Hey guys,

I made some changes on my Blues Driver the other day and I'm way happier with it now than I was...  I always liked it in front of a crappy SS amps but now it sounds good in front of tube amps too.

I searched the archives here and found a list of the "Keeley mods" and tried a number of those.  My major complaint with the BD-2 in its stock form is that it's just too friggin' bright and middy (and I use humbuckers and old-Marshall type amps.)  

I ended switching the input cap to a .22 and changed the cap that connects to the hot lug of the tone pot to a .033.  I was surprised that I still had the tone control cranked hard left and it was still too midrangey!!!

Earlier in the circuit there's a tonestack that resembles the typical old Fender tonestack and I noticed the midrange resistor is 15K.  I put some jumper leads on that resistor and paralleled in a 2K2 for giggles.  Much better!  I can actually turn the tone control up some now!  I ended up replacing that 15K (R51) with a 50K trimpot (all I had on hand that was physically small enough), and dialed it most of the way down.  I figured having a trimpot there was the best approach - it allows for a little flexibilty.  As the top end of my hearing continues to go I can gradually crank the trim pot up.  

Thought this might be helpful to someone!

Jim

Sounds cool!  I've been modding the heck out of my BD-2, did most of the Keely mods in addition to some that I found on www.indyguitarist.com.  

I'll have to give these a whirl.  What are the locations of some of the components you're tweaking ("input cap" etc.)?

\m/

Hi Danny,

Are there mods posted at the site you mentioned?  I couldn't find any...

The Boss factory schematic is posted over at www.generalguitargadgets.com so you can check out the part numbers.  http://www.generalguitargadgets.com/v2/boss/BossBD-2.gif

The input cap is C14.  The tone control cap I changed is C100 and the "midrange resistor" is R51 on the drawing.

How do you find your Blues Driver?  Am I the only one who finds it too bright?  

Jim

Hey Jim, does that use the Mitsubishi in-line 8-pin op amp? Similar to the DS-1.

IMO the SD-1 suffers from the same problem -it's got a real boxy mid range hump.

I wonder how you could fix that?

Hi Fret Wire,

I'm not sure of the number but yes, it does have an inline opamp.

Jim

It's my understanding that there is a JRC inline chip that is quite an improvement over the stock chips used in the BD-2 and DS-1. Supposedly Anolog Mike uses them in the DS-1. Originals were Mistubishi and later Rohm (proprietary), I believe. I've been trying to find info and data sheets on these JRC replacements, but no luck.

Jim--

You have to sign up to the IndyGuitarist newsletter, then they immediately send you a link for the mods.

In general, I'm more pleased with the way my Blues Driver sounds now.  However, yesterday I installed the Keely "phat switch" mod, and I guess I did something wrong, because at practice last night the signal would only go through the pedal when it was on--having it off meant no sound, and I don't think the switch was working either...  crap.  I tried it out at home and it seemed fine..?

The opamp in the BD-2 is not really doing all that much.

It is buffering tha bias power supply and is just a non-inverting amplifier in a filter that uses a simulated inductor.

The majority of what is going on in there utilizes discrete opamps.

The midrange problem you guys hear can probably be most efficiently meddled with by swapping out different values for C9 and C16. These set the resonant frequency for the simulated inductor and C9.

You may also want to mess with the filter network before the diodes to ground.

Jay Doyle