Boss Blues Driver

[nancyboy]

hey there, I'm new to here, but i wanted to know if anyone knew where to find the Blues Driver schematatic? I have seen it on the net before but i can't find it anymore.

Also a second question, is there a way i can increase the gain on this thing?

I have the pedal but it needs to be repaired and when i do so i'd like to make it as fuzzy as possibal.

[Peter Snowberg]

Welcome to the forum.

If you click on the schematic link at the top of the page and scroll down to Boss, you'll find the blues driver.

If you want even more fuzz, the first thing I would try would be to short one of the diodes shown in the lower left corner of the first page of the schematic. That will make the clipping asymmetrical which will liven up the harmonic content. I've never played with one so hopefully somebody else can sep in with some better ideas.

Take care,
-Peter

[Chris R]

this thread might help

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=16410&highlight=bd2

C

[nancyboy]

Welcome to the forum.

If you click on the schematic link at the top of the page and scroll down to Boss, you'll find the blues driver.

If you want even more fuzz, the first thing I would try would be to short one of the diodes shown in the lower left corner of the first page of the schematic. That will make the clipping asymmetrical which will liven up the harmonic content. I've never played with one so hopefully somebody else can sep in with some better ideas.

Take care,
-Peter

how would i short it out?, and would it for sure fuzz it out?
and also which one do i short?

Oh yeah does anyone have the official schematic. I am not skilled with schematics, and i just have to re-attach some wires on this thing, and it's hard to find them on the hand drawn one.

[Chris R]

http://www.generalguitargadgets.com/v2/boss/BossBD-2.gif

[petemoore]

I had one for a time. very subtle effect.  
 For hard distortion...try a Blackfire.
 Possible some diodes [try some configurations] and a cap to ground near the output, I would consider trying a different circuit for hard distortion tones.

[Peter Snowberg]

Out of that set of four diodes, you could short out any one of them and get the same effect. Just solder a little wire across the diode. That will cause the AC waves to get clipped at different voltages depending on whether the wave is headed up or down. You probably won't hear much (or any) difference between shorting a diode that is pointing one way or the other. If you want even more fuzz, you can change those diodes all day with different combinations of types and quantities. Right now it's got two Si signal diodes headed in each direction. Change 1 would be to eliminate one of those diodes so you have one pointed one way and two pointed the other. From there, try shorting another out so you have one pointed one way and one pointed the other (as in the MXD distortion+ & a zillion other pedals). From there, you could substitute one or two 1N34 Ge diodes for one of those Si diodes.

Each diode has a "forward voltage" which describes the point where it will start to clip the signal in a big way. Ge (Germanium) diodes like the 1N34 clip around 0.3V while the Si (Silicon) diodes clip at more like 0.5-0.6V. The lower the forward voltage is... the more clipping you'll see.

The stock configuration is clipping at roughly 1.1 Volts or so in either direction. Lets call that 1.1/1.1. Removing one diode by shorting will make that 0.55/1.1 or 1.1/0.55 depending on which side you short.

Using two Si on one side and a Si+Ge combo on the other will be more like 1.1/0.85. Two Si diodes on one side and two Ge diodes on the other will look more like 1.1/0.6. Using a single Si and two Ge diodes will be about 0.55/0.6. If you pull all the Si diodes out and use just two Ge diodes the figure will be more like 0.3/0.3 and you'll get TONS of clipping, but notice the smaller numbers... that will equal less volume so you'll have to turn the output level up to compensate for the volume drop.

As you can see there's a lot of experimenting you can do by changing diodes. The most common diodes used in clippers are 1N914/1N4148 Silicon signal diodes (same thing as the 1SS133 in the pedal), 1N34A Germanium diodes, 1N4001 Silicon rectifier diodes, and 1N5817 Schottky rectifier diodes. Try 'em all in singles and doubles for each side. Each sounds different. There are also LEDs, buy they have higher forward voltages still (more like 1.3 for a red LED) so that's not the direction you want to go in this case (they get crunchier rather than fuzzier anyway).

If you have the same combo on each side they’re clip symmetrically, which will give rise to more odd order harmonics. If you mismatch the diodes on either side, you’ll get asymmetrical clipping which will add more even order harmonics and a slightly “sweeter” tone.

The most fuzz you can get in that diode clipper will either be two 1N34s or two 1N5817s in inverse parallel (or a combo with one 1N34 and one 1N5817). Lots of boutique fuzzes have switches to allow for changing the diodes to alter the fuzz character.

I hope that ramble helped at least a little.

Now looking at the schematic (thanks Chris!), I would also try increasing the size of C27 (the cap right after the diodes) but a little bit. You'll have to experiment with sizes there.

Pete brings up a great point which is that you can only get so much out of a given design. Joe Davisson's designs are HEAVY.  :twisted: http://analogalchemy.com/

Take care,
-Peter

[Mark Hammer]

Whenever people say "I want more gain", I never know if they mean more volume or more distortion, since gain can produce either or both.

If it is harder distortion you want, certainly some of the suggestions made so far regarding the diodes are apropos.

If it is simply more output you want, you might consider raising the value of the feedback resistor between pins 6 and 7 on IC1B (the M5218).  It is currently 6k8, with a .0022uf cap in parallel.  If you increase it, you will raise the gain of that post-clipping stage.  However, to maintain the same bandwidth/rolloff you will need to reduce the value of the cap.  With a 6k8 resistor and .0022uf cap, the rolloff is set to start around 10.6khz.  If you raise the resistor to 10k, drop the cap value to .0015uf to maintain the same bandwidth.

You will note as well, that the drive control is a dual-ganged 250k pot.  This actually simultaneously sets the gain for each of two discrete transistor-based op-amp stages.  There may well be some interesting tonal ground to explore by un-ganging them and having dissimilar amounts of boost in each of these stages (e.g., max gain first stage, modest gain second.