Dod Od-250

[Boy Howdy]

I have an old (not reissue ... I think) yellow OD-250. These apparently sound inferior to the original gray OD-250. The gray used an LM741 chip and mine uses a TL081CP. I'm going to get a 741 at some point, but I'm curious what you guys think, am I likely hear any substantial difference?

I think what these things do best is when they are used as a booster (with a bit of hair). They give a fairly hefty level boost. But if the goal is to simulate tube amp distortion it fails. Sounds pretty bad. BUT, the gray 250 sample that tonefrenzy.com has sounds awesome.

So, am I likely to hear a difference between the two opamps?

[bulldogguitars]

I personally think you will hear a difference. I would install an 8 pin socket into the board where the IC is now and experiment with different ICs. That match that pin configuration of course. There are other mods you can do to it to really bring it to life.

[Boy Howdy]

Such as????

I'm all ears! (Not really. If I were, how would I type? I'd have no fingers.)

Edit: I know about changing the input cap. I fooled around with that at one point, I ended up leaving it as is. I didn't find the extra bass all that great sounding. It sounded fuller but flabbier too.

[bulldogguitars]

Let me go through my notes after work tomorrow and I will PM you with what I have and maybe have some more ideas. Danny

[petemoore]

Yupp...'klunky' 741, with it's 'weak' performance compared to more modern types like TL or 4558, does make a difference in the ground clipper circuits like 250, DIST+, New Clipper, a host of others I've build and modded.
diodes and that cap across them can change the distortion character by raising/lowering the clipping thresholds of the + and - signal swings, higher threshold = more output volume/softer clipping [more opamp sound], but I prefer Si's, either for symmetric clipping [back to back diodes] or assymetric clipping [one one way, two the other way], maybe an Si/Ge on the two diode side.

[Boy Howdy]

I'll be waiting...

to hear from you, Danny.

Hey Pete, I've been thinking about diodes a lot lately. How do the silicon sound vs. the germanium? Do the numbers on these things matter much? Can I just go grab some stuff at radio shack?

I changed the diodes in a Daddy-O once (replaced the red LEDs with germaniums - 3 on one side and 2 or 4 on the other (can't remember exactly). I liked it much better. Sounded really raucous with a higher distortion level and higher tone settings, and just really nice and musical at lower settings of tone and distortion level. I wish I'd kept that thing now.

[magna1]

dod 250's

Hello guy's, new member here, good to be on board! Just a quick back ground: Been playin/performing for some 30 ish years (man, gettin old!) bands out in L.A. in the mid late 70's, and now in Chicago land. Almost exclusively single coil guy (strats, teles) and have or have owned most every thing imaginable- read, blown way too much $$ searchin for the tone. Anyway have come full circle and for a number of years have gone to simple is good, 2 or 3 knob amps and 1 or 2 pedals thats it. Not that any of this gains me any credability, just that i think ive got an decent handle on tone and musical maturity.

Now, if i may comment on the 250's, ( i collect and have all versions ) they orignaly came with the 741 chip and occasionaly the 351n. I find they are different but very similar and hard to choose a winner. To the member who say's the 741 is clunky and weak compared the re-issue's 4558, i'd have to respectfuly strongly dis-agree, and say that perhaps you had a bad one. In every case or comparison ive made with an oldie (yellow or grey), the 741/351 is far more muscular in regard to output and firmness. Every re-issue ive tried is weak and farty in its output, NOT gain, but volume/ boost. In addition i find them horribly thin and harsh in the high end, ( tho even the oldies get brighter as you increase the gain towards max). If you compare the circuit and values of the components they are vastly different, considering they are still bone simple compared to the plethera of od's on the market. The defining sound of the original IS a slightly loose low end, as compared to todays mods and boutiques with their tight articulate response. While beauty is in the "ears" of the beholder, i just think mod-ing an original (circa late 70's early 80's) to sound like a sd-1 etc. with assymetrical/symetrical clipping etc. is missing the point of this UNDERATED pedal. If you find it too bright, or too loose, than its really just not the right pedal for your amp! and deviating from the original circuit will only yield a different and probably inferior pedal to something else thats already availible.

That being said, an important caveat: this pedal can and does sound horrible with certain amps. In my 65' vibrolux Rvb, you'd want to smash it with a hammer, while in say a Dr.Z Rt.66 or an old Magnatone 441 it IMHO is un-rivaled by ANY boutique ive tried. Also important: i'm talking live on stage performance, not in isolation in the basement or home studio. One thing experience has taught me, is that what sounds good in the basement rarely sounds good on-stage, and visa versa! Where most od's squish down under heavy picks/big strings, they stay firm, i like to call it muscular. The point being, i have not found a pedal that is all things to all amps and styles. I feel to my ears that this pedal (originals only) in the right amp, (critical) is also the most transparent, again, of any ive played. Of course "transparent" opens up a whole other can of worms doesnt it? Like describing "what your definition of clean is". A young metalers clean, or a county pickers clean, etc.

Sorry for the ramble/rant, feww!, and i hope i havent offended anyone with my "opinions". I'm just very passionate about this underated beaut of a pedal and feel that success lies in matching the right gear for the right player. We all have to go thru the process of discovering who you really are musically, and if your identity is strong enough, you'll sound like you no matter what diode or chip you have! And then,... the gear choices are a easy! Peace

[cjlectronics]

Magna1... your post should be published in a guitar effects user journal. I've been repairing and modding guitar effects as a business for over 15 years and you hit the nail on the head with not all effects work in all situations. Aside from the OD250 which I own an original yellow one with a 741 and its awesome, it does not work in all situations. What works in the club setting might not work in my tech room and might not work with another guitar pedal in my chain.

I live by the KIS (Keep it Simple) principle and this is how I approach many things first. Start simple and take the easy known path. Then expand on that if necessary but remember you can always fall back to what is known and proven.

OK...OD 250 note: I have modded many OD 250's and most of the requests are to replace the op amp with a socket and install a 741. All other passives are kept stock. This is a known good sound in many situations.

CJL

[Mark Hammer]

1) The 741 is generally a pretty crappy chip for audio purposes. Some pedals, like the Distortion+ and early 250 exploited it for its limitations. If you lift the clipping diodes out of circuit, the damn thing still distorts even at modest gain settings, albeit mildly. My sense is that this is a product of the rather unusual biasing used in the Distortion+ (when was the last time you saw Vref being supplied by a pair of 1M resistors?). Not sure what changes in biasing may have transpired in the 250 over successive issues. The last issues use a more conventional 22k+22k biasing divider. In any event, it is important to track the other design changes that occur with each issue/chip-change. My sense is that replacement of the op-amp guarantees very little unless the corresponding support circuitry is in place. For instance, a 741 will behave differently with 22k+22k+470k biasing than it would with 1M+1M+1M biasing.

2) The Dist+, YJM308 and 250 all use the ground leg resistance of a noninverting op-amp to set gain. As resistance gets smaller, gain goes up. Unfortunately, so does the low-end rolloff. In the Dist+, the 4k7 minimum resistance (at max gain) and .047uf cap yield a rolloff below 720hz, hence the rather shrill tone. While the resistors may be 5% tolerance, the caps can be 20%, leading to substantial pedal-to-pedal variance in both output levels and meatiness. If that weren't enough, there is diode-to-diode variation in voltage drop, leading to both different degrees of clipping and output level.

3) I've done some experiments using a single Distortion+, swapping op-amps, taking soundclips, and editing the clips together in a row. The op-amps CAN produce different nuances to the clipping, with some sounding raunchier than others. Trouble is that the variations in passive components from one pedal to another make a lot of the reputed chip-to-chip differences people profess to hear (and probably do hear) more likely to be the result of passive component differences than chip differences. At the very least, it is difficult to ascertain what portion of the audible differences comes from the chip vs the remainder of the circuit.

[Regis]

1) The 741 is generally a pretty crappy chip for audio purposes. Some pedals, like the Distortion+ and early 250 exploited it for its limitations. If you lift the clipping diodes out of circuit, the damn thing still distorts even at modest gain settings, albeit mildly. My sense is that this is a product of the rather unusual biasing used in the Distortion+ (when was the last time you saw Vref being supplied by a pair of 1M resistors?). Not sure what changes in biasing may have transpired in the 250 over successive issues. The last issues use a more conventional 22k+22k biasing divider. In any event, it is important to track the other design changes that occur with each issue/chip-change. My sense is that replacement of the op-amp guarantees very little unless the corresponding support circuitry is in place. For instance, a 741 will behave differently with 22k+22k+470k biasing than it would with 1M+1M+1M biasing.

2) The Dist+, YJM308 and 250 all use the ground leg resistance of a noninverting op-amp to set gain. As resistance gets smaller, gain goes up. Unfortunately, so does the low-end rolloff. In the Dist+, the 4k7 minimum resistance (at max gain) and .047uf cap yield a rolloff below 720hz, hence the rather shrill tone. While the resistors may be 5% tolerance, the caps can be 20%, leading to substantial pedal-to-pedal variance in both output levels and meatiness. If that weren't enough, there is diode-to-diode variation in voltage drop, leading to both different degrees of clipping and output level.

3) I've done some experiments using a single Distortion+, swapping op-amps, taking soundclips, and editing the clips together in a row. The op-amps CAN produce different nuances to the clipping, with some sounding raunchier than others. Trouble is that the variations in passive components from one pedal to another make a lot of the reputed chip-to-chip differences people profess to hear (and probably do hear) more likely to be the result of passive component differences than chip differences. At the very least, it is difficult to ascertain what portion of the audible differences comes from the chip vs the remainder of the circuit.

Hi Mark,

Not trying to hijack the thread, but I have a YJM308 and would like any suggestions regarding any mods to get it to sound like and old 250. I actually have a couple of old 741 in my junk box I could use if you think that would help. I realize the pinout is different.

Thanks,
Regis

[dumbassbob]

DOD Pedals

Its really funny how 25 years ago Noone would even think of useing a DOD.Everything was MXR, Boss. I remember buying a DOD OD,and the 280 compressor and a 360 EQ All my buds laughed at me for buy'n this Cheap junk.And Tube screamers forget it that trebley lo gain. guys were give'n em away.And now I see on ebay everything thats NOS or Vintage.Ask any collector and he won't touch a 1970's Fender,Yet I see guys pay'n BIG bucks for a Vintage 3 bolt.My favorite peev is Fender in 1982 say'n that they were goimg back to old days of small "real"Fender.Now theres so many modles and $4,000,00 teles that have the bodys sandpapered.Like the SRV guys Don't they know he burned off the finnish.You cant use fuck'n sandpaper and call it VINTAGE but that do I know. dumass

[magna1]

Now i'm hi-jackin

Sorry Regis, to butt in. I think Mark is on the right track tho. Waaaay over my head in the techy stuff, but ive got good seasoned ears, and in the end ya make a choice to tweak or play, or a little o both. I dont have the knowledge or background (yet?) to do much tweaking, so i comment mostly in regard to end results, .... the sound. I think Mark is right on in that i too think that you with a good , ie. quality, appropriate, and in specs chip will get much more with changes in the other aspects of the circuit. (Although i have heard an old yellow with a newish 4558 chip, and i did not like it. It seemed more hi-fi, and thinner). Could it be that on paper the specs are there, but in reality it is produced more efficiently with slightly different formulas in the materials themselves? The 308, and current 250's are pretty different from the old circuit, and to make it sound like an oldie- if thats the goal, than ya gotta get back to that circuit. That being said, i cant back it up techno wise, but i do hear or FEEL a difference in chips 741,351, tl's etc. VERY subtle, but in an otherwise same circuit one will be slightly looser, one tighter or stronger etc. I have to admit that the tolerances of the sum of all the components could have an affect on this. But i still feel that there are suble but discernable differences. I have an old grey with a ECG941, that is amazing!! I dont even know if it's oem or not but i love it in the presence of the rest of this magical little circuit. These companies did some crazy purchasing in those days, i guess at times what ever was availible made it to the production lines.