Boss - OD-1 Overdrive  [schematic]

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thyx
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Post by thyx »

Cool...thanks again!

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blackbunny
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Post by blackbunny »

thyx wrote:Cool...thanks again!
No worries. And here's the revised schematic I said I'd post.
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OD-1B revised schematic
OD-1B revised schematic

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thyx
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Post by thyx »

Looks good! Only note I'd make is Q1 is often a GR rating. Not sure why this is.

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Post by blackbunny »

thyx wrote:Looks good! Only note I'd make is Q1 is often a GR rating. Not sure why this is.
The 2SK30A data sheet says there are 4 grades of IDSS classification -
R(Red): 0.30~0.75, O(Orange): 0.60~1.40, Y(Yellow): 1.20~3.00, GR(Green): 2.60~6.50

Idss is the maximum drain current observed when the gate voltage is zero with respect to the source.

I think that means the GR FET allows more current to pass when turned off (pinched off) than the Y FET.
If that was the case, the Y would be better for the overdriven signal path as there would be less signal leaking through.

I guess the GR's would be cheaper in bulk buys, being less desirable for switching?
I'm not sure though. It may be the other way around!

Anyhow, both my OD-1B's have GR for Q1 and Y for Q2, and my OD-1A has 2SK30A Y FETs for both. Hmmm.

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Post by stratman007 »

hi there, I would like to say that this information has been very helpful. I just finished working on a Boss OD1 clone... ha-ha... i built it on perfboard and its up and running. How ever. I built the Quad version how ever since the Original RC3403 Ic is very rare and sometimes going for up to 25 bucks a single one on ebay. I built it with 2 dual op amps. 1 hi-fidelity for the buffers and 1 rd4558d for the Overdrive circuit. It worked perfectly fine, socketed everything and its up and running. I used this schematic.
https://www.diystompboxes.com/smfforum/ ... ic=62712.0

how ever I am looking for other quad Schematics to compare. I am a bit skeptical about the 10k ohm at the input of the 1st Overdrive opamp, since most other circuits for boss overdrive pedals calls for 100k. If you guys could shed some light I would greatly appreciate it :D

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Post by blackbunny »

stratman007 wrote:how ever I am looking for other quad Schematics to compare. I am a bit skeptical about the 10k ohm at the input of the 1st Overdrive opamp, since most other circuits for boss overdrive pedals calls for 100k. If you guys could shed some light I would greatly appreciate it
I just checked the pcb's of both my RC3403 quad op amp Boss OD-1 pedals. R4 is 10k in both of them, and it goes from pin 5 to ground as shown on the schematic.

The later transistor buffer models have 100k in that position, but the series coupling capacitor is reduced by a factor of 10 to .0047. The HP filter will therefore have a similar roll-off frequency.

I would guess that the later models' discrete transistor buffer can't drive the .047 / 10k load very well, whereas the RC3403 buffer can drive it easily. Most modern op amps will drive a 10k load easily, so whichever dual op amps you used should be fine.

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Post by stratman007 »

Thanks for clarifying that, I appreciate it. Today when I was A/B testing my Boss SD1 w/"Keeley Mod" with my OD-1 clone. I happened to come to the conclusion that the OD1 sounded more Midrange-y, and solid defined Highs the Gain is just Perfect, In the other hand the Level output was much less on the OD-1 than the SD1. My keeley SD1/ sounded more full, with more lows. Both sound great, and I love the difference since that is what I was going for, a different overdrive . Since I don't have an original OD1 to compare, I would appreciate it if you could A/B your OD-1 with an SD1 I would like to know if you notice the same as I did with my clone.

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Post by blackbunny »

stratman007 wrote:Today when I was A/B testing my Boss SD1 w/"Keeley Mod" with my OD-1 clone. I happened to come to the conclusion that the OD1 sounded more Midrange-y, and solid defined Highs the Gain is just Perfect, In the other hand the Level output was much less on the OD-1 than the SD1. My keeley SD1/ sounded more full, with more lows.
stratman007 wrote:Since I don't have an original OD1 to compare, I would appreciate it if you could A/B your OD-1 with an SD1 I would like to know if you notice the same as I did with my clone.
Are you referring to the SD-1 "Keeley Brown Mod" in which he changes various capacitors to stacked metal film and mica types, and increases the values of a couple of capacitors near the input for more low end? (There's another one where he inserts a BJT transistor in the feedback loop for a "vintage sound").

I have compared my OD-1 A & B quad op amp pedals to various stock and tweaked SD-1's; the OD-1 is definitely a midrange specialist. My OD-1's are brighter and tighter than even a stock SD-1. They really nail those Highway to Hell and Back in Black AC/DC tones, and can do brilliant Pete Townsend / HiWatt imitations.

Of course, if you plug them into a clean Fender Twin they sound super-aggressive with lots of bite, whereas they sound fatter and richer through a warm amp such as a Marshall JCM800 or Vintage Modern and a quad box.

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Post by stratman007 »

many thanks :D

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Post by atreidesheir »

If I was to build one of these, is a tl074 or tl064 going to work for the quad opamp.
IF yes, which on would be the best?

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Post by roseblood11 »

It will work, but i t might sound a bit different...
The 3403 isn't really rare: http://uk-electronic.de/onlineshop/prod ... a2b911e159
(I'll use the Reticon 4136, because I have lots of them, I guess there won't be a noticeable difference)
Watch the pinouts, not all quad opamps follow the tl0x4 standard...

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Post by atreidesheir »

cheaper than I thought. thanks
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Post by sinner »

Here's the 052-281B replica PCB I did while ago. No component layout yet, most of the job is done, just flip-flop circuity left to do. I'm involved into to many projects at ones to finish it up right now. It's better than nothing, and you can do the replacement PCB with it as is

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Post by blackbunny »

roseblood11 wrote:It will work, but i t might sound a bit different...
The 3403 isn't really rare: http://uk-electronic.de/onlineshop/prod ... a2b911e159
(I'll use the Reticon 4136, because I have lots of them, I guess there won't be a noticeable difference)
Watch the pinouts, not all quad opamps follow the tl0x4 standard...
Note that the MC3403 is not the same as the RC3403 IC Boss used in early OD-1s. The MC3403 is similar to an MC1741 quad op amp and sounds good in an OD-1 replica,
but the original Raytheon RC3403 is an unusual op amp with ground sensing inputs, and sounds noticeably different in this circuit compared to MC3403. Better or worse is personal taste.

I have 3 OD-1's with RC3403 chips, and have owned about 20 others including clones with 4558, LM833, LM324, TL074 and LF347 op amps.
Each type of op amp can sound good in this circuit, but none sound like the Raytheon RC3403 ones, which I have kept...and sold the others. Hope this helps!

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Post by roseblood11 »

blackbunny wrote:
roseblood11 wrote:but the original Raytheon RC3403 is an unusual op amp with ground sensing inputs,
Would does "ground sensing" mean here? Could anybody explain that and how it influences the sound in the OD-1?

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Post by blackbunny »

roseblood11 wrote:Would does "ground sensing" mean here? Could anybody explain that and how it influences the sound in the OD-1?
Good question! I read the data sheet for the RC3403A and it's not explained very clearly.
Compared to MC3403, the RC3403 seems to have higher slew rate, 1.2V / uS compared to 0.6v / uS, and the MC3403 doesn't seem to need a bias supply for single supply operation.

I don't know if this means one IC is better than the other, but it does make them sound different in this audio circuit. The OD-1 with an RC3403A / RC3403AD / RC3403ADB sounds a tad brighter than
the same circuit with an MC3403, and is a little tighter in the low frequencies, most noticeable when the Overdrive (gain) knob is cranked when playing a guitar with humbuckers.

The MC3403 actually sounded a little warmer with strat or tele type pickups. Using a 14 pin socket and the OD-1A / OD-1B layout, you can try different op amps.
RC3403, MC3403, KA3403, TL064/74/84, TLC2274 and LF347 will all work in this circuit. RC4136 has different pinout as you say, and is not interchangeable.,
Attachments
MC3403 description.pdf
(43.59 KiB) Downloaded 195 times
Raytheon RC3403A Quad Op Amp.pdf
(32.8 KiB) Downloaded 217 times

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Post by gotheriff »

CAN U HELP ME ON THIS ...........PLEASE ...

hello everyone I'm ... I'm a total novice and new to this forum my limit to electronics is very basic the best i could achieve is testing caps & soldering . i have a treasured boss od 1 with the raytheon chip it was working fine while playing my guitar ..and then one day my amp went a bit weird made a sort of deep humm so i switched everything inc the peda loff left it a while thinking it may have overheated i switched everything back on the amp was ok but the pedal woulnt work .. it had a hisssing noise when overdrive on but no guitar sound ! and no guitar sound in bypass hence the problem ...... so i thought ill have a look in my very limit knowledge i used a multimeter to test some conponants by accident as i tested the printed circuit board the pedal came to life for a split second .. then back as before ... but i don't really know what I'm doing so i thought i will ask the experts on here see if they can guild me on this !! problem .

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Post by gotheriff »

SEE PIC

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Post by MWichni »

Probably bad solder joint could be the problem. If only you can post some larger picture of the board (traces side and component side). Check the wires inside too, one could be broken.

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Mariusz.

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Post by gotheriff »

pics of internals

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