Guitar pedal request
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GuineaMcPig

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Hello everyone!

I am a guitarist and am looking for ways to save money on some of the effects that I would like to be able to use. There are tons of vintage pedals out there that sound much better than anything currently in production. One of these pedals, the DOD 440, goes for an arm and a leg on eBay. But I found the schematics the other day and was wondering if somebody here might be willing to try building it. It would be nice if that person were also an electric guitar player so that they would be able to test it.

I would pay for all the parts and labor. Please PM me if you can help. Thanks!

~Jordan

 
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ginettaman

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Have look here,
http://www.generalguitargadgets.com/v2/

this is the site i use for effects, they supply PCB's if you need them, I etch them myself. And in some of the effects there is very little in the way of components.
They are ideal for the beginner to build.

Alan.
 
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GuineaMcPig

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That site looks really useful, and it appears from reading it that the DOD 440 is a pretty simple circuit, but the problem is that a) I don't know how to read a wiring schematic, b) I have never soldered anything before, and c) I don't have a soldering iron. It does look like this wouldn't be too much of a project for anyone with the right tools and knowledge, however. Anyone interested?

~Jordan
 
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groggory

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why is the battery negative connected to the 'in' ?
 
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hpn5350

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Quote:

why is the battery negative connected to the 'in' ?


Its the on/off control. Guitar plus are mono. So when you stick the plug into a stereo socket, it would complete the circuit.
 
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GuineaMcPig

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To be honest, I'm already lost.

If those schematics are incorrect in some way, I think the ones on the site that ginettaman listed are a bit more comprehensive.

I'm sure this would be a pleasant evening project for one of the guitarists on this forum. It might be a nice change from a headphone amp, and I would pay you! Please!
 
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hpn5350

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I am sure you could build it yourself, after you learn some basics! Try starting with a simple project such as theElectra Distortion. Then work your way up to higher level projects.
 
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GuineaMcPig

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I would really like to build one of these, but aside from not having the know how or the parts, I live in a dorm room and don't have the space. I appreciate everyone's help so far, seems like there are a lot of DIY pedal builders out there...anyone on this forum?
 
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stereth

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Lose that extra pot connection (in green) - it's used as a variable resistor to ground.
 
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groggory

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Ok, so let me just try and figure out the circuit. Please tell me where my errors are....

The 'IN' socket

mono socket with 2 isolated ground wires
-pin 1, tip : pin 2, ground : pin3, ground
-When a mono plug (as used in guitars) is inserted, the tip portion of the plug shorts to Pin 1. Thereby carrying the signal.....The ground band on the plug shorts pin 2 and three together, thereby shorting the negative battery terminal to circuit ground.

So basically, if you leave this pedal plugged into your guitar rig, it will always be 'on'

TL022 opamp
Documentation on TI website
Specsheet on TI website
-According to the specsheet, it says the opamp cannot run from a single voltage. However the circuit diagram shows -Vcc going to ground. Why do we not need a virtual ground for -Vcc for this opamp?

SW1
Switch to bypass the pedal

R1 & R2 network
-Feedback resistors for opamp.
-Why can't you replace the 4 resistors with 2 110k resistors in series?

D1
The way I drew in D1, won't that be a short to ground. If its a LED, won't that blow up the LED? I'm not sure. All those resistors down the line might make the voltage at that point low enough for a LED, but I have always put a current limiting resistor in series with LED's. I could be wrong here....

R3
I don't know what this does?
Is it linear or audio taper?

R4
I don't know what this does?
Is it linear or audio taper?
 
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