OD-3 vs SD-1

[solarplexus]

Hey there...

I have both the OD-3 and the SD-1.  I love both for different reasons.  First, the OD-3 has a LOT of headroom wich makes it a great booster and/or louder pedal for solos when coupled with a Ibanez Fat Cat.  What I don't like though is that after some mods (but I'm not done yet) it's kind of too mid-range for me (for now).  I love the SD-1 simply because of the sound I get after I do my own mods on it.  What I don't like is the bleedthrough that makes me feel like I'm dirtying up my signal even if I don't notice the bleedthrough (it's kind of psychological I guess).  Now here's my couple of questions for you experts:

1.  Is there a bleedthrough problem with the OD-3 as found in the SD-1

2.  Is there some mods I can do to the OD-3 so it can sound similar to the SD-1?

3.  Judging from Aron's "simple mods" page, you can increase the headroom of a pedal by removing one of the clipping diode in the circuit, at the cost of  some of the distortion (which I wouldn't mind on the SD-1)... Would that work on the SD-1 and which diode would you suggest be removed ?


I think that's all for now, you help will be very much appreciated!!

Matt

Ho! And please, stop by my band's website (www.meorion.com).

[solarplexus]

anyone ? 

[Phorhas]

2.  Is there some mods I can do to the OD-3 so it can sound similar to the SD-1?

Well, thses two are quite differant from each other, not only in tone but also in circuit topology. what you can do is do strengthen the signal going into the OA and also increase the gain of the OA.

Remove the 1uf Cap (C32 I belive) and replace the 3k3 resistor (R38) with a bigger value (I'd start with 10k)

Also try messing around with C24 - that's the capacitor going between the clipping diodes and drain of the FET gain stage.


These are mere suggestions by pondering over the schematic. I haven't tried thses my self. Tell us how it goes.

Have Fun

[wampcat1]

Please post the links to the schems in this thread so we can help better.
Thanks,
Brian

[solarplexus]

here's the OD-3 :

http://www.freeinfosociety.com/electronics/schemview.php?id=2299

and here's the SD-1:

http://www.freeinfosociety.com/electronics/schemview.php?id=169


Brian, I also changed the C7 cap with a 103K (on the OD-3), as suggested in you DIY sheets (which I love).  I like the sound I get, but the highs are a shrilling like a BD-2.  I tried changing the tone pot cap to a 683K (higher value than the original), but without much results to highs.  I also changed R38 with a 10k, put 2 1N4001 in series in D11 and D10, thinking it would increase the amount of distortion, which I think it did but I think it may be my imagination.  It's starting to sound very similar to a SD-1, but the SD-1 has better highs, more clarity and overall presence (after doing the mods I do, of course).  Is there something else I could do to improve that on the OD-3?  The headroom is, with the 2 diodes in series, still alot better than the SD-1, which is at 3 o'clock to equal 12 o'clock on the OD-3.

[WGTP]

The OD-3 is intriqueing design.  There appears to be 3 sets of clipping diodes and lots of tone shaping.  You may have to change the diodes in more than one stage to hear an effect.  C16 appears to be rolling off some hi's, so you try increasing it to reduce them further.

[solarplexus]

And what would be an ideal value for the tone pot cap (C17)?  Does changing all the clipping diodes to 1n4001s would improve the clarity or the overall distortion?  (when I mod pedals I always end up using the 1n4001s cause the sound is exactly what I like, well, usually)

[WGTP]

With multiple clipping stages, changing the diodes in one stage may drive successive stages more or less.  I can't predict what will happen, you may just have to try it.  It will be difficult to both reduce the amount of mid-range and cut the hi's.  It's a complex design. 

[wampcat1]

here's the OD-3 :

http://www.freeinfosociety.com/electronics/schemview.php?id=2299

and here's the SD-1:

http://www.freeinfosociety.com/electronics/schemview.php?id=169


Brian, I also changed the C7 cap with a 103K (on the OD-3), as suggested in you DIY sheets (which I love).  I like the sound I get, but the highs are a shrilling like a BD-2.  I tried changing the tone pot cap to a 683K (higher value than the original), but without much results to highs.  I also changed R38 with a 10k, put 2 1N4001 in series in D11 and D10, thinking it would increase the amount of distortion, which I think it did but I think it may be my imagination.  It's starting to sound very similar to a SD-1, but the SD-1 has better highs, more clarity and overall presence (after doing the mods I do, of course).  Is there something else I could do to improve that on the OD-3?  The headroom is, with the 2 diodes in series, still alot better than the SD-1, which is at 3 o'clock to equal 12 o'clock on the OD-3.

Here's what I would try, one change at a time to get rid of highs (values in uf):
c12: raise value... .0047/.0068/.01/.022/etc.
c16: raise value... .022/.033/.047/etc.
c17: raise value... .047/.068/.1/.15/etc.

I would experiment with C33 values as well -- you can tame the mids a bit there.

Hope that helps!

Thanks,
Brian

[wampcat1]

For more distortion on the od-3, try these:
increase r38 (experiment, try 10k/22k/47k/etc)
increase r50 (experiment, try 1k/2.2k/4.7k/etc)
increase r55 (try 1k)
jumper r54
increase c35 to 47uf

**these are all speculations! I haven't tried these, but looking at the schem they may/may not work! Do one change at a time. If you like it, keep it. If you don't, change it back to the stock part.

Hope that helps! Report back with your results!

Brian

[solarplexus]

Thanks Brian!!

And for the bleedthrough on the SD-1... is there that kind of problem with the OD-3?

[WGTP]

Of course, the r51 and c33 are the same funtionally as the RC network coming off the feedback loop in the SD-1.

Lowering r51 will increase the gain and roll off some bass, raising it will add bass and lower gain

Lowering c33 will decrease the gain and roll off some bass, raising it will add bass and gain. 

Try halving or doubling. 

I need to get one of those.   

[wampcat1]

Thanks Brian!!

And for the bleedthrough on the SD-1... is there that kind of problem with the OD-3?

I haven't experienced that on the od-3...not to say that it isn't there or that the potential of it isn't there (especially after changing the gain structure), but if there is a little bit of bleedthrough it isn't nearly as noticeable as the sd-1.

Thanks,
Brian

[solarplexus]

Ok I'm done...

Here are the overall mods I did:


C7 > 0.0047 uF  (472K)
C16 > 0.022 uF  (223K)
C17 > 0.068 uF  (683K)
C28 > 0.22 uF  (224K)
C32 > remove (no jumper)
C33 > 1 uF  (105K)
R38 > 8K2
R42 > 1K0
R54 > Jumper
R55 > 1K0
D10 > 2x1N4001 in series
D11 > 2x1N4001 in series

I would put a soundclip but my microphones are at our jam room.  The pedal has what I like about the SD-1: Clarity and mid hump, but without the shrilling highs (although it is a little on the high-end, but not as much as the SD-1).  The pedal has just enough bass (felt there was too much in the beginning) and equal gain compared to the SD-1.  Will definitely cut through in a mix better than a SD-1 and still has way more headroom than the SD-1.  I couldn't test it as a booster because my tube amp is also at the jam room (I tested it on a solid state amp, Crate GX-80 RMS, Celestion Silver Series), but compared to what I used before (the BSIABII), this one will be better: more controllable tone pot, more output and definitely less noise than the BSIABII.  And in my opinion, used as an overdrive box, it sound BETTER than the BSIABII (yes... I said it) and better than the SD-1... and the rest of the boxes I have here.

Thanks to everyone that helped, I finally got the tone I wanted out of that pedal.

One thing though... After making these changes, could it have caused a bleedthrough problem?  Although I don't hear anything at low volume, I am wondering if it could happen that there would be a bleedthrough tainting my tone and where could it be?

Anyways,

Thanks to you all,

Matt

[wampcat1]

Ok I'm done...

Here are the overall mods I did:


C7 > 0.0047 uF  (472K)
C16 > 0.022 uF  (223K)
C17 > 0.068 uF  (683K)
C28 > 0.22 uF  (224K)
C32 > remove (no jumper)
C33 > 1 uF  (105K)
R38 > 8K2
R42 > 1K0
R54 > Jumper
R55 > 1K0
D10 > 2x1N4001 in series
D11 > 2x1N4001 in series

I would put a soundclip but my microphones are at our jam room.  The pedal has what I like about the SD-1: Clarity and mid hump, but without the shrilling highs (although it is a little on the high-end, but not as much as the SD-1).  The pedal has just enough bass (felt there was too much in the beginning) and equal gain compared to the SD-1.  Will definitely cut through in a mix better than a SD-1 and still has way more headroom than the SD-1.  I couldn't test it as a booster because my tube amp is also at the jam room (I tested it on a solid state amp, Crate GX-80 RMS, Celestion Silver Series), but compared to what I used before (the BSIABII), this one will be better: more controllable tone pot, more output and definitely less noise than the BSIABII.  And in my opinion, used as an overdrive box, it sound BETTER than the BSIABII (yes... I said it) and better than the SD-1... and the rest of the boxes I have here.

Thanks to everyone that helped, I finally got the tone I wanted out of that pedal.

One thing though... After making these changes, could it have caused a bleedthrough problem?  Although I don't hear anything at low volume, I am wondering if it could happen that there would be a bleedthrough tainting my tone and where could it be?

Anyways,

Thanks to you all,

Matt

Awesome!! Do you mind if I post it on the IG forum?

Thanks,
Brian

[WGTP]

Cool.   The placement of D9 and D12 seems odd to me.  It appears to be prior to a gain stage and after a notch filter that reduces level, so I can't see them having much effect.  Does the schmatic seem to be correct in that area?  What effect did removing C32 have?

I added the mods in blue to the schematic, if you like I can email it to you.

[Phorhas]

I have pondered that myself some time ago.

Just a thought... maybe they wanted it to be able to work good with an outside boost.

There's not mush to clip there, and these don't seem like protection diodes... hmm... could the BOSS guys actually designed the Od-3 with that in mind?


... probably not ...

[WGTP]

Interesting thought.  They talk about cascading pedals, so maybe that is it.  It would add an additional clipping stage that didn't do much by it'self.  GE's there make more since, from what little I understand about it.   

[solarplexus]

Hey Brian,

you can use the mod in the IG forum, I don't mind at all. 

WTGP :  Removing C32 removed a lot of bass and boosted a lot of mids and highs.  Although it was too much, tampering with C7 would help with the bass response, lowering it too much would do the same thing as C32 though, you have to make small changes.  For example, I started with a 0.001 uF, and there was too much mids and highs, not enough bass.  After I switch to a 0.01 uF and there was too much bass and the mids and highs were not apparant enough.  Then I changed it to a 0.0047, everything was well balanced with the change I made in C32 and with the other capacitors.  Keep in mind that C7 was the last change I made.

[WGTP]

Keep in mind that mind I don't know much about this stuff, but as the schematic is drawn I don't see how there would be enough signal at D9 and D12 to reach their clipping threshold off around .7v.  This would make c32 pointless.  If there is some gain somewhere before those diodes then what your saying makes sence.  A cap to ground like that has the effect of clipping the hi's but allowing the low's to go thru unclipped.  I wonder if Q8 or Q10 isn't a gain stage???