Original DOD 250 Grey Spec layout,and layouts with mods and transfer images

[clamup1]

hey quick ? i breadboarded the 82 schem. on p1 3 hookes to the .047. 1 goes to ground. what does 2 hook to. ive built this before but dont rem where it goes.

[Renegadrian]

Malmsteen seems to use it mainly as a dirty booster. And off course, the rest of their equipment, fingers, playing style etc is different.

Yes the 308 alone does give you YM sound but it hasn't got all the gain needed to get his TM sound...
Basically it gives a good boost at his 50w Marshalls, adding a little on the treble sound. I guess he doesn't use it anymore, at least in studio, as his last recordings spot a dark and muddy guitar sound...I love him as a musician, but he's an awful producer...I listened to a lot of newcomers' demos that sound better than YM last records!!!

[Steve Mavronis]

I agree with you about the bad studio mix on Yngwie's last album. Seems too heavy with the bass EQ to me. He reportedly used a prototype of his new signature Marshall YJM100 amp, which has a 'boost' overdrive built in. They are a little vague about what it actually is, just saying it's to Yngwie's spec from his YJM308 overdrive. I find that hard to believe they would integrate the exact DOD circuit basically cloning it like we do. But they won't identify it by name and the schematic isn't protected so I guess they have the same freedom as we do. But I like the tone of the gray 250 more than his 308 anyway. Can't wait until someone gets the amp and shows us a gut shot of the overdrive circuit. I don't think this is responsible for the bad production sound of the album. It's in the mixing. Very soon Marshall is promising a new demo video of the YJM100 with Yngwie himself playing it using his Strat to show off the features. Then we can get a good assessment of what overdrive is in it.

[Steve Mavronis]

This is interesting. Today after work I compared my gray 250 clone and the YJM308 mod to gray spec side by side. One thing I noticed was that at half way the level (volume) knob setting the YJM308 is louder. I found the reason why. My 250 clone uses a level pot value of A100K which is A for Audio Taper. The YJM308 uses a W100K for its Level pot. I've only seen A=Audio, B=Linear, and C=Reverse Audio log pots for sale online. I was trying to figure out what the W stood for. This is what I found:

If you look at this pot taper comparison graphic below you can see in the bottom left graph when the W taper is at 50% rotation it is at half the total volume range. In the top left graph the A taper has to be at roughly 75% rotation or so to have equal volume output.



Of course you can match their volumes by ear but now I know why.

[Steve Mavronis]

I modded my DOD YJM308 Overdrive to late 70's gray specs. Removed stock KA4558 chip and replaced with socketed LM1458N (dual 741 op amp), removed C2, and replaced the 0.001uF input capacitor C3 with a 0.01uF value per spec. I used fine braid size #2 solder wick and it worked so good de-soldering the parts that they literally fell out of their holes. Simple and done in less than 30 minutes!



I finished off the mod with original DOD style fluted knobs! Sounds freaking great now. I decided not to cut traces and re-route wires just to use a single 741 chip. The 1458 op amp has two 741 circuits inside and using one of them so it is technically still the same. Comparing noise levels to a gray 250 clone I can't hear any difference to make it worth doing the so-called 'mojo' mod.



I've been meaning to do this for some time. Only thing 'optional' I could add is true bypass 3PDT footswitch, LED, and Boss style power jack, and maybe re-decal it to say YJM250.

[Steve Mavronis]

Something I've always wondered about: What were the 2 part holes (near the bottom on the old 250 PCB in the photo below) originally used for? I think there is a clue. Most everyone knows the 250 was based on the 70's MXR Distortion+ circuit. It's virtually identical except for component values, and one extra part! On the Distortion+ PCB there is an extra 0.001uF cap connected right after the input pad (before the 0.01uF input signal cap) going to ground.

On the 250 this is missing, with the apparent empty pad holes for it located in between the 0.01uF input cap and 10K resistor, going to an empty ground pad hole. Funny after all this time I only realized what this was probably for after reading an Arctic Fox Audio blog article (http://www.arcticfoxaudio.com/blog/articles/7/reducing-noise-in-the-mxr-distortion)
about "Reducing Noise in the MXR Distortion+" that caught my eye. I'm interested in trying out the author's technique for reducing noise by half. It seems that to achieve this he decreased the resistor values and increased the cap values to preserve the frequency response, but the pedal didn't sound the same at all. But he got that corrected by changing this 'input cap to ground' back to its original value.

In the case of the 250, or any circuit, would the actual placement of this missing cap matter if it would be located 'before or after' the input signal cap? I might try this on one of my extra clone boards and if it works make a new modified noise reduced version. Of course the begging question is why DOD made their PCB including these part holes and why didn't they actually use it?

[Herb1962]

Hi guys, hoping someone can help an old fella out... Apologies for bringing up an old thread... I am hoping to put together a grey spec 250 like I used to own back in the day. I put together the layout at the top of front page provided by Brymus (without mods) Has this layout been verified by anyone else? I'm not getting anything, but I don't trust these eyes so much anymore... I've put together quite a few pedals and amps over the years so I'm relatively confident.. Great thread by the way for a very under-rated pedal!!

Herb

[dimirock]

Hi guys! I've build this great pedal based on this layout:
http://www.sabrotone.com/?attachment_id=2467
Is it possible to mod the flabbiness of the lows?
Also is it normal to put the Level around 3 o'clock to match the bypass signal? The level is too low.


Here is a demo with the pedal without any modifications, build strictly on Sabrotone's layout.
https://soundcloud.com/diminalbantov/guitar-rig-5-marshall-plexi-50-diy-250-boost

[LightSoundGeometry]

I do want to reply! no need to start a new thread?

I have never heard on of these in person..or have I lol ? what guitarist uses one on what song? I might try to make of of these as i have the parts here on hand at home

[petey twofinger]

spent more time with this circuit over the last year . th customs sells a OD 67 pcb with all of the Brian Wampler mods from the article featured in premiere guitar . i built my own version of this Wampler mod 250 and auditioned those mods to chagrin, as ultimately i found the 250 is best served stockish but with custom clippers.

i wanted to mention something i found which i read in this thread about the 25pf C2 as it is listed on the Marvonis chart (Thanks Mr.Marvonis )  . if one looks at the DOD schematic , it shows a 120pf capacitor in the feedback loop of the op amp , so this is the feedback capacitor .

i found thru my experimentation nasty loud HOWLING feedback if i was running the circuit outside of a chassis with much RF interferance / oscillations due to longer runs of  unshielded test rig wire etc , it was of utmost importance  to utilize this capacitor to avoid feedback and howling when the gain/volume knobs are above noonish . one can merely run a 47pf-120pf comfortably without worrying about cutting into the guitars treble frequencies too much . in the past when i have made these circuits on a vero layout i typically just prema-install a cap with a value of 100pf here , to feel nice about myself as i also realize this is nice to have even when using the slow slew rate dirty stinky hated noisey 741 . not to contradict any one , but in my experience i do utilize that capacitor no matter what ic chip i choose to install to enjoy stability / noiseless operation .

op amps matter in this instance. to my ear ANY 741 is the winning choice . this is especially evident when running the circuit sans clippers as this the distorting on its own 741  chip is doing its job  and thats where the magic sits in this circuit , using the right clippers for your rig / ears and most importantly using a slow slew rate nasty old 741 .


i do not intend to contradict folks but in my testing i heard differences that were percievable to the point of me choosing one chip over another , they are not large enough to seek these out , but  i will say the 741 in every itteration was superior to evry other chip that we ran .

the metal can ray741 actually does sound a bit less raspy and has a slight more bit of oomph between the 741ua chips i pitted it against but todays testing show the authentic lm741cn vs the metal can circa 79 ray741 was in fact the top peak sounding winner for just a smoother less raspy and having that special something in the way the distortion sounded with chords and single note playing as we did a repetitive series of tests with different phrasing /chords and notes to fully hear everything we could think of and be fair . the metal can has something undefinable but i would call it tightness and a smoother more pleasant break up .

chips to avoid -

using a lm308n /tlo71 in it and its much more pristin-ie and harsh ice pickie fizzish distortion as it lost its magic , which is quickly regained when the 741 chip is in place . testing done with high output humbucker guitar >DoD250(powered by fresh 9 volt ) >jc 120 clean channel eq maxed , bright off and also on , low channel input .

as far as clippers go , two red 3mm leds are where you start. one ear which i would say is trained ( you may have some of his music in your collection) ended up choosing a red 3mm led combined with a 1n4148 .

using the 250mod w/two red led's and setting this circuit "nooned" is my favorite way to play ,its always on unless i am going for a high gain deal, and man it sweetens everything  , its very uncompressed clean and only grits when i dig in with a very unique grit that fits on top of the clean not like that unpleasent effect of a lm386 set to low gain . this raspy distortion does sit above the clean but it fits and belongs as one , feeling so pick responsive and also sounding natural its something i have yet to find in any other circuit _ (this as described is only obtained using two 3mm red clippers and nooning the controls)-

typically most folks run this circuit much more like a dirtbox with diodes installed instead of leds , or if they are using leds they crank thegain higher ... i have to admit this was a mod gone bad that was on my board and i stumbled on it literally kciking the mod switch on accident then going wow wtf is makin that ?> lol .


i recently found using a single (or two)  led and then a 1n4148 diode it really shines as a truely transparent or do no wrong med gain od when we again set at noon as well . it does "nothing bad" as one very valued ear put it .

i am going to be spending time attempting to pair an led with a diode or some new perfected combination of clippers as i have yet to even mossfet ... but my goal is to get closer to flexible overdrive that does the odball two leds set nooned is really more subtle trick that i like very much / have been using this for years now as it is my favorite most used build ,and then having the mod switch convert this to the other idea of a more pronounced overdrive . so all time wasting and path searching aside , one could just vero up a stock 250 , maybe boost the bass cap (.047uf to a .22uf per mark hammer "improve led clipping response in a led mod 250" idea quote  ) use a 741 chip , then throw two red 3mm on one side of a dpdt and a1n4148 / 3mm red led on the other and be just deal with a volume difference .

the idea of having a Mod switch that one actually chooses to engage and use the other setting would literally be a first as i have to admit in most cases the mod switch is an embarrassing redundancy that is always left set to the right (or left) . i am hoping to go thru some componants and perhaps improve upon the combo i mentioned which was two red 3mm leds set facing with the anode / cathode properly aligned and then the 1n4148 was reversed in between the two . this was an error , but the guy loved it ,and asked for a 100 percent clone as a back up . ha . so i am going to be looking into that and perhaps create something for myself .


as far as the wampler mods and every other mod for this circuit , every single thing i have tried (exception of using led clipper or led combined with a diode and then using the 741 chip) has taken the circuit in a direction i felt was opposite from what i really love about it . what is that ? use a 741 , and  a single 3mm red combined with a 1n4148 and you will know for yourself . if you love that consider the double 3mm red led , although i am on a path to experiment for something different as far as the dual led clipping goes .

read up and see what the pros techs and experts say about the 741 chip " why would any one dream of using this outdated turkey dirty stink chip that is a dirty bastard that even distorts  - - - - um may i have one of those please as i am building  a distortion ?

additional harshness and noisy noise can be tamed with the 0022uf cap placed to ground after the clippers as shown in the grey spec layout .

if one is using led clippers Mark Hammer mentioned to consider modding the .047uf (c1) bass or input cap to a .22uf - something i am considering but with the  led mod i use i never set the gain more than noon , i am happy with the clipping ,still i would like to hear the mods / am curious and feel the time is well spent as i have such a huge spot for this circuitin my heart .  so i should really try this as well as changing the gain by a resistor swap tied in with the control . - MHammer - stuff from another thread -  additional harshness and noisy noise can be tamed with the 0022uf cap placed to ground after the clippers as shown in the grey spec layout .


TLDR ,

you HAVE to use a 741 chip or kittens will perish ,

socket the clippers, try 3mm red leds , or try 3mm red w/ 1n4148- (2 leds = less compressed more open . Led/diode combo is less subtle but natural od tone with "no bad"

use a feedback cap or C2 (on the marvonis chart) c2= 47pf or more  up to 120pf) to avoid oscillation

if you dig the led clipping butneed moar consider mark hammers comment(s) about uping .047uf to .22uf for more clipping from LEDs - there is more on this from Mr H ....