Question about MXR distortion+ schematic

[Ghost Planet]

I found this MXR distrotion + schematic that has some really cool mods I want to try. I just have quick question about the schematic. R5 has a 1M value, and under the resistor it says 4.5v. Does this mean you connect the 9v power supply here as well as pin 7 on the IC? Is 4.5v the voltage after it passes through the 1M resistor?

[Govmnt_Lacky]

The 4.5V is most likely the BIAS voltage. This is created from the 9V input and is used to bias the op amp and other parts of the circuit.

Link to schematic to verify??

[Ghost Planet]

Here's the schematic, sorry I forgot to post it.
http://www.premierguitar.com/Magazine/Issue/2008/Dec/MXR_Distortion_Plus_Mods.aspx

[Govmnt_Lacky]

That is only a PARTIAL schematic of the circuit. That schematic DOES NOT show how the 4.5V Vref is created.

Here is a better "stock" schematic that shows how to get the 4.5V:

http://www.generalguitargadgets.com/pdf/ggg_dist_plus_sc.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Good Luck 

[Ghost Planet]

Not cool, don't post a partial schematic, it leaves us newbies scratching our heads. Thanks for the help.

[Steve Mavronis]

Here's a re-drawn schematic that I made of a 1976 MXR Distortion+ based on a MXR factory schematic diagram. I find it interesting how manufacturers style the layout of their products vs user traced schematics from studying pedal circuit boards and wiring:



And here's a scalable PDF version of the same good for printing:

http://home.comcast.net/~snmavronis/mxr_dist+_schem.pdf

[Govmnt_Lacky]

Beat you to it Steve! 

Just PM'd a link to your D+ thread.

[Steve Mavronis]

Beat you to it Steve! 

Just PM'd a link to your D+ thread.

Thanks!