The classic '70s overdrive by MXR, and is essentially the same as the DOD 250 and Ross Distortion. I designed the layout to have onboard pots, to alleviate some offboard wiring. It also has the LED resistor on the board, again to reduce offboard wiring a bit.
It'll fit perfectly in a 1590B enclosure. Might be a good idea to socket the diodes. The original had germanium diodes, but silicon diodes or LEDs will sound good as well (just different).
the 10pf cup has no through holes in the layout, i just placed it with the 1m resistor next to it, did the rest just like in the layout, BUT its not working ! :/ too bad! i hatched it and everything, maybe theres a mistake in the layout somewhere (its not my first pedal, so its not an idiot soldering mistake from my part)
ReplyDeleteFixed and updated the PCB image. Went over the layout again against the schematic and it should work. Wonder if you've got a bad component or a copper bridge somewhere. You go over everything with a multimeter?
Deleteill try to replace all the components, yes i went all over it with the multimeter, and checked for bridges, its killing me i dont understand y its not working for me, i got no signal going out, and when im shorting the circuit with my finger at some places i do get some wet signal... any idea??
DeleteBefore you replace all the components, have you tried using an audio probe to find where the fault is? Here's a link to the method I've used to debug troublesome boards.
Deletehttp://www.diystompboxes.com/pedals/debug.html
thanks man, ill definitely try audio probe, BTW, i don't have a rev log pot so i'm using a regular one, that couldn't be the reason its not working right?
DeleteYeah, that won't keep the effect from working. The rev log pot just allows better control of the distortion.
Deletewell, i did the audio probe, the input (leg 3)of the opamp receives signal, but nothing on the output (leg 6) on all the op amps i have what can it be ? (there is nothing no where else on all the board except from the input until leg 3 of the opamp)
DeleteAre you using a 741 opamp or something else?
Deleteiv'e tried a ua741 and tl071, more then one from both
Deletewhat dose the new Diod4001 from 9v to 1uf Tant do ?
DeleteThe 1N4001 is just for polarity protection.
DeleteI'm not sure what else to tell you. I had the random thought that if you're using a socket for the IC it might have a short or broken connection in it, but that seems unlikely. Post some pics of the board if you can.
holly fu*** sh** http://diyaudioprojects.com/Forum/viewtopic.php?f=10&t=5015
Deletemy single opamp with UA741CN written on it is actually a dual opamp!! so so sorry for all the trouble, the MXR works fine! i connected one opamp from the dual and it works, and even sounds very nice! :) thanks a lot!
Glad you got it sorted out. Didn't know they made dual 741s. Good to know. Thanks for the verify!
Deletethey dont really make a dual 741, they're just marking 741 on a dual opamp, (some sort of a lame counterfeit) and thank you !
Deletethey dont really make a dual 741, they're just marking 741 on a dual opamp, (some sort of a lame counterfeit) and thank you !
Deletefor original part https://www.youtube.com/watch?v=g59a7S7B128
ReplyDeletefor mod part https://www.youtube.com/watch?v=75TVqVDlCt8
ReplyDeleteAre tantalum capacitors polarized?
ReplyDeleteIn this layout do not show the polarity.
DeleteThe negative leg of both tantalums faces the potentiometer side of the board.
DeleteTHANKS!!!
DeleteCan i use electrolytic instead of tantalium
DeleteYes
DeleteIf someone could help me, please... I can't see the location of the 4001 diode...
ReplyDeleteHuh. Apparently I forgot to copy that diode over from the perf layout to the PCB. You can leave it out as it's just the polarity protection diode. Or you can add it off board going from +9v to ground (cathode to +9v).
Deletethanks!! I´m gonna do the second way, thanks again!! :D
DeleteIs that a typo on the green caps should they be nf not uf
ReplyDeleteOh wow. Yeah old typo. Haha Definitely nF
DeleteAny good replacement for rev log pots? Can´t find it anywhere in
ReplyDeletemy country. Thanks!
Try using a linear 1M pot instead.
DeleteThanks!!! Love you blog! You are the man! Keep the awesome work!
DeleteBy the way is there any recipe for rev log pots replacement like "change it for a double resistance linear pot"? As you suggest in this case? Thanks again!
That doesn't always work... Really depends on the circuit. You can just use a similar value in a linear taper, but there's really not much of a work-around for a rev log pot other than experimenting.
DeleteI see! Thanks again!
DeleteHum, I´m having a problem when I activate the effect. The pedal doesn´t sound right after being stomped. What could that be?? I replaced everything but the 10pF cap. Does it something to do with my issue?
ReplyDeleteTime to learn how to debug!
Deletehttp://www.diystompboxes.com/pedals/debug.html
Well, I checked everything before making the audio probe. With the audio probe I noticed that everything in the circuit was ok. I was so desperated because I couldn´t find the answer even with the probe, when I realized that Ididn't check the switching part of the pedal. For some reason I can´t remember, I didn't make the right connections, I was using a diagram I found somewhere else on the net. And for some weird reason I noticed that, when switched on, the signal was pasing through the circuit signal and the bypass signal. I´m trying to figure this out yet, but I can´t really say exactly (yet, I hope to revise the old connection and come to a conclusion) wha was going on. Thanks for the advice, it helped me to think about the effect as a whole and not only focusing in th circuit part of it. :D
DeletePlease help! Have made two of them now. #1 has no distortion and distortion pot does nothing. #2 has full distortion and distortion pot does nothing. Have tried a500k pot for distortion on both pedals. Makes no difference.
ReplyDeleteYou should be using a C500k (reverse log)
DeleteThat's what I tried at first. Tried a500k just to see what happened and no difference. Weird how they both do it. Could be from my leaving out the 4001 since it wasn't on the pcb or something? The distortion pots don't do anything.
DeleteI have the same issue with distortion not responding, it even started smoking lol. I don't have a 1M pot at hand to try, and my 500k is linear.
DeleteHi,
ReplyDeleteIs it ok to use LM308N (Proco Rat) IC instate of LM741, it can be used?
and how it will sound by 308 i saw you tube proco Rat Mod and realized that this mod can used in MXR, i saw Both ic pin out are same, please suggest.
thank you.
Google is probably your friend there. I've not seen anyone do that before, but I haven't looked either.
DeleteOk sir, ill experiment it i have made this circuit but just searching on you tube i found this mod for proco rat, and i realized that ic make drastic change in sound hence i got this silly idea for mxr distortion plus, sure ill try and get back to you. tnks for quick reply.
Deletetnks.
Hi!
ReplyDeleteI have a question: on every schematics of this pedal Volume pot is A10k? Is there a reason for A100k pot?
Many thanks, pedal-friend!
In my experience you get better control with the 100 over the 10. Either will work though.
DeleteIn my original mxr (I think from 90's) it's a 47K Log ;)
DeleteHello, i can't find any 100k LOG pots in my country, any good replacement for volume pots ?
ReplyDeleteonly LIN pots commonly found here
DeleteLIN pots will work ok too.
DeleteI´ve Noticed that there´s a mistake on the Green Caps Label. they got thier values in uF but they are nF in real.
ReplyDeleteIs there an issue with the caps? Did everyone just change them to nF or is this reply in error? Thanks
DeleteIt's working?...
ReplyDeleteVerified
ReplyDeleteThe 1uf(green caps) should be 1nf(.001uf)
ReplyDeleteSigh...so ALL of the green caps should be nf??? (NOT uf???)
ReplyDeleteOh man, I'm just now noticing the typos. The yellow caps (which are supposed to be tantalum) are the only ones supposed to be uF. All the greenies are nF. Really though, just use the Drivestortion layout. It's way better.
ReplyDeletehttp://effectslayouts.blogspot.com/2015/10/the-drivestortion-project.html
Since C500k it´s a hard to find in some places I have been doing some simulation in lt spice and breadboard testing. The great Wampler Mods uses a A1M and 1k to increase the gain from 46dB (original) to 60dB (which is too much for my little 15w amp). The filter is made for the 1k and 220n, this way the 720 Hz is manteined in the high pass filter (original is made by 4.7k and 47n). So here you´ve got some values for using diferent potentiometers values keeping the cut at 720 Hz:
ReplyDelete1meg = 60 dB
500k = 54 db
250k = 48 dB
The 250k potentiometer is more likely to the original in lt spice frecuency renponse graph, much more with 1.5k and 150n instead 4.7k and 47n.
For me.. ...A500K pot/1k Resistor/220n Cap, sounds the best in my amp.
Saludos desde Venezuela
Which can i use UA741 or JRC4558 or both instead of lm741?
ReplyDeleteUse the UA741. It's the same as LM741.
DeleteCan i use d1 and d2 4001 or in5817?i canot find diode which u listed..
ReplyDelete4001 would work. I generally use 4148s
DeleteThanks i really thought i need that 1n34a germanium diodes if 4001 works it awesome.. thx ur the best
DeleteMy first built worked just fine.. but when i made second time there is no sound .. i rechecked all joins everything is fine but when i touch solder joints of resistor when lies below IC. I can hear distortion. If i leave my hand again theres no sound
ReplyDeleteAny suggestion of help? I did check continuty its just find in all leads
Time to learn how to use an audio probe for troubleshooting:
Deletehttp://diy-fever.com/misc/audio-probe/
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ReplyDeleteIs the orientation of the pots depicted in the layout shown from the back of the pot? ie the legs go 3 2 1?
ReplyDeleteCorrect
DeleteThanks!
DeleteI know it's a distortion circuit, but I wanna make it as a clean preamp. What should I do to tweak this circuit? Please help.
ReplyDelete