Boss ROD - 10 Overdrive/Distortion/Fuzz

[WGTP]

Just bought one I found on the internet for $65.  I think they have been out of production for some time.  Boss has been using discrete op amps for over 20 years.  The schematic has 1986 on it.  This is a very interesting pedal for several reasons.  It has 4 different OD/Distoritons that are all discrete JFet/BJT op amps; I BJT Fuzz (let me know if you recognize it); each is voiced differently to increase the differences between them.  3 band EQ with variable mid frequency; and line out has an op amp speaker simulator; 1/2 rack size.  Lots of circuit snippets.

http://www.aronnelson.com/gallery/main.php/v/KHE/Boss_ROD10_Schematic.jpg.html?g2_imageViewsIndex=1

[Mark Hammer]

I bought one for a song last year or so also.  Not God's gift to fuzz, but an interesting assortment nonetheless.  Take a look at the Blues Driver schematic and a number of Jay Doyle's circuits that rely on discrete op-amp configurations.  A lot of similarities there, and a great areana for learning what circuit tweaks produce what audible outcomes.

I also draw your attention to OD III, which has a 5.6V supply voltage, in contrast to the 8V supply voltage that the other four modules have.

Hmmmmmm......

[rnfr]

is that a superfuzz i see?  just a guess...

[DougH]

No, those diff amps are part of the discrete op amp part of the circuit. If you look at a superfuzz schem, the collectors of the 2 diff amp xsistors are tied together for producing the octave.

[Dragonfly]

Interesting...the fuzz is in the Ibanez Standard Fuzz / Kay Fuzz family. Different values but a similar topology.

I've had the schemo for a while but I never really looked it over - some interesting circuits in there.

[WGTP]

I think Mark is the one that first mentioned it a while back.  I hadn't noticed that the ODIII was operating at a lower (5.6v) voltage.  This works well with my Valve Jr. since it has no tone controls.  The Fuzz is pretty thin and nasty, compared to the others.  The OD I has the SD-1 diode arrangement and the ODII the Tube Screamer.  The midrange frequency control demonstrates how important the midrange EQ is to the overall character of a distortion.  I'll have to compare it to the DS-1, etc. to see if the discrete op amps are smoother than standard ones.   

[Mark Hammer]

Well, here's a suggestion to owners of a Boss BD-2.  Stick a couple of diodes in series with your battery to drop the voltage, or just score a suitable zener and run it from V+ to ground, and see if you get something interesting by working with a reduced supply voltage.  That'd actually be kinda neat if you could squeeze a different personality out of the pedal for the addition of a zener and a SPST toggle.

[WGTP]

Cool idea.  The OD-3 (different second stage) and MD-2 (that output stage is a b****) also uses a similar op amp set up.