Trying to desing a distortion (help needed).

Started by jpm83, August 10, 2007, 03:03:33 PM

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jpm83

This is my first try to design a pedal, so is this kind of pedal allready made and if not will this work? Here is the schemo

Janne

Gus

looks like a dist +/ros dist etc with the gain pot in the other part of the feedback Rs?

Sir H C

C3 is going to roll off some of the low end.

jpm83

Quote from: Gus on August 10, 2007, 03:28:05 PM
looks like a dist +/ros dist etc with the gain pot in the other part of the feedback Rs?

Thanks for answering. I used this site to guide http://www.generalguitargadgets.com/richardo/distortion/index.html and took ideas from a few distortions; dist+, rat, sonic distortion. Is there any obvious misstakes that will need to be fixed.

Janne

jpm83

Quote from: Sir H C on August 10, 2007, 03:35:45 PM
C3 is going to roll off some of the low end.

Would it be too much for the guitar? Would 100nf be better?

Janne

CGDARK

Quote from: jpm83 on August 10, 2007, 03:03:33 PM
This is my first try to design a pedal, so is this kind of pedal allready made and if not will this work?

Why don't you breadboard it. It's the best way to test, change parts values and fine tune a circuit.

CG

jpm83

Quote from: CGDARK on August 10, 2007, 03:45:52 PM
Quote from: jpm83 on August 10, 2007, 03:03:33 PM
This is my first try to design a pedal, so is this kind of pedal allready made and if not will this work?

Why don't you breadboard it. It's the best way to test, change parts values and fine tune a circuit.

CG

That's because I don't own a breadboard and I don't have my soldering tools with me at this weekend, And I don't have the parts right now. Could someone who has a breadboard try if this works?

Janne

Mark Hammer

In the Distortion+, the C3 equivalent will only start to roll off the bass as the gain is increased, and even then the highest point at which the bass is rolled off is around 720hz.  In your configuration, the bass is always rolled off around 3.4khz, which is, um, a little high.  If you increased C3 to 1uf, that would provide a rolloff starting around 160hz, which isn't too bad.  The '-' side of the cap goes to ground.

Although the circuit would still "work" if R5 is set to minimum, "working" would constitute a gain of 1.  You probably want to stick a fixed resistor in series with R5, just to assure that the minimum gain of the pedal is at least a bit of a level boost if not clipping.  A 10k resistor will give a minimum gain of x11, and a theoretical maximum gain of x261, which is a bit over what a stock Dist+ delivers.

Note that with the 100pf feedback cap, you will have a 6db/oct treble rolloff starting around 6.1khz.  That's not bad and is a good first approximation, since you have a variable treble-cut in conjunction with the diodes.  On the other hand, the treble-cut control will not remove very much, and the clipping diodes will add some sizzle.  My own suggestion would be to increase C4 to 220pf, and increase C7 to .0039uf or even .0047uf.  That will not rob you of any bite with the tone set to max treble, but will allow you to achieve nice throaty sounds without having to turn down the treble at the amp.  I can hear it in my head now, and it isn't half bad.

Making C5 nonpolarized will certainly not hurt anything, but it does not need to be NP.  Since you plan on using a dual op-amp, you might want to think of some productive use for the other half of the chip.  For example, you will note that an Orange Squeezer only requires a single op-amp as well. :icon_wink:

CGDARK

Quote from: jpm83 on August 10, 2007, 04:00:20 PM
Quote from: CGDARK on August 10, 2007, 03:45:52 PM
Quote from: jpm83 on August 10, 2007, 03:03:33 PM
This is my first try to design a pedal, so is this kind of pedal allready made and if not will this work?

Why don't you breadboard it. It's the best way to test, change parts values and fine tune a circuit.

CG

That's because I don't own a breadboard and I don't have my soldering tools with me at this weekend, And I don't have the parts right now. Could someone who has a breadboard try if this works?

Janne

For what I seen in the shematic I think the circuit will work, but the question really is, Will you like the sound? ???

CG ;D

jpm83

Quote from: Mark Hammer on August 10, 2007, 04:04:47 PM
In the Distortion+, the C3 equivalent will only start to roll off the bass as the gain is increased, and even then the highest point at which the bass is rolled off is around 720hz.  In your configuration, the bass is always rolled off around 3.4khz, which is, um, a little high.  If you increased C3 to 1uf, that would provide a rolloff starting around 160hz, which isn't too bad.  The '-' side of the cap goes to ground.

Although the circuit would still "work" if R5 is set to minimum, "working" would constitute a gain of 1.  You probably want to stick a fixed resistor in series with R5, just to assure that the minimum gain of the pedal is at least a bit of a level boost if not clipping.  A 10k resistor will give a minimum gain of x11, and a theoretical maximum gain of x261, which is a bit over what a stock Dist+ delivers.

Note that with the 100pf feedback cap, you will have a 6db/oct treble rolloff starting around 6.1khz.  That's not bad and is a good first approximation, since you have a variable treble-cut in conjunction with the diodes.  On the other hand, the treble-cut control will not remove very much, and the clipping diodes will add some sizzle.  My own suggestion would be to increase C4 to 220pf, and increase C7 to .0039uf or even .0047uf.  That will not rob you of any bite with the tone set to max treble, but will allow you to achieve nice throaty sounds without having to turn down the treble at the amp.  I can hear it in my head now, and it isn't half bad.

Making C5 nonpolarized will certainly not hurt anything, but it does not need to be NP.  Since you plan on using a dual op-amp, you might want to think of some productive use for the other half of the chip.  For example, you will note that an Orange Squeezer only requires a single op-amp as well. :icon_wink:

would this be better? And thanks for the tips you're great. :icon_biggrin:

Janne

Mark Hammer

Almost there.  C4 should straddle BOTH the pot and the 10k resistor, not just one of them.

As an aside, note that on the Distortion+, the stock circuit tends to need a gain pot with an "exotic" taper.  This is because the ground leg (represented by the 1k/iuf segment here) has to undergo large decreases in resistance to produce noticeable changes in gain.  In your case, you have used the feedback loop and this easily produces noticeable changes in gain with little effort and no need for pot weirdness.  A standard linear taper pot can be used with success, the same way it is used with success on the TS-9 and Proco Rat.

jpm83


Mark Hammer


jpm83

Great now I just have to order the parts and make a vero layout. Thanks for tons of your help on this one. If this will be worth building you will be mentioned in credits.

Janne

CoolJohnny

i still say the best way to go about this is to buy a cheapo breadboard at radio snack and start pokin.' its the best way to learn how these things work (even if not from a mathematical perspective) and the best way to test your own theories. so a transistor goes pop every once in awhile or a battery gets hot and explodes burning iridescent acid goo on your hands every so often cause you rigged the thing up wrong...its all part of the experience, man.
my car is so slow i piss off amish people....

CGDARK

Quote from: CoolJohnny on August 10, 2007, 11:25:10 PM
i still say the best way to go about this is to buy a cheapo breadboard at radio snack and start pokin.' its the best way to learn how these things work (even if not from a mathematical perspective) and the best way to test your own theories. so a transistor goes pop every once in awhile or a battery gets hot and explodes burning iridescent acid goo on your hands every so often cause you rigged the thing up wrong...its all part of the experience, man.

I posted the same thing, I think it's the best way to test and learn.

Quote from: CGDARK on August 10, 2007, 03:45:52 PM
Why don't you breadboard it. It's the best way to test, change parts values and fine tune a circuit.
CG

CG ;D

jpm83

Here is the vero layout that I just made, so if you're interrested try it out.
The layout isn't verified and neither is the design. If you build this let me know how it sounds.

Janne

oskar

Quote from: jpm83 on August 11, 2007, 10:42:44 AM
Here is the vero layout that I just made, so if you're interrested try it out.
The layout isn't verified and neither is the design. If you build this let me know how it sounds.

Janne
You need to put the unused OP-section to sleep...
output to negative in, positive in to ground...


jpm83

#18
Quote from: oskar on August 11, 2007, 11:11:07 AM
Quote from: jpm83 on August 11, 2007, 10:42:44 AM
Here is the vero layout that I just made, so if you're interrested try it out.
The layout isn't verified and neither is the design. If you build this let me know how it sounds.

Janne
You need to put the unused OP-section to sleep...
output to negative in, positive in to ground...



Like this?
Janne

oskar

Like that... But try and find a creative use for it instead...   surprise us!

oskar