# Distortion 250 (Gray Specs)



## Jovi Bon Kenobi (Aug 27, 2019)

Oh wow I love the sound of this one! I built it to 70s gray box specifications with the help of Mr. PedalPCB.


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## geekmacdaddy (Aug 27, 2019)

sweet and neat


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## Chuck D. Bones (Aug 28, 2019)

Very clean.


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## K Pedals (Aug 28, 2019)

Jovi Bon Kenobi said:


> Oh wow I love the sound of this one! I built it to 70s gray box specifications with the help of Mr. PedalPCB.
> View attachment 1144
> View attachment 1145


Nice!!!
What are the substitutions???


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## Jovi Bon Kenobi (Aug 28, 2019)

Thanks folks! Here are the gray spec subs from Mr. PedalPCB.

Add 25pF cap across R2

R3 47K
R5 470K
R6 20K
R7 20K

C1 2n2
C4 22u (positive lead in left pad)
C5 2n2
C6 10u

D1 1N4148
D2 1N4148

Gain C500K
Volume A10K *I used an A100k here*


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## p_wats (Aug 28, 2019)

Nice! Looks great. The 250 circuit was the first pedal I built (from BYOC many moons ago) and it's still on my board.


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## K Pedals (Aug 28, 2019)

Jovi Bon Kenobi said:


> Thanks folks! Here are the gray spec subs from Mr. PedalPCB.
> 
> Add 25pF cap across R2
> 
> ...


Thanks!!!


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## jjjimi84 (Aug 28, 2019)

Awesome work, super clean and neat.


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## Mourguitars (Aug 28, 2019)

jjjimi84 said:


> Awesome work, super clean and neat.



Again what he said !

Mike


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## Angershark (Aug 28, 2019)

Nice! A good example for a beginner like me to reference. I'm actually doing this build right now but according to the build docs. I'll have to try this variation on a later build. I noticed you used a 1uF electrolytic. Is that for this variation that you did on this build? I used a 1uF poly film box in that spot. Will that work or did I make a mistake?


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## Jovi Bon Kenobi (Aug 29, 2019)

Angershark said:


> Nice! A good example for a beginner like me to reference. I'm actually doing this build right now but according to the build docs. I'll have to try this variation on a later build. I noticed you used a 1uF electrolytic. Is that for this variation that you did on this build? I used a 1uF poly film box in that spot. Will that work or did I make a mistake?


Thanks! You'll be fine. Thats a 22uF in the 1uF silkscreen spot, as the mod suggests. I just followed PedalPCB's list to turn it into gray DOD specs. Following the build docs I believe it's closer to a Distortion+.


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## Angershark (Aug 29, 2019)

Thanks for the reply. I've been doing this for about nine months now and learn something new everyday. I will definitely try the 250 variation.


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## Mourguitars (Aug 29, 2019)

Angershark said:


> Nice! A good example for a beginner like me to reference. I'm actually doing this build right now but according to the build docs. I'll have to try this variation on a later build. I noticed you used a 1uF electrolytic. Is that for this variation that you did on this build? I used a 1uF poly film box in that spot. Will that work or did I make a mistake?



Agreed with for a reference , awesome build and very clean work...

Mike


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## Mourguitars (Oct 4, 2019)

Can you swap out the A10k to A100k to add more volume on the reg 250/distortion with out the other mods ?

Mike


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## Jovi Bon Kenobi (Oct 4, 2019)

Mourguitars said:


> Can you swap out the A10k to A100k to add more volume on the reg 250/distortion with out the other mods ?
> 
> Mike


Someone else with more electronics knowledge will have to chime in here. I just added the a100k because that's what all the gray spec mods I found on the interwebs suggested and what was posted above from Mr PedalPCB was very similar to everything I found (minus the a10k) so I went with it. It works perfectly and sounds great.


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## Chuck D. Bones (Oct 5, 2019)

Changing the VOLUME pot from 10K to 100K won't increase the volume.  The diodes will get hit a little harder, that's all.  If you want more volume, your best option is to put a booster after the Distortion 250.  You can change the diodes to silicon or LEDs, or stack 1N270s to get more volume, but any of those changes will alter the sound. 

One a slightly different topic, if you socketed the opamp, you might try other single opamps to see if you like their sound.  741's are _shitty little opamps_ IMHO. They are not low-noise by any stretch of the imagination. They were used in vintage pedals because they were cheap and there were not a lot of options back in the day.


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## Mourguitars (Oct 5, 2019)

I found this in searches, my thought it may come in handy , ill swap out a few IC's

People like running a 10 band EQ after the 250  Dist + like Randy Rhoads did...ill try a clean boost  as well


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## Jovi Bon Kenobi (Oct 5, 2019)

Mourguitars said:


> IC op-amps characteristics
> 
> 
> So since there are so many op-amps (dual, low noise) that you can try in the IC socket of your favorite OD pedal, I decided to write down how I would describe their characteristics so you can decid…
> ...


Nice link. Though those are all dual op amps and I'm pretty sure it won't work in the 250 because it needs a single op amp.



			741 Pin Compatible Equivalent Op Amps


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## Mourguitars (Oct 5, 2019)

Jovi Bon Kenobi said:


> Nice link. Though those are all dual op amps and I'm pretty sure it won't work in the 250 because it needs a single op amp.
> 
> 
> 
> 741 Pin Compatible Equivalent Op Amps



Oh man great catch..i took it down don't want anyone to fry their pedal...Thanks JBK

Mike


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## Mourguitars (Oct 5, 2019)

ElectroSmash - MXR Distortion + Circuit Analysis.
					

The M-104 MXR Distortion + aka Distortion Plus aka D+ is a distortion guitar pedal designed by MXR and released between 1978 and 1979. The original stompbox did not have external power jack or indicator LED. Jim Dunlop bought the MXR licensing




					www.electrosmash.com
				




This is a good read..im starting to understand  things a little more it broke down what parts are in the clipping stage , Op amp stage and Power supply stage

Bookmarked that link JBK

Mike


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## Chuck D. Bones (Oct 5, 2019)

ElectroSmash is a good site and most, but not all of the analyses are correct. There are some errors / omissions in the Distortion+ analysis, but for most part, it's correct.  The opamp does most definitely clip the signal at moderate to high gain settings and the diodes do nothing to stop that.  The input impedance calc is wrong, but it's close.


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## Barry (Oct 5, 2019)

Great looking build as always


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## cgreg714 (Aug 31, 2020)

Jovi Bon Kenobi said:


> Thanks folks! Here are the gray spec subs from Mr. PedalPCB.
> 
> Add 25pF cap across R2
> 
> ...


 Just out of curiosity, what does "add 25pF cap across R2" mean? I'd like to do this version of the build, but I'm new to all this and not sure what this mod means.


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## Barry (Aug 31, 2020)

cgreg714 said:


> Just out of curiosity, what does "add 25pF cap across R2" mean? I'd like to do this version of the build, but I'm new to all this and not sure what this mod means.


You're going to wire it in parallel with R2


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## BurntFingers (Aug 31, 2020)

cgreg714 said:


> Just out of curiosity, what does "add 25pF cap across R2" mean? I'd like to do this version of the build, but I'm new to all this and not sure what this mod means.



You can literally solder a 25pf cap to the resistors legs so they're in parallel. 1 leg each side. Just Google images for 'treble bleed' and you'll see.


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## cgreg714 (Sep 1, 2020)

BurntFingers said:


> You can literally solder a 25pf cap to the resistors legs so they're in parallel. 1 leg each side. Just Google images for 'treble bleed' and you'll see.


Thanks....the google images search cleared it up entirely.


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## Mcknib (Sep 1, 2020)

Now that's a thing of beauty


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## Route14 (Oct 28, 2020)

Was the 25pf cap mounted on the resistor from under the board? I didn't see it in the pics.


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## Jovi Bon Kenobi (Oct 28, 2020)

I sold it ages ago and forgot already, but zooming in close I can see two leads poking through R2's pads so I'm gonna have to say yes


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