DOD 250 Overdrive question!

[stand]

Hi!
I have question about DOD 250 Overdrive, so I hope someone can help here...

Though I am not quite a beginner in this world of soldering I must admit that it will be the first guitar effect I ever made. I am mainly keyboard player and as you already know you don't have to worry about pedals if you play keys nowadays. Anyway, my kid plays guitar and since we cannot afford one of those fancy & shiny multi-effect boxes I decided to help him by using some interesting diagram from the net. Since we both like Y.Malmsteen we decided to go for DOD 250/308 overdrive clone which uses 741, 4558 or similar IC. So, we found some excellent articles which cover this topic/pedal. I already figured out the main facts about it, but... Finally, here is my basic question – on some sites I have noticed conclusion that this pedal could be used just to amplify or tight up your signal, not to made real squeaking or growling fuzz/distortion. On the other hand, I saw that I should play a little with these clipping diodes to get the sound I want... Now I don't know what to think, and what to do... Is it good "first pedal project" which will help us to get good "kill the neighbor"sound, or I just should forget about it and go for some "Fuzz Face" clone? I must admit that at this level I am not ready to make any very demanding distortion pedal, so I'll stay with simple things for now.

Thanks in advance for all suggestions and advices!!!

Dejan

[burnt fingers]

I think this would be a great first project.  I would say just solder it up as the schematic and layouts you have say.  The 1n4148 diodes work well.  I just made one of these for a buddy of mine.  I a/b'd it with an early 80's yellow 250 that I already owned and they sounded nearly identical.  The 741 is a good op amp.  It's a little hissy at super high gain but it sounds fine.  This pedal will go from mild overdrive to some pretty good distortion.  I used my little yellow box for years and I played Motly crue, ozzy, kiss type stuff.  I don't think you will be dissapoited with this box.

Scott

[petemoore]

  Is the YJM the rather trebly one? IIRC The main difference/reason is mainly the staging cap values.
  The 741 type OA Clippers work great, your amp might like a different voicing, consider socketing a cap or two as well as the OA, so that the circuit can be tuned to your version of 'optimal' with your amp/guitar?

[stand]

To "burnt fingers":
Thank you so much, pall!!! I worried if I could get just louder guitar sound (but still quite clean), which really then would be waste of time and money. After your short explanation I'll certainly go for DOD's YJM 308 clone though I do believe that some tweaking here or there would even make it closer to our taste (from Toto, YJM, Dream T. to blues). Here is another question (sorry!): our amp doesn't have effect loop so all pedals that we just tried were used by simple connection guitar -> pedal -> amp. I've heard that Y. Malmsteen uses eff. loop on his amp to get his famous "signature tone". Do you think it will work fine with our simple approach?
To "petemoore":  first thing must go first – I must apologize because my "DIY" English is probably not at some very high level, especially if we talk about electronics. So, maybe I couldn't understand your words quite well. Is "staging cap" is actually an input cap (I hope that you have DOD 250 diagram somewhere in your pockets)? If so, I bet YJM's version will be "trebly" – on DOD 250 original scheme there is 10nF cap, but Yngwie suggested 10 times lower value (just 1nF) so it is probably the reason, isn't it? Somewhere I found advice that says – clipping diodes will control amount of "fuzziness" where Ge – Si – Leds diodes will make more distorted to cleaner sound (respectively). I want to put sockets for input cap, IC and diodes, and to play with different combinations of values. Here is a question for you – do you think 4558 (MC4558CN at my supplier) will be less noisy than 741 but still 'rough' enough for this pedal? Should I send DOD 308/250 diagram to you?

Thanks again for your advices!

Dejan

[Mark Hammer]

The simplest thing is to change the value of the .047uf cap that is in series with the gain control.  The way this and several similar pedals work is that as the gain is increased, the setting of the control interacts with that capacitor to cut out more and more bass.  At minimum gain, the low end is rolled off starting around 6hz, which you obviously won't notice.  With the control set to half its resistance, this moves up to about 13hz (still no great hardship).  Turning the gain up (and the pot down to about 1/10 its maximum value), it rolls off bass around 195hz, which is now going to start to make a difference in the meatiness or heft of the tone.  At maximum gain, the low end is rolled off (albeit gradually) starting around 720hz.

In one respect, this is clever because it produces a buzzier, reedier sound as fuzz is increased.  So, it is kind of a two-for-the-price of-one control.  At the same time, many players want to add the fuzz but keep the bottom, and this obligatory loss of bass drives them nuts.

So, back to the cap change.  If you change that capacitor for a unit with a .22uf value, then at maximum gain, the rolloff will start around 154hz, which is probably something you can live with.  If you want, you can use a toggle switch to select between twop capacitors for stock tone vs keep-the-bass.  If your tone is still too buzzy and fizzy, then consider using a .0022uf capacitor in parallel with the clipping diodes, instead of the .001uf unit in the original.

[lovric]

Dejane,

try LM833 or NE5532 or TL2272, they should keep the noise down a bit. the noise is really noticeable at high gain. other than that, see what mark says.

marin

[stand]

It seems that there are 5 places on this project where I should put sockets to be able to play with different values (input cap, 0.047uF cap, IC, clipping diodes and cap in parallel with diodes). Man, thank you for such a detailed and logical explanation. Of course, most of us don't want to end up with buzzy "mosquito-like" sound when we add more and more fuzz. If this is what would happen if I use 0.047uF cap I'll probably try it with some other (higher) value.
I already tried many Boss/Ibanez fuzz/distortion pedals in my life, and I figured out that it's very hard task to obtain good solo (squeakin') sound and fat impressive sound for chords backing, so I know that you cannot expect to get everything from just one simple pedal. There is probably isn't any "ultimate distortion pedal", so with this DIY project I am trying just to get decent sound from our guitar. But, I think that there is still enough room to change some parts and to achieve good results. Btw, what would be better solution – 741 or 4558 IC? I've heard that 741 is very noisy, what about 4558?
Anyway, thank you for your advices, I'll keep your words in my mind and try to see what cap value sounds most suitable.
Finally, please sorry if my English is not very good – I never had chance to learn it at school, so...

Dejan S

p.s. Marin, thanks for your advice. I'll check out some of those ICs, it would be fine to find some less noisy thing. Mada "buka" ponekad  ne smeta, ha, ha  . Pozdrav!!!

[Mark Hammer]

Your English is just fine.

The .047uf capacitor I mentioned will most definitely be the one having the most effect on bass.

To add to your education, consider this...

When an op-amp is used the way it is in the DOD250, there are two ways you can increase the gain.  One is to increase the resistance between the output and the '-' pin, and the other way is to decrease the resistance between the '-' pin and ground.  How are they different?  Well when a resistor is used in the "feedback loop" (between output and '-'), if there is a capacitor in parallel with it, the treble is decreased as the resistor gets bigger.  This is the approach used in the Tube Screamer.  It's a pretty good idea, since as the gain is increased, any noise coming with the guitar is more annoying, so cutting the treble more helps.  If it is a distortion pedal, rolling off some treble as the distortion is increased also helps to make the distortion less "fizzy".

Other times, people do not want to change the treble, so they use the resistor between '-' and ground.  Here, the *bass* rolloff depends on the value of the resistor and the capacitor in series with it.  As the resistor gets smaller, the gain is increased but the bass rolloff also goes up higher and higher. 

If the capacitorin the feedback loop is kept small enough, then increasing that resistor will not result in any noticeable change in treble.  If the cap gets bigger, the treble may be significantly reduced.  Sometimes thatcan be an advantage, and sometimes not.  If the capacitor in the ground leg is large/high enough, then the bass rolloff won't change in any noticeable way as you increase the gain with that resistance.  Of course, if the cap is a smaller/lower value, then changes to gain can change the bass end a lot.

One compromise that is done sometimes is to adjust BOTH resistances at the same time.  Here, the "wiper" (the middle moveable contact) of the pot goes to the '-' pin and whatever is on one side of the wiper is part of the feedback resistance, while whatever is on the other side of the wiper is part of the ground leg resistance.  Making either one of the two sides higher/bigger results in the other one getting smaller.  Changing both resistances at the same time can produce large changes in gain (by making one resistance bigger as it makes the other smaller) without having to change the low-end rolloff or the high-end rolloff too much.

[vanhansen]

Socket the output cap as well.  The stock value might be fine but still fun to play with.

The 741 and 4558 are not interchangeable.  The 741 is a single op-amp, the 4558 is a dual op-amp.  Different pinouts.

[stand]

To Mark:
From your words I realized that you're diving so deep in these waters... At the same time I'm just trying to keep swimmin', if you know what I mean. Your explanations were again so direct and made me blush because I had no idea about these (probably basic) facts. I know, it was not your intention; such sites/forums are here to help us to exchange ideas and to learn/teach. Anyway, thanks again for your advices, I could spend ages to get it all by reading books, making mistakes, burning our garage, etc.
So, to avoid too many words, I must ask you to tell me what you suggest about this project. As I wrote in previous post, I'd like to get lots of fuzz, but at the same time I'd be happy to keep "fat" (or hefty) sound as much as possible. How could I implant there your idea about using pot as unique way to adjust both feedback and ground leg resistances? Do you think I should just make this effect as diagram says (with few sockets that will give me possibility to change values of caps, diodes, ICs) or you suggest to go for addition of such "magic" pot (and maybe for different values of other resistors/caps) to get a system with so many changeable parameters. Though it really sounds like a tempting bite, it probably wouldn't be a "piece of cake" for me. With so many things to adjust I could get lost in tweaking. Of course, maybe I am wrong and maybe I just misunderstood your words. If you want you can send your (or any other appropriate) e-mail address to my address (largecornel@yahoo.com). This way I'd be able to send to you diagram of this pedal (DOD YJM 308) that I made. Then you can write/draw what you think about it and about possible tweaks and changes. If you don't have time for it I won't be disappointed at all – I'll be happy to "stay in tune" with this little "tweakers-community" and to get advices at forum.

To vanhansen:
Are you talking about cap that is connected to IC output? If so, then I must admit that it would be really a challenge to change all these values and to keep ears in good working order. Anyway, that's why we are all here, aren't we... Thanks for your advice! And, thanks for your warning about 741/4558 incompatibility – I already decided to go for less noisy ICs, so I'll probably buy 4558, NE5532 and TLC272. All of them should be dual op-amps, so I could use the same IC socket to play with it. I hope that it is not bad choice, anyway. Is there any other appropriate low-noise ICs?

[pi22seven]

The 1458 is supposed to be a dual op amp version of the 741 and has the same pinout as the 4558 so you could play around with that.

I'm probably going to be changing out the 4558 in my OD 250 with a 1458 pretty soon.

[petemoore]

So, to avoid too many words, I must ask you to tell me what you suggest about this project. As I wrote in previous post, I'd like to get lots of fuzz, but at the same time I'd be happy to keep "fat" (or hefty) sound as much as possible.
  Breadboard...
  I just perf up a socketted where I want it board...that'd be ME tho...parts aren't guaranteed tight unless...OT...Long Story...too long considering the parts at RS for a DIST+ Type thing are 10 bux or so...
  THe DIST+ Is quite similar, but voiced more 'normal', might be worth a look at the schematic.
  If the input cap is marked as 1n, put a socket there or see if there's enough bass in the circuit with the 1n. All caps oriented in signal path like this will have similar effect of rolling off bass as the values are made smaller.
  The gainpot cap Mark Mentioned ...
  If you're perfing it...socketting the input at least and gaincap might be a good idea, the opamps should always get sockets, they burn too easy, not really worth trying to soldering on 'em, the dioes and cap across them can all be put on a 6pin or 8 pin IC socket also, just rail one side for Gnd. and rail the other side for the top of diodes/signal path, with some solid core wire.
  I have a special techniques [that are 'funky'] for leads to stay stuk in sockets, but some people use hot melt glue...having lots of EXPerience, the OA's never fall out, diodes and teeny cap hardly ever [if they're trimmed, bent and installed 'just right], it's the electrolytic that still probably won't fall out where you could use hotmelt glue, I've had decent luck with the 'gum stickystuff' [name?..office supply].
  Also you may want to see AMZ's lab notebook for some different control ideas..'Warp Control'...
  Fuzzcentrals "Liquid Drive' uses 'higher spec' Opamp.
  I find the LM741 not very noisy at all, and the DIST+ type things I have seem dependant on it's 'shortcomings' for optimal Distortion tone...of course...YMMV/IMO...

[stand]

To pi22seven:
I tried to investigate about this pedal, and most of DIY-ers described 741 as very noisy IC. I never used it so I cannot judge about it; I just believed that it is noisy because so many people say so. On the other hand, petemoore claims that it isn't very noisy at all. Of course, since IC 1458 is not expensive (25 cents) I'll include it in testing process (4 ICs are candidates at this moment!). Thanks for your info about 1458. I hope that you'll share with all of us your own experience about 4558 and OD 250.

To petemoore:
Thanks for your advices about "socketing".  I supposed it would be boring and risky job to test ICs by soldering-desoldering, and I even decided to leave IC socket there after I decide which one is most appropriate. This way I'll be able to try even some other ICs in the future. I hope that such idea doesn't sound stupid to you... 
I know you'll think that I am dumb or something, but I really couldn't understand few words you mentioned in your post (perf/perfing, OT, YMMV/IMO), even my dictionary couldn't help here. I figured out what's OA, though... Like I said, English isn't my mother-language so we don't use  such abbreviations here (which is not your problem, of course). In any case, I'd feel better if you were closer – then you could show to me your special tricks for leads and sockets.
I'll certainly change gain pot cap to see what I can get there. And, thanks for your advice to check out AMZ's "Warp Control", "Liquid Drive", etc. All new infos are welcome...
I've noticed that DIST+ is very similar to this project. I decided to go for YJM 308 just because I liked OD250 diagram and Malmsteens sound. I'll try to find some DIST+ sound clips on the net to hear how it sounds. Who knows, maybe I'll end up with something between DIST+ and OD250, who knows.
About 'noisy' 741 – see above...
Once more, thank you for another set of valuable advices. I'll let you know what I did as soon as I get all parts, set them all and test this pedal.

Dejan

[Mark Hammer]

I must ask you to tell me what you suggest about this project. As I wrote in previous post, I'd like to get lots of fuzz, but at the same time I'd be happy to keep "fat" (or hefty) sound as much as possible. How could I implant there your idea about using pot as unique way to adjust both feedback and ground leg resistances? Do you think I should just make this effect as diagram says (with few sockets that will give me possibility to change values of caps, diodes, ICs) or you suggest to go for addition of such "magic" pot (and maybe for different values of other resistors/caps) to get a system with so many changeable parameters. Though it really sounds like a tempting bite, it probably wouldn't be a "piece of cake" for me. With so many things to adjust I could get lost in tweaking.

I salute your willingness to learn!   For now, the fastest route to get the sound you want is to simply make that capacitor I mentioned larger in value.  No need to start playing with where the pot goes...until you are tired of playing the guitar and find more pleasure in the pedal than in the playing.

I don't want to complicate anything but here we reach a choice-point that might make a difference for you.

Whenever a capacitor is unable to release the charge it has stored up, that stored charge will rush out at the first available opportunity.  In pedals, whenever a critical capacitor goes from being unconnected to connected, we often hear a pop, as that stored charge rushes out.  If the capacitor is at the input or the output of an effect, the easy solution is to provide a resistor that always connects the "free" end of the capacitor to ground.  But what about capacitors you want to switch, or switch between?

When people want to switch between a higher and a lower value capacitor, they often use a toggle-switch to connect the one cap or the other.  If the switching is done while the pedal or amplifier/speaker is off, the *source* of the pop will occur, but you won't get to hear it.  If you have your Les Paul plugged into your 100W amplifier with everything set to 11, and you reach down to flick that switch with everything on, the pop may be VERY unpleasant (and unprofessional). 

Can you eliminate it?  Yes, by using capacitors in series.  When placed in series, the value of two capacitors will always be less than the value of the lowest one, using the formula 1/C = 1/Ca + 1/Cb.  So, if you had one 0.1uf (100nf) capacitor in series with another .068uf (68nf) capacitor, their combination would be about 40.5nf (.0405uf).  If one of those two capacitors is "shunted" (i.e., a straight wire connection in parallel) then their "combination" is now equal to whichever remaining cap is not shunted.  If we shunt the 0.1uf one, then their series capacitance is now 68nf.  If we shunt the 68nf one, then the series capacitance is now 100nf.  But here is the important part: at no time was there ever a "free end" of either capacitor that could not discharge the stored current in the cap.

So, if you wanted to be able to select between the original capacitor value, and some change in capacitor value that would help you retain the bass, you would need to switch cap values.  The method described allows you to do it in a way that produces no audible pop.  Since you have a target of .047uf, you have the choice of either using combination that gets you .047 when two are used in series, or .047uf when one of a pair is shunted.  If two .1uf caps are placed in series, they will yield a capacitance .of .05uf.  Shunting either one of those two will bring you back up to .1uf again.  If you stick a .22uf cap in series with .068uf, you get a value of .052uf, .045uf if you use .056uf instead of .o68 for the smaller one.  Either way, if you shunt the smaller value, the capacitance now jumps up to .22uf.

This demonstrates how you can use two capacitors and a toggle switch to achieve different kinds of bass rolloffs as you increase the gain by decreasing the resistance of the ground leg...without the pop.

[lovric]

drugar ima dod yjm 308, i stvarno je dobar zvuk. 

250 or 308 are simple good first time projects. each one *will* kill the neighbourhood. what mark says are expert suggestions aimed at fine tuning it to your preference. although this effect is fine by default .

fuzzface schematic looks easy enough but building it may prove difficult due to finding appropriate transistors.

[vanhansen]

Mark, great info on the toggling of caps.  This means I have a pop problem on my Rangemaster and need to put a cap in there, but it would be parallel and I want to switch from the stock .0068uf cap to .01uf.  My DPDT has a .0068 on one side and a .01 on the other then two wires from the switch to where the cap would go.  So now I need to figure out what value to put back in the board (sockets are still there too  ).  Might need to switch the values on the switch too.

[Mark Hammer]

Thanks, Van.

There are plenty of people for whom the popping is a non-issue, either because they don't mind or because they are scrupulous about never having the volume up or effect engaged when they switch, or because they rarely use the switch.  In this sense, it is diferent than popping coming from bypass switching, since the desire to go back and forth from effect to no effect is something you do WHEN plugged in with the volume up.  The one situation (bypass popping) demands a solution, but the other one simply benefits from a solution, and if it doesn't bother you as is, fine.

As for where the bright idea for serial caps came from, tip your hat to John Hollis, not me.

[vanhansen]

Thanks, Van.

There are plenty of people for whom the popping is a non-issue, either because they don't mind or because they are scrupulous about never having the volume up or effect engaged when they switch, or because they rarely use the switch.  In this sense, it is diferent than popping coming from bypass switching, since the desire to go back and forth from effect to no effect is something you do WHEN plugged in with the volume up.  The one situation (bypass popping) demands a solution, but the other one simply benefits from a solution, and if it doesn't bother you as is, fine.

As for where the bright idea for serial caps came from, tip your hat to John Hollis, not me.

Ahh, I see.  Makes more sense.  On my home rig with the SS amp it's not really an issue.  It might be different when I plug it in to the big Marshall though.  Haven't done that since putting the switch in yet.  I'll wait and see how it behaves with it and then go from there.

Regardless of who to tip the hat too, it's still a great idea.  I'm seeing lots of stuff from John pop up lately or I'm just realizing that folks are passing along what he's already said.  Anyway, thanks for sharing that.

[stand]

To Mark:
Someone said that we are young as long as we want to learn...
I'll certainly try both 'factory' and a 0.22uF cap to see what sounds better to me and my kid. Also I'll see about output cap if sound is too buzzy. I probably won't fight against pops at this level - I'll just test it and tweak here and there. But, I've heard about popping problem from some guitar players, so your explanation how to solve it is really so valuable. I see, some people already appreciate it.

To Marin Lovric:
Znaci, imao sam srece pri selekciji projekta... Mada, priznajem - Yngwie je tu malo "pomogao" ... Pozdravi druga.

I don't want to kill my neighbors, they're all decent & nice people. Though they all have damaged hearing, I don't know why 

You're probably right about Fuzz Face – I decided to switch to IC based project because DIY-ers complained about problems to find/match appropriate Ge transistors. And I've heard some FF sound clips... I was not very happy with it, I must admit it. Of course, it's all about personal tastes...

To rest of the crew:

"Thanks!" goes to all of you, guys. Without you I'd still hesitate what to do...