Help for my OD3 build

[junlokk]

Hello
I read you for a long time and now I want to start a build.
I hope you can guide me. Because I think the OD3 is difficult to understand.

I found 2 schematics :
http://www.freeinfosociety.com/electronics/schemview.php?id=2299
http://img392.imageshack.us/img392/4491/od3subclonebl3.jpg

The second seems too simplified (i don't want a subclone but a real clone), I want to be as close a possible to the original, but with a true bypass (I don't need the buffer circuit of the boss when it's deactivated)but maybe it is part of the tone when the pedal is ON ?

Can you help me I don't know where to start (what to dismiss in the schem)
Thank you.

[duck_arse]

hello and welcome, junlokk.

from the freeinfo circuit, you can drop Q9 across to the left, change R45 to 1M and send to ground instead of "VB". at the output, cut from Q4 to the right, and turn R22 to ground. the rest of the junk seems to be driving or boosting or clipping or toneing, so it would probably stay.

let us know how you get on.

[nocentelli]

I'll probably have a go at this tonight so I'll let you know how it goes. I'll probably use C29 as the input cap, and use everything from that point on to the volume control, maybe try the output buffer as well to see if it makes an audible difference. One thing that's not entirely clear from the axiom drift schematic, is that a single common node between R11, 12, 13 and 14 at the inverting input to the second opamp? It seems to be, judging from the convention used in the rest of the schem.

[duck_arse]

nocentelli - I'd say yes, single point. you get to work out whether R46 should become 1M or stay 100k. Q8 say 3.3Hz cutoff, but Q10 looks like 88Hz. will it make any much diff?

[junlokk]

Thank you very much !
I had a lot of work these days so I could not respond earlier

So it is :
IN--->r45(1M)to ground---> follow the rest of the schematics

I though we would keep the r42(10k) because it act as grid (very high frequency cutoff to avoid picking radio frequencies), or am I wrong ?

Thanks again for the help

[duck_arse]

R42 - good idea.

[junlokk]

Thank you man you are a great help

You said q8 is a high-pass filter at 3.3hz, and q10 is ALSO a high-pass filter at 88hz.
But do you know what is q9 and q4 doing ? and they are not grounded...

Also I don't understant a lot of guys said that all the boss pedals use a buffer when they are off (deactivated)
Is this buffer on the schematic ?

[duck_arse]

if you wander over to geofex and look for the technology of the boss bypass, or what it might be called, much will be made clear, he is an expert.

Q8 is the input buffer, high Z in, low Z out. it feeds the input bypass fet, Q9, which works best w/ a low Z signal. (Q10 is also a buffer, but with a much lower input impedance.) Q4 is the output bypass fet, driven from the signal at the level pot, and feeding the Q1 output buffer. when bypassed, both Q9 and Q4 go very high resistance, and pinch the signal off. there should be another linking the in and out that goes low resistance when bypass, allowing the input to get to the output.

[junlokk]

I am amazed that I understood everything you said (I'm not very good at electronic)
Very well explained ! Thanks a lot !

EDIT2 : After further thinking it is best to start a q10 like you said !!!!!
THANK YOU VERY MUCH 

[sanfi4u]

It seems Boss OD-3 Service Notes is the best kept secret in the world. I'm interested in the exact OD-3 schem (with power circuit, trigger etc.). Can anybody share one?

[Marcos - Munky]

http://experimentalistsanonymous.com/diy/Schematics/Distortion%20Boost%20and%20Overdrive/Boss%20OD-3.gif
Just missing the switch part, which is the same as other Boss stompboxes.

It's not that the service notes it's the best kept secret in the world. It's that this schematic have all the important info needed for repairs and to build a clone.