - Install switch to go from 0.033uF and 0.068uF cap in parallel with this value for the Phat Mode
All ceramic caps - Change to Silver Mica

I could be daft but that still leaves 2 caps missing from the mod instructions I've seen... maybe the 2 Box Film ones? Anyone know where these might go? I did read previously in the thread that the whole mod hasn't been captured, maybe we can finally capture it?

I just don't want my friend buying a kit from some guy making a quick buck when I can just tack the stuff onto my next Small Bear Order and help him out.

User avatar
floris
Cap Cooler
Information
Posts: 473
Joined: 14 Oct 2007, 12:05
Has thanked: 231 times
Been thanked: 72 times

Post by floris »

This is what I have stored as being "Keeley Boss BD-2 mods":

===

Boss BD-2 Mods by Keeley

viewtopic.php?f=11&t=1062&start=0
http://www.stevesmusiccenter.com/KeeleyBD2.html
Although I don’t own a BD-2 any longer, I could probably kick myself for letting it go after playing a modded one. Stock it’s a good sounding pedal but once you apply some mods to it, such as what Robert Keeley has done, it’s like an entirely new pedal altogether. Now I want one again. Below are some mods that you can do to your BD-2 provided by Mr. Keeley himself.

This is not all-inclusive in what can be done to the Blues Driver. It is meant to give an idea of where the tone can be improved or changed. All of the changes are subtle but when packaged together offer a nice improvement.

* D3 - Change this 1SS133 to a different (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 and 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, C7, C6, C12, C13, and C15 - Change this electrolytic capacitor to a 10uF Non-polarized caps. Non-polarized caps sound better . I like these anywhere there is signal coupling at this high a value.
* C14 - Increase input coupling capacitor value to 0.1uF for increased bass response from your guitar.
* C100 (18nF) - Here is where we can affect the tone control. I prefer a little more lower-midrange and bass frequencies through the tone section. You can increase the lower frequencies by increasing the capacitor value to 0.033uF. Install a switch to add a 0.068uF cap in parallel with this value for the Phat Mode! Flo: Perhaps even increase it to 82nf up to 220nF.

Most of the ceramic caps are changed to Expensive Silver Mica (available through Small Bear Electronics http://www.smallbearelec.com or http://www.mouser.com or http://www.digikey.com). This is what makes our mod sound so good. A noticeable reduction in noise. An increase in the smoothness and no harshness left. This type of upgrade is not found in anyone’s mods. The best sound is right here.
===

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

User avatar
Effectsiation
Information
Posts: 42
Joined: 09 May 2008, 18:18
Has thanked: 7 times

Post by Effectsiation »

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

User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

I've got the parts in & I'm going to try to repair my BD2 today, starting with Q13, then the IC. I'll report the results. Wish me luck!

In any case, will these mod values work?
R34 10k
C24 0.1uF
R9 10k

User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

I fixed it! :D
- & the new values work. - It sounds REALLY GOOD, but still has some splat on the decay..

User avatar
gurishka
Breadboard Brother
Information
Posts: 86
Joined: 22 Oct 2008, 02:34
Location: Victoria, Australia
Has thanked: 23 times
Been thanked: 1 time

Post by gurishka »

Can anyone give me advice on C100 and C101. There are various thoughts on what to change and so forth. Some say change C100 and some say change C101. Both are the same value stock. But what if I changed them to the fat mod and used a dpdt to switch between the two. Will it change it too much?

User avatar
MoonWatcher
Diode Debunker
Information
Posts: 715
Joined: 28 Jul 2008, 12:27
Has thanked: 40 times
Been thanked: 52 times

Post by MoonWatcher »

gurishka wrote:Can anyone give me advice on C100 and C101. There are various thoughts on what to change and so forth. Some say change C100 and some say change C101. Both are the same value stock. But what if I changed them to the fat mod and used a dpdt to switch between the two. Will it change it too much?
Grab a schem of the OD-3.

It uses a .033uF and a .022uF - IMO, Boss got it perfect with that pedal, so just match it with the BD-2. You want the smaller cap going to ground, just like the OD-3.

User avatar
Diego
Information
Posts: 3
Joined: 02 Jan 2011, 03:25

Post by Diego »

matt239 wrote:I fixed it! :D
- & the new values work. - It sounds REALLY GOOD, but still has some splat on the decay..
Hey Matt, what did those resistor and cap values you changed do to the sound?
I'm halfway through modding my BD2 and all info is welcome. Thanks! :D

User avatar
matt239
Solder Soldier
Information
Posts: 228
Joined: 11 Sep 2010, 18:54
Has thanked: 60 times
Been thanked: 5 times

Post by matt239 »

R34 changed to reduce gain (& distortion). C24 changed to keep filtering roughly the same through that section.
R9 changed to increase gain of op-amp. There seems to be a lot of clean gain available there..
My pedal already had the Keeley mods, & I changed the "Bassman style" EQ to be much flatter, & the clipping diodes are all now 1N34 germaniums.
It's much cleaner/softer now. I'm trying to get it to give me a range of semi-clean tones w/o "splatty" decay.
- Have had some success, but still a work in progress..

User avatar
Barry
Information
Posts: 5
Joined: 24 Aug 2008, 12:15

Post by Barry »

Anyone familiar with the Machine Head Pedals mod for the BD-2?

Barry

User avatar
okgb
Diode Debunker
Information
Posts: 768
Joined: 16 Mar 2010, 03:58
Has thanked: 226 times
Been thanked: 38 times

Post by okgb »

Anyone know of pcb's made for the blues driver ?
I'll go through the thread and look for a vero as well , tia

User avatar
jb351
Breadboard Brother
Information
Posts: 119
Joined: 14 Jun 2009, 12:27
my favorite amplifier: Traynor
Completed builds: lots
Location: Nova Scotia, Canada
Has thanked: 92 times
Been thanked: 17 times

Post by jb351 »

okgb wrote:Anyone know of pcb's made for the blues driver ?
I'll go through the thread and look for a vero as well , tia
Gaussmarkov has a layout to make your own.

http://gaussmarkov.net/wordpress/circuits/blues-driver/

User avatar
Thaxt
Breadboard Brother
Information
Posts: 65
Joined: 17 Jun 2008, 12:13
Has thanked: 1 time
Been thanked: 2 times

Post by Thaxt »

As with just about any distortion circuit mod involving diodes, builders should keep on hand a printout of all the AMZ/Muzique "Simple Mods" & diode mods. I do, & have found the diode mods - changing types, varying configurations, & definitely, placing variable resistances between diodes & ground , or diodes within feedback loops, open up a whole world of timbre variations in themselves.

Great stuff w a BMP or FTM too....there are endless diode alterations one can tinker around with.

I have heard a BD-2 driven into an actual late 50's Fender amp by one open mic player a few years back, & it was the closest thing I've heard yet to a classic Carlos Santana sustain & tone.

User avatar
dta74
Information
Posts: 17
Joined: 19 Mar 2011, 14:05
Completed builds: Jack Orman's Mini Booster
Jack Orman's MOSFET Booster
Boss DS-1 - several versions
Boss BD-2 - several versions
Ibanez TS-9 - several versions
Vox/Crybaby wahs - several versions

Post by dta74 »

First and foremost, full gut shots (by me) of a 2007 Keeley Phat Mod version:
https://picasaweb.google.com/1128180730 ... vNqom6POGQ

Second, a link to a demo video follows (excuse the horrible playing - sitting on the floor after a few drinks...). However, my approach to a demo video is different than others I usually see. I set both pedals with gain and tone knobs at 12:00, then set volume knobs for unity (approximately the same volume engaged as bypassed). Tone knobs on the amp were also set at 12:00 and the tone knob on the guitar was at maximum. Only control changed during the demo was guitar volume. While it can be said that due to component variability, 12:00 on one knob on one pedal may not be the same as 12:00 on the same knob on a different pedal, at least the knob is in the theoretical middle of the range of travel. More importantly, with each pedal set (theoretically) the same, the differences in the 2 becomes more apparent.



Third, being bored, having some OCD tendencies and too much time on my hands, I rifled thru this thread, Keeley's home page, Wampler's articles on premier guitar and a few other now-forgotten sites - compiling a list of mods. Came up with something like 8 different versions. Charted on a spreadsheet and looked for similarities. My 1st attempted was based mainly on someone's post of the "alleged" monte allums mod. Also, I was working from the scan of the original Boss schematic, NOT the redrawn version.

Component changes as follows:
R21: 2.7k
R34: 5.6k
R38: 220k
C8: 0.0047uF (472)
C14: 0.1uF (104)
C16, C17, C18, C27: 0.01uF (103)
C34: 0.082uF (823)
C35, C100: 0.047uF (473)
C101: 0.047 (473)
D3: 3mm red LED
D9, D10: 5mm clear lens red LED (1 for each diode)
Desistors were 1/4 watt, standard tolerance, caps were boxed poly film
I did not replace C1, C6, C7, C12, C13, C15 with tantalum or C20, C21, C23, C25, C26 with silver mica - mainly cuz I didn't have any on hand and didn't want to shell out the money and wait for em to arrive from Mouser.

First Impression: modded version had noticeably less gain & less output volume (knobs would need to be turned up 20-25% to equal stock version). It lost the upper mid peak and increased lower mids and bass, resulting in a "fuller" sound (mid peak change is almost like comparing a Vintage 30 to a GT12-75). Distortion quality was NOT as smooth as stock and had the "splatty" note decay that's been mentioned before. Overall, the pedal felt more dynamic and even more like an overdriven amp, than a diode-based pedal. Pedal cleaned up much sooner when rolling off the volume on the guitar. With Gain at 8:00 and volume up to compensate, the modded pedal became a pretty good clean boost. I'll throw it out there and say it was kinda like comparing an old Marshall SuperLead vs a JCM900 (which all had diode bridge-based distortion in their preamps).

Another thought on the splatty decay (the cause of which has probably been mentioned before): I've built several (nearly a dozen) of Jack Orman's Mini Boosters. Except for the one pedal where I clipped out C3 for less gain, all of em (especially when running on a battery) would heavily compress and lose volume then recover, when the knob was turned up well past 2:00 - evidence of the input signal exceeding the available power supply (think power supply "sag" on a tweed bassman). I'm theorizing that due to the fixed "fender-style" eq between the 2 gain stages, the resulting majority of low frequencies are hitting the 2nd gain stage en masse, overdriving the low end, resulting in the "splattiness." Turn the bass knob up on a Fender Twin and you'll get a similar effect - the low end gets loose and "farty."

So, I haven't actually had a chance to play the Keeley version yet... and it goes back to its owner tomorrow. But, I wanted to get gut shots while I had it. However, I'm sitting on 2 more stock versions, so one's gonna become a Keeley and another will become a complete franken-pedal.

Ideas floating around include the following:
Change components in fixed "fender-style" EQ - turn down the bass, go for a more neutral setting overall
Switchable diode/LED sections in D7-D8 or D9-D10 or perhaps a switch to lift the ground end of both sets (similar to the Turbo mode on the TS-9DX or the Comp Cut mode on the Fulldrive 2 - no diode clipping at all, just opamp gain)
Less overall bass boost throughout the pedal

Enjoy and feel free to laugh at my 1st attempt at a demo video...

User avatar
floris
Cap Cooler
Information
Posts: 473
Joined: 14 Oct 2007, 12:05
Has thanked: 231 times
Been thanked: 72 times

Post by floris »

Welcome dta74! A great first post and a good demo video to compare the two pedals imo. 8)
Perhaps some knob tweaking would have been nice to add to the video.
I actually liked the OD channel on the Peavey amp better than the pedals because they sound very shrill to me.

Post Reply