SD-1 to OD-1???

[Regan]

Right, Thats that quad opamp, MartyMart! Those are the models I prefer.
Regan

[G Kresge]

In that case, does anyone know how to date Boss pedals based on their serial numbers? I'd love to locate one of those that you're talking about with the quad opamp!

[palthegiraffe]

And does anyone here have a schematic for the OD-1? The link in the schematics section of this website to that pedal goes to a nonexistent page.

[jplaudio]

[jplaudio]

[analogmike]

HI,

The older OD1s with the quad op amp were MUCH better sounding. You can get 90% of their tone on the newer OD1s with the following mod:

C1 C6 and C7 .047 -> .1
C2 .0047 -> .047

I have also removed the dual opamp and installed a quad but VERY difficult as they are in upside down and several traces need to be redone, and several bias resistors need to be removed or changed to run the op amp. The chip change did not help as much as the cap change.

have fun!

[G Kresge]

Okay, if the .01 is the less bright sounding of the two resistors that were suggested, what about metering the equivalent resistor in an OD1 and then placing a resistor of that value where the .01 is now in the modded SD1? If this would work, which resistor should I be metering in the OD1?

Analogmike: are your cap changes for the Od1, or for the modded SD1?

Thanks!

[G Kresge]

Also, I have a couple of different downloaded OD1 schematics, but I really don't know how to read them beyond recognizing what the parts are - no idea as to what the parts do or how they work together. If this would help out anyone that can make any suggestions about the mod, I could e-mail the schems.

Thanks again.

[analogmike]

Analogmike: are your cap changes for the Od1, or for the modded SD1?

Thanks!

Sorry I was unclear, the mod changes a later (8 pin chip) OD-1 to sound like the earlier (14 pin) OD1. But SD1 could be very similar to the later OD1, I have not compared them.

[Regan]

Thanks Mike,
I might try that if I don't end up finding an older model with the quad opamp, good to know I'm not nuts in thinking they are much better:)
Regan

[G Kresge]

Thanks for clarifying, Mike.

[G Kresge]

If the .01 is the less bright sounding of the two resistors that were suggested, what about metering the equivalent resistor in an OD1 and then placing a resistor of that value where the .01 is now in the modded SD1? If this would work, which resistor should I be metering in the OD1?

[bobbletrox]

Boss SD-1 schematic link
Boss OD-1 schematic link (4558C version with switching omitted from the diagram)

Call me cuckoo, but the only differences between the SD-1 and OD-1 according to the two schematics linked above are:

SD-1 to OD-1:
R1 >> 1K
C2 >> 0.0047uF
C6 >> 0.018uF
C4 >> 10K resistor (see below)

This last weird cap to resistor change requires a bit of extra trickery.  If you look at the second opamp stage of both pedals, you can see that:
In the SD-1:  
R7 is connected to pin 3, and 4.5volts is also connected to pin 3 via the capacitor C4.
In the OD-1:
R7 is connected to pin 2, leaving 4.5volts connected to pin 3 by itself via a 10K resistor.

I'm guessing you could solve this problem by doing this:
1. lift the end of R7 from its hole
2. desolder the wire from lug 3 of the tone pot
3. solder this wire to the lifted leg of the R7 resistor
4. swap C4 for a 10K resistor

Just make sure you're lifting the resistor leg that was leading towards C4 and pin 3 (maybe someone can confirm which side leg this is?)



Hopefully that trick should work.  Finish it off by desoldering the other two wires from the tone pot and put tape on the ends or something so they won't short out against anything.

I'm just going on the differences I can see in the two schematics and don't want to kill your pedal.  Perhaps some other forumites can confirm that this will actually work first?

[G Kresge]

I'll give that a try on another SD1 over the weekend. Thanks for the tips. I'll report back once I A/B that one!

[bobbletrox]

I think the end of R7 you've gotta lift is the leg pointing up towards the top of the board if I remember correctly.

I sure hope this works :twisted:

[G Kresge]

The .01 should give a lower cutoff on the high pass (more bass) than the .0047.
There may be other variables including the opamp.

Sorry, I'm unclear as to whether you're suggesting that I try using the .0047 to reduce the "brighter sound"? I'm not sure if I'm interpreting your post the right way.

Regarding the opamp(s):

The opamp in the OD1 (serial number 10200) which I really like the most of the OD1s I have is an NEC 4558C. I haven't gotten around to replacing the power adapter jack on this one for A-B purposes.

The opamp in the OD1 (serial number 0200) which I used for A-B purposes has a JRC4558D.

The opamp in the SD1 which I did the mod on is 4558DD. Is there *really* that much difference in the C, D, and DD suffixes? I guess that could be the case, since I don't know much about the subtleties of these things... Any suggestions or recommendations would be appreciated.[/b]

The "DD" op-amps are apparently the later re-issue version and sound a bit "crap"
They were the ones in my Park G10r amp, which i replaced with Panansonic NE5532's - IMO that made a HUGE difference to the tone and drive of that little amp.
My OD-1 is from 1979 ( 6800 ) and has a 14 pin op-amp RC3403ADB
The board is thick cream coloured, almost looks like "perf" and the traces are all solid "solder" traces, like a vintage Phase 90 board !!
I would suggest the NE5532 or a Ti- RC4559p for a nice "quality" op-amp but for "original" tone maybe the JRC4558D  would be best ?

Marty.

How similar (if at all) are the PCB layouts between the quad and dual opamp versions???

[analogmike]

How similar (if at all) are the PCB layouts between the quad and dual opamp versions???

Those versions of the OD-1 are quite similar except as I mentioned above the quad opamp and dual opamp traces need to be shuffled, and a few other traces for the bias resistors are different. I used 4 jumpers on the chip to make the 14 pin opamp work.

[G Kresge]

Damn it! I wish I could make a PCB from the schematic and just build one myself. I'm sitting here staring at it trying to draw it out, but I haven't got any idea what the hell I'm doing.

[MartyMart]

Damn it! I wish I could make a PCB from the schematic and just build one myself. I'm sitting here staring at it trying to draw it out, but I haven't got any idea what the hell I'm doing.

If you can borrow a vintage OD1, the "raised" solder traces should be easy to "trace" onto grease proof paper,( like we did as kids ) then stick a coresponding piece on top and "copy" in the components, from the top side.
You could then "tack" those onto a nice exact size piece of perfboard !
What do you think, possible ?
Or have a PCB made from it.
I know it can be done also on a scanner, scan both sides and print to see through plastic sheets, which you can stick to each other  
Just an idea.

Marty.

[G Kresge]

Well, what I originally intended to do was very similar to that. Before a couple of days ago - and finding out about the quad opamp version of the OD1 - I had scanned and meticulously "traced" the OD1's PCB with that exact intention. If anyone out there that has the quad version could send me a scan of the PCB (top and bottom) I would be incredibly grateful.