Question about Boss Super Overdrive schematic

[davidjnichols]

Hey guys.  I'm going to build a Boss Super Overdrive from this schematic.  I was wondering about the Dots instead of the regular grounding symbol on some points.  There is a note that says the dot means 4.5V bias.  I'm not sure what that means.  Does it mean the dots all connect to a different point than the common ground?  Thanks a lot for the help on the noobish question!

Here's the schematic:  http://www.co-bw.com/Guitar%20Files/Guitar%20Amplifiers%20-%20Overdrive%20&%20Distortion_files/a_bossod.gif

[jymaze]

Your schematic is missing the power section, where you would find a voltage divider going to those " points". I would not make a SD1 or a Tube Screamer since you may end  up spending way more money than just by buying one since they are so cheap. I would recommend a simple but boutiquy circuit, at least it is worth your time since you will actually save money making it yourself. An OCD overdrive for example would be a good choice.

[Govmnt_Lacky]

Does it mean the dots all connect to a different point than the common ground? 

That is CORRECT. 

In the schematic you linked, it DOES NOT show how the Vbias is generated. A common method for generating Vbias (4.5V) from a 9VDC source is to feed the 9VDC into (2) series 10K resistors going to ground. Tap your Vbias from between the 10K resistors.

9VDC------- 10K------.------ 10K-------------- GND
                              1
                              1
                              1
                           Vbias

[davidjnichols]

Does it mean the dots all connect to a different point than the common ground? 

That is CORRECT. 

In the schematic you linked, it DOES NOT show how the Vbias is generated. A common method for generating Vbias (4.5V) from a 9VDC source is to feed the 9VDC into (2) series 10K resistors going to ground. Tap your Vbias from between the 10K resistors.

9VDC------- 10K------.------ 10K-------------- GND
                              1
                              1
                              1
                           Vbias

Okay, so there's a 9v+ going to the transistor.  If I were building this, would I go from my 9v power source to the transistor and also from 9v to 10k resistor to vbias to 10k resistor to ground?  And could I have all 4.5v bias points meet at that same junction?  Like this...

9v ---.---------------NPN
        l
        l---10k----.----10k----GND
                       l
                       l
              all 3 vbias points?
                       

[caspercody]

Don't forget to put 9 volts to the IC chip. Your bias looks correct, but might want to add some caps for noise reduction. Just look for a schematic for a Tube screamer (looks to be similar to that), and look at the power supply section.

[davidjnichols]

Don't forget to put 9 volts to the IC chip. Your bias looks correct, but might want to add some caps for noise reduction. Just look for a schematic for a Tube screamer (looks to be similar to that), and look at the power supply section.

Thanks.  It makes a lot of sense now.  For the IC, this pinout should be correct?  (are most 8-pin IC pinouts the same?)  http://pinout-circuits-images.dz863.com/6/RC4559.jpg

Pins 1-3 are shown on schematic, pin 4 is ground.  On the other side, pins 5-7 are shown and pin 8 is 9v+? 

Also, this Jack Orman TS schematic shows the power section just as you guys described, and he has a 47uf cap for noise.  If I built from this schematic, I'd simply connect all the V+ points to the V+ part of the power section and the Vr points to the Vr part of the power section?   http://www.muzique.com/schem/ts808.gif

Thanks again, guys.  I've built quite a few tremolos, ABY switches, effects loops, line boosts, & fuzzes, but this is my first real attempt at something with more than one voltage and an IC.

[caspercody]

Here is a great little article about what that distortion circuit is doing:

http://www.generalguitargadgets.com/richardo/distortion/index.html

Pins 1-3 are shown on schematic, pin 4 is ground.  On the other side, pins 5-7 are shown and pin 8 is 9v+?  Yes

If I built from this schematic, I'd simply connect all the V+ points to the V+ part of the power section and the Vr points to the Vr part of the power section? Yes

[Govmnt_Lacky]

Pins 1-3 are shown on schematic, pin 4 is ground.  On the other side, pins 5-7 are shown and pin 8 is 9v+?  Yes

If I built from this schematic, I'd simply connect all the V+ points to the V+ part of the power section and the Vr points to the Vr part of the power section? Yes

Yes!