Author Topic: A beginner Needs help builing MXR distortion plus.  (Read 38106 times)

Izzy

A beginner Needs help builing MXR distortion plus.
« on: September 25, 2006, 10:24:18 PM »
Hi everybody, I am new to this forum and I hope I will get some help here. :)

This is my first project and I need some help builing MXR distortion plus.

I just went to radio shack and bought almost everyuthing that I needed to build this effect.
But I am still confused about few thing from the circuit diagram.

1. How to ground a circuit in bread board?
2. Can Mxr dist + be made in Bread board?
3. I didnt find 1n741 Ics(Op amps) so I got 1n741CN instead, does that make any diference?


aron

Re: A beginner Needs help builing MXR distortion plus.
« Reply #1 on: September 25, 2006, 10:36:48 PM »
1. How to ground a circuit in bread board?
Just make sure all ground points are connected on the bread board.

2. Can Mxr dist + be made in Bread board?

Yes.

3. I didnt find 1n741 Ics(Op amps) so I got 1n741CN instead, does that make any diference?

I believe it should work.

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #2 on: September 25, 2006, 11:05:10 PM »
Hey Aron thanks a lot. I appreciate that.

But please remember this is not the end, hehe . This is just the begining.. Question will come out in a rapid fire mode soon.

Once again thank you Sir.

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #3 on: September 25, 2006, 11:21:36 PM »
Please Ignore my stupidity, but here's another question.
How do you ground a bread board? I am not that much familiar with using bread board even though I am a second year E.Enginnering student.
Hope some one will answer.

cakeworks

Re: A beginner Needs help builing MXR distortion plus.
« Reply #4 on: September 26, 2006, 08:13:33 AM »
I believe it's like 4 columns of veroboard (strip board) so just connect all the ground points to the ground row
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Re: A beginner Needs help builing MXR distortion plus.
« Reply #5 on: September 26, 2006, 08:38:34 AM »
A breadboard usually has 2 rows going left-right across the bottom, and top (maybe blue and red color).  The little columns of 5 holes will then go up/down.   Spend 5 minutes with the continuity function of a meter and learn how they connect together, it will save you a lot of time!  It makes sense after you think about it.   

IC's straddle the 'line' going across the middle of the board; there's no continuity above and below this line.

Pick a left/right row, call it "ground".   Hook your - terminal of your 9v battery there...all points with a ground symbol will connect to this row  ;) There's your ground for the whole circuit. 

Check out the beginner's forum for lots more information.  This is a great circuit, and a lot of fun, so be patient - you will be rewarded!  :D
MXR Dist +, TS9/808, Easyvibe, Big Muff Pi, Blues Breaker, Guv'nor.  MOSFace, MOS Boost,  BJT boosts - LPB-2, buffers, Phuncgnosis, FF, Orange Sunshine & others, Bazz Fuss, Tonemender, Little Gem, Orange Squeezer, Ruby Tuby, filters, octaves, trems...

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #6 on: September 26, 2006, 11:24:48 AM »
Hey thanks a lots guy. I appreciate every bit of  help.

I went to radio shack yesterday and bought almost everything needed for making  MXR dist plus. The guy here helped me to find all the parts but at the same time he was trying to sell stuff...hehe. SO i was like "I need lm741", and he goes "Ok here Lm741CN this should work" and stuff like that. I hope that should not be a problem.

Anyway MY question is
1.Which potentionmeter should I use?

2.I am not familiar with it, but I have heard there are different type of potentiometer like linear taper, audio taper.
And i read here in the forum most people recommend replacing 1M with 500 k and 10k with 100 K. I want to do this but I want to make sure this should be easy replacement. I mean do I have to change anyother thing to replace these two Pots?


3.And whats difference between 1n271 Germanium diode and 1n271 that are found in radioshack?


4. I found three circuit schematics of Mxr distortion plus. And I dont know which one I am supposed to follow?
can Anyone suggest?

http://img133.imageshack.us/img133/1149/mxrdistpki1.jpg

OR

http://img228.imageshack.us/img228/5526/amxrdistzp7.gif

OR

http://img133.imageshack.us/img133/2097/distplusmod406ue1.gif


Any other further help on building this pedal will be highly appreciated
Thanks

« Last Edit: September 26, 2006, 11:32:40 AM by Izzy »

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #7 on: September 26, 2006, 11:41:44 AM »
5. And one more thing. I was trying to but some cables with only one metal strip inside to connect from breadboard to ,switch,jack...etc from Small Bear Electronics. But I dont know which one I am supposed to use. I dont see any pic there. Can you recommend any from this site?

http://www.smallbearelec.com/Categories.bok?category=Wire+And+Cable


6.
I was given this switch at radio shack and I doubt about it. Since this has only two terminals. Do I need another  switch?
http://www.radioshack.com/product/index.jsp?productId=2049717&cp=&pg=6&origkw=switch&kw=switch&parentPage=search
« Last Edit: September 26, 2006, 11:49:56 AM by Izzy »

Mark Hammer

Re: A beginner Needs help builing MXR distortion plus.
« Reply #8 on: September 26, 2006, 11:53:54 AM »
1. For absolute authenticity, a 1meg reverse-log pot is needed.  Most of what that pot does, though, is not of any great use.  If you are not interested in "authenticity" but primarily are interested in cranking it up and rocking ASAP, buy either a log OR linear 100k pot and use it in place of the 1meg unit shown.  I guarantee it will work just fine and give you 90% of what the original will.

2.  For the moment, ignore the two diodes and cap to ground near the output.  You will see that what you're left with is a 10k resistor in series with the output pot.  In combination, the two components act like a pot that can never quiiiiiiiiiiite reach the last 10k of pot resistance.  If the output pot is 10k, that's half the resistance.  If the output pot is 50k, thats 1/6 the total resistance (10k+50k=60k).  If the output pot is 100k, that's just under 1/10 the total resistance .  So, as you increase the value of that output pot, you essentially get to conserve more of the potential volume of the pedal.  Some would suggest that using a 100k output pot provides too big of a load and will make the next device/pedal in line less sensitive to what the Dist+ can feed it, such that 50k presents the best tradeoff between increase in volume without loading issues.  I use 50k and can recommend it as a good replacement for the stock 10k (which you will definitely find incapable of providing enough volume boost from the pedal).
As for the 1meg pot, because of how it is wired up (as variable resistor) at some point as you rotate it, it WILL have a resistance of 5k, and 50k and 100k, and 500k, and 1meg.  The question is whether ALL of those possible resistance values are of use.  Just about everything greater than 100k or so will generally NOT be of much use to a great many people, which is why the substitution of 100k for 1meg is acceptable.
Though the principle underlying this is true in many cases, it is not true in EVERY case.  As you go along, you'll have a better sense of when you can or can't sub one pot value for another.

3.  ANY germanium diode you can find at Radio Shack (they sell 10-packs of iN34A, I believe) is fine.  Some people (myself included) like the sonic changes produced by using 1N914 or 1N4148, but diodes like the 1N34, 1N60, or 1N270 will produce the stock sound.  You should hear no audible difference between any of those last 3 types.

4. The first one is largely correct, though not necessarily the most pleasing sonically.
The second linked schem is correct but incomplete and really more oriented towards folks who know what's missing from the picture.
The third linked schem is not stock but is based on the original and will produce interesting and slightly different sounds.

petemoore

Re: A beginner Needs help builing MXR distortion plus.
« Reply #9 on: September 26, 2006, 12:18:06 PM »
Anyway MY question is
1.Which potentionmeter should I use?

  Like Mark says, 50k is a 'right value as Vol. pot.
  2.I am not familiar with it, but I have heard there are different type of potentiometer like linear taper, audio taper.
  3.And whats difference between 1n271 Germanium diode and 1n271 that are found in radioshack? Use either/try both [V little if any diffy].
4. I found three circuit schematics of Mxr distortion plus. And I dont know which one I am supposed to follow?
can Anyone suggest?

  http://img133.imageshack.us/img133/2097/distplusmod406ue1.gif
  I'd start with this one, for breadboard though, I'd start by getting the 'basic circuit' without the TC, bypass and Indicator..adding later as necessary
 
 5. And one more thing. I was trying to but some cables with only one metal strip inside to connect from breadboard to ,switch,jack...etc from Small Bear Electronics. But I dont know which one I am supposed to use. I dont see any pic there. Can you recommend any from this site?[ I'm not sure I follow...link isnt' working.

http://www.smallbearelec.com/Categories.bok?category=Wire+And+Cable
6. I was given this switch at radio shack and I doubt about it. Since this has only two terminals. Do I need another  switch?
http://www.radioshack.com/product/index.jsp?productId=2049717&cp=&pg=6&origkw=switch&kw=switch&parentPage=search

  You'll need a DPDT for TB, or 3PDT switch for True Bypass W/indicator LED.
  Aron sell's 3PDT Blue, quick ship too.
 

http://img133.imageshack.us/img133/1149/mxrdistpki1.jpg

Convention creates following, following creates convention.

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #10 on: September 26, 2006, 12:21:18 PM »
I quite didnt understand the resistor being 1/6th and 1/10th the total resistence.

But in simple way, isnt the differerence between 100k and 10 k is that -
10 k lets you start your gain from less gain(clean) and as we increase the gain to max it will have the same gain as 100k but we will have less presision as we will have large range.
And 100k will start its gain from more dirtier (more gain) and as we reach max it will have same gain as 10k but since the range is less we can set out setting more precise

That was just my take?

Am I right? Correct me if I am wrong.

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #11 on: September 26, 2006, 12:25:48 PM »
Thanks to "Mark hammer" and "Petemoore"

I appreciate.

@ Petemoore
I am sorry looks like the Small bear electronics site went down for few mins. It is working again NOW.

And do you have any pic of the one that Aron sell? Whats the price?

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #12 on: September 26, 2006, 12:35:11 PM »
@ Mark Hammer

So that means get -

100k reverse  Log/Linear pot for 1Meg (or is it 500k for 1 M?)
50k reverse Log/Linear for 10K

Right? Just want to make sure before I but it now.

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #13 on: September 26, 2006, 12:58:48 PM »
Can please anyone answer my questions above? I am waiting so that I can go ahead and buy.

At the same time One more question

Do I need stereo jack? OR can I go ahead with Mono?

Mark Hammer

Re: A beginner Needs help builing MXR distortion plus.
« Reply #14 on: September 26, 2006, 01:28:00 PM »
Get a 50k log pot for the output volume (instead of 10k), and either a 100k log or linear pot for the gain/distortion control (instead of 1meg reverse-log).  Both suggestions assume you aren't trying really hard to have an "authentic to the last detail" unit.

Re: 1/6, 1/10, etc....

The 10k resistor that is connected between the output cap and the volume pot is simply more resistance that the signal has to pass through.  Volume pots act by dividing the voltage.  The voltage available at the wiper of the volume pot is a function of the total resistance on one side of the wiper, divided by the total resistance on the other side.  The pot acts as a variable voltage divider but it is no different in function than a fixed voltage divider.  Look at your first or 3rd linked schematic and you will see that +9v goes to a pair of 1meg resistors and what is available at their junction is half of 9v (i.e., 4.5v).  Think of THAT like a 2meg pot with the wiper exactly halfway.

Okay, now consider that the circuit itself doesn't really care of the resistance on each side of the wiper is sitting inside the pot or outside of it.  It's ALL just resistance to be divided up into the this-side and that-side portions.  If we have a 50k pot with 10k of additional resistance soldered on one end, then rotating the wiper aaaaaaaaaaaall the way over to that end still will not be able to place the wiper past that juncion between the added resistor and the pot lug.  You will always have 10k sitting outside the pot.  So, with the wiper fully rotated, there will be 50k of resistance between the wiper and ground, and 10k more on the other side of the wiper.  Add 10k and 50k together, and what you have is functionally no different than a 60k pot that can never quite reduce that last 10k of resistance to nothing.

Again, keep in mind that since the possible volume from the pot is a function of how much it divides down the voltage fed to it, zero-ohms divided by 60kohms produces NO reduction of the signal.  Actually, let me change that, it's 60k, divided by 60k (=1).  If our 60k pot consists of the 10k "external" part and 50k "internal", then the signal can never reach more than 50k/60k or 5/6 of its maximum value.

This principle of how-much-can-you-dial works on both ends of the pot.  For instance, if you look at the schem for a Big Muff, you'll see that there is a small value resistor between ground and the ground side of the "Sustain" pot.  Why is it there?  So that the signal can never be dvided down to absolutely nothing.  That tiny resistor assures that even when the wiper is rotated to the 7:00 position there is still just a liiiiiiiiittle bit of resistance to prevent the entire signal being divided away and bled to ground.

Note that this principle works with variable resistors (two lugs used, no division "ratio" implied) as well as voltage dividers (where ratio of one side vs other side of wiper matters).  In series with the gain pot is a 4k7 resistor.  Does it HAVE to be 4k7?  No.  The total resistance obtainable on the path, when the pot is maxed is the sum of that resistor and the gain pot (whether 1meg, 500k, or 100k or whatever you bought), and the minimum resistance attainable is the value of the fixed resistor (4k7).  the gain of that Dist+ circuit increases as the total resistance on that path gets smaller.    Stock, the max gain is set by the 1meg feedback resistor and the 4k7 resistor ( [1meg+4k7]/4k7 = x213).  If a person changed that 4k7 for, say, 3k9 then the max gain would be [1meg+3k9]/3k9 = x257.  Dropping it further to 3k3 gets a max gain of x304, and so on.

On a number of modulated pedals (i.e., those with any sort of cyclical change), the LFO/sweep-generator uses a variable resistor in series with a fixed resistor to set the speed. Using a similar principle to what has been discussed here, you could easily alter the range of speed values by changing either the pot value, the series resistor, or both.  Let's say we have some LFO circuit that used a 500k pot in series with a 4k7 resistor, and you found that you had little use for most of the range of speeds.  It would not be inappropriate at all to replace the 4k7 with a 10k resistor, and the 500k pot with a 250k or even 100k pot.  Those two changes to maximum and minimum combined resistances would eliminate the slowest and fastest speeds from the stock circuit, and would allow the pot to have finer control of a narrower range of speeds more desirable/useful to you.

Again, the lesson is to learn to think about the total resistance or resistances involved, and use that to tailor what you want the device to do for you..

burnt fingers

Re: A beginner Needs help builing MXR distortion plus.
« Reply #15 on: September 26, 2006, 03:19:05 PM »
Once again Mr. Hammer comes to the rescue on this classic circuit.  I just finished mine using a 1M audio pot wired backwards for the gain control.
 
Good luck with your build, it's a very cool pedal.
 
I do have one question though, what Radio Shack sells 1n34's?  I have never seen them at any of my local Rat shacks here in southern california.
 
Scott
Rock and Roll does not take a vacation!!

www.rockguitarlife.com
My Music

Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #16 on: September 26, 2006, 09:54:14 PM »
Firstly Salute to metal hammer. Thanks for your tremendious help.!

@ burnt finger

No I didnt find 1n34's at radio shack. SO i am going to buy it from small bear electronics.
I think I should keep in touch with you for help.  ;D


At the same time which wires should I get for connecting battery,swtich,jacks?I am looking for wires with only one metal strip inside.

Are these what I am looking for?
http://www.smallbearelec.com/Categories.bok?category=Wire+And+Cable




Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #17 on: September 26, 2006, 10:14:29 PM »
Another question -

1>
Are LED rated? OR can I use any led for this project?
I was just trying to fiddle around trying to make LED lit.I used 1.5 battery and connected a 2.2k ohms resistor in series and tried to lit it.BUt it wont?
WHy is that?
DO I need 9v battery?

2>
I am thinking of using 9v battery outlet of an AC adapter for this project. Will it work? OR is it necessary to buy a 9v battery

aron

Re: A beginner Needs help builing MXR distortion plus.
« Reply #18 on: September 26, 2006, 10:22:31 PM »
I would use a 9 volt battery since this is your first test build. I guess I need to make the STORE link bigger in the future. :(


Izzy

Re: A beginner Needs help builing MXR distortion plus.
« Reply #19 on: September 27, 2006, 12:00:39 AM »
Thanks Aron for your info.

And where am I supposed to but Potentiometer that Mark hammer suggested? I looked in radio shack , small bear electronics, and other few online stores and couldnt find it.
Does anyone know some specific site?