OD03... help about true bypass?

[Gilles C]

Everytime I look at a circuit from a BOSS pedal or any other brand having FETs to do the switching, I wonder about something...

Take for example this OD-3 schematic.

http://www.diystompboxes.com/cgi-bin/webbbs_scripts/webbbs_config.pl?read=296

If I want to bypass the Q9 FET that is one of the FETs that does the switching for the bypass.

C21 is 1uF and C29 is 0.018uF, so if I take R44, R45 and Q9 out of the circuit, what should be the value of the coupling capacitor I will keep?

1uF or 0.018uF? Or something in-between?

And it's the same at the output. Should I use 1uF or 10UF if I take R10, R22 and Q4 out?

See what I mean?

And please, don't tell me to use my ears and use whatever sounds good.  :wink: , I would prefer an answer based on calculations or logic.

Thanks...

Gilles

[Kleber AG]

Hi Gilles,
I'm sorry I can't help on cap values calculations...
But what are you planing to do? Modify it to true bypass?

Well if so, I think that Q8 and Q10 would turn out as redundant as they both are working as buffers? I'm not sure, but maybe it'd be a good idea to keep only one of these buffers, no?

I wonder about installing 3pdts on my boss pedals too...
Do you know if it could be fisically placed at the same place as the plastic switch actuator at boss pedals, and still have the whole pedal case to actuate on the 3pdt as crybabys do?

Sorry if I'm messing the thread Gilles.
Best regards
Kleber AG

[Gilles C]

No problem, you're on the right track...

Except that I could build a clone in another box before I do anything on the original.

I like to keep it on the safe side first.

About the 3PdT switch, I saw a pic some time ago of a BOSS pedal that someone modified to accept such a swcitch.

He just replaced the moving part with the rubber by a bakelite plate, and fixed the 3PDT footswitch on it.

About Q8 and Q10 being redundant, I just noticed that something must be missing... That's why there is a buffer at the input. When Q9 is open (Hi-Z), another FET must bring the output of the input buffer to the output buffer.

I only looked at the circuit configuration itself and didn't noticed that.

Hummm... Let's check another schematic...

OK, like in this one

http://www.diystompboxes.com/cgi-bin/webbbs_scripts/webbbs_config.pl?read=180

But without the FET switching, you're are right, it would be possible to take the input buffer out because (except for the input impedance which should be different) it wouldn't make any difference I think.

Gilles

[Kleber AG]

OK, uhmm
From the first schem you posted I would keep the first buffer as it's biased for around 1M input Z and remove the second buffer.
Again from the first schem posted (maybe the second too) I think it would be worth to even try to remove that output buffer after the output volume.

For the 3PDT change, would it be possible to make it actuate like the Wahs enclosures do? But with the boss standard enclosure_cover? It looks to be possible to fit the 3pdt in place of that plastic mechanism actuator that boss uses.

Anyone has any experience on this? Before I start something? :lol:
Thanks Gilles!
Kleber AG

[Joep]

Hi Gilles,

For the input you can remove R44, R45, Q9 and C21. Make sure you connect C29 to the source of Q8.

For the output remove R22, R10, C6 and Q4. Again make sure you connect C12 to the base of Q1.

You can actually use the standard Boss style Flip-Flop circuit, to drive a Relay (through a transistor). Wire the Relay like a DPDT footswitch and you are ready.

Bye,

Joep

[Ansil]

Yes people i keep posting this but i guess i am one of the few to try it. all standard boss pedals will accept the tpdt carling.   u will ahve to adjust the nuts on it to make it set right and to ge the throw with the lever action of the pedal, bt i did this with my od 1 years ago as well as my boss HM pedal

u do however need to take the lid off to get it set up right if you ahve big hands though as its easier
giles man i would just leave both the caps as they are both there i see no reason to remove them just yank out the fet, and jumper it.

that is what i do on nearly all my boss pedals.

[Gilles C]

OK, thanks guys.

That will do it.

Both for the Carling switch and the parts values.

Gilles

[modmod]

Yes people i keep posting this but i guess i am one of the few to try it. all standard boss pedals will accept the tpdt carling.   u will ahve to adjust the nuts on it to make it set right and to ge the throw with the lever action of the pedal, bt i did this with my od 1 years ago as well as my boss HM pedal

u do however need to take the lid off to get it set up right if you ahve big hands though as its easier
giles man i would just leave both the caps as they are both there i see no reason to remove them just yank out the fet, and jumper it.

that is what i do on nearly all my boss pedals.

do you mean using 3pdt carling  for true bypass ? where can i get those 3pdt carling ? also does it mean boss pedal  with true bypass without drilling hole ? thanks

[Ansil]

yes


i a going downstairs now and take a picture for everyone and do a tutorial  be right back

[Eric H]

About the 3PdT switch, I saw a pic some time ago of a BOSS pedal that someone modified to accept such a swcitch.

He just replaced the moving part with the rubber by a bakelite plate, and fixed the 3PDT footswitch on it.

Gilles

Like this?
http://users.abac.com/ehensel/stompbox/pedals/trem2.jpg

That's a (spst) switch from a vacuum cleaner that controls a relay :-)
I think Ansil's right --a tpdt could be installed  and controlled by the foot-pad.

-Eric

[Ansil]

oh god that pic was bad.. lol but did one like that years ago with a broke boss ce2 as i didnt' have the means to fabricate then..

http://geocities.com/austenfantanio/boss.htm

heres the quick tutorial i got oatmeal cooling so i had to do it quick

[Gilles C]

>Like this?
http://users.abac.com/ehensel/stompbox/pedals/trem2.jpg
<

All right  

So you're the one who did it...

>i a going downstairs now and take a picture for everyone and do a tutorial be right back<

A tutorial... great idea.

Although it's possible that I put it in another box for a while. I want to experiment with a PIC to control 2 or 3 BOSS effects in the same box.

1 switch with a sequence of sounds.

It will also be easier to mod the pcb(s) if I want to.

Then, it could go back into it's BOSS box.
(maybe...)

[Ansil]

well i didnt' do the trem pic but i did have a pic up for my old boss pedal but i dont' know where it is and well its gone now a modded ds1 well a ds386 now lol

[Kleber AG]

 I'm back home now...
Cool thread guys, thank you all, thanks for the guide Ansil...

uhmmm 5 pedals now to convert to true bypass  Cool...
I never liked them with all that stuff (buffers and all) always on my guitar path...

Awesome
Kleber AG
Yeah, I'm happy

[Mark Hammer]

Um, is it just me, or does that schematic HAVE no bypass?  I'm looking, and I see two FETs for cancellation, but I don't  see any signal path for what happens when the effect is cancelled.

[Ansil]

good one mark i jsut saw that too. and was like woahhhhhhhh

[Gilles C]

As I said in an earlier post, that schematic has the missing FET

http://www.diystompboxes.com/cgi-bin/webbbs_scripts/webbbs_config.pl?read=180