gaussmarkov: diy fx

Creating a PCB Image using Export

gaussmarkov — Fri, 02 May 2008 04:53:15 +0000

If you want to etch a PCB with a layout in Eagle then you will need to create an image like this one to transfer your design. This brief tutorial explains how to set things up so that you can use the Eagle export command. (more…)

Slide Switch Tutorial

stobiepole — Wed, 09 Apr 2008 23:54:24 +0000

When building stomp boxes, slide switches have certain advantages over toggle switches. They are less expensive and more durable than toggle switches, which can easily get broken off by clumsy feet or by mishandling. But they can be trickier to fit, requiring a rectangular cavity to function correctly. Here’s a way to fit a slide switch, using only a couple of simple tools. (more…)

The Noomerang

stobiepole — Tue, 26 Feb 2008 06:01:58 +0000

The Noomerang is a wah pedal by B Tremblay of runoffgroove.com fame. It’s a variant of the Maestro Boomerang wah, which itself is a nice alternative to the usual Cry Baby clones, with some added goodies. (more…)

The Hornby Skewes Zonk Machine

Brad — Sun, 24 Feb 2008 17:23:55 +0000

Yo. Here’s a layout I did for the Hornby Skewes Zonk Machine. I used the schematic from the Fuzz central website. I put an extra pad for the .47 cap since I couldn’t find a package big enough for the Xicon greenie .47. (more…)

Voodoo Lab Overdrive

gaussmarkov — Fri, 11 Jan 2008 23:49:03 +0000

I have various reasons for putting this one together. My interest was peaked when the Voodoo Lab Overdrive was associated recently with the Fulltone OCD. I was also looking for a relatively simple circuit with op-amps that I could use for an Eagle layout tutorial that I plan to write. In addition, I have been working up my understanding of op-amps through writing a series of tutorials and the divided negative feedback tools are really useful with this circuit.

There are a bunch of mods to consider with this circuit, all of which have been applied to other stompbox circuits over the years. And if the reports are accurate, similar mods appear in the OCD as well. (more…)

Op-Amps 4: Divided Negative Feedback

gaussmarkov — Tue, 08 Jan 2008 19:58:13 +0000

Simple negative feedback, connecting the output to the inverting input, makes an op-amp into a unity gain amplifier. In that setup, all of the output goes to the inverting input. If instead the amount of feedback is reduced, through a voltage divider, then the gain of the op-amp circuit becomes greater than one. This may be the most common way op-amps are used for amplification in stompbox circuits. In addition, by adding some capacitors to the voltage divider, the gain also gets some tonal character that is the foundation of dozens of famous distortion and overdrive pedals (think Boss, Fulltone, Ibanez, Marshall, Proco, Voodoo Labs, …). (more…)

Op-Amps 3: Between the Rails

gaussmarkov — Mon, 31 Dec 2007 05:22:26 +0000

Op-amp output hits the rails because op-amps are powerful amplifiers with gains in excess of 200,000. With a 9V single-supply, all it takes is an input voltage difference of 9V/200,000 = 45uV to hit the positive rail. Guitar outputs are around one thousand times that magnitude. So how do you keep the output of an op-amp between the rails? You use feedback.

Photo credit: Mike Malak on WikiMedia Commons

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Input and Output Impedance

gaussmarkov — Sat, 29 Dec 2007 15:37:00 +0000

You have probably heard or seen it said that high input impedance and low output impedance are desirable properties for a circuit. Or at least something like that. Maybe it was the other way round, as in low input impedance and high output impedance? I found it hard to remember before I had some grasp on the concepts. This note describes the understanding that I have so far and a practical way to measure impedance. (more…)

Op-Amps 2: Hitting the Rails

gaussmarkov — Tue, 25 Dec 2007 23:46:39 +0000

A first step in understanding op-amps, and amplification generally, is to see that op-amps are like a water faucet that controls the water pressure in a garden hose. In the simplest setups, the faucet alternates between completely closed and wide open. As a result, the output of the op-amp is either the lowest or the highest available voltage, in analogy with no water pressure or maximum water pressure in the hose. (more…)

Op-Amps 1: Description

gaussmarkov — Mon, 24 Dec 2007 04:26:31 +0000

Appearance

Op-amps (operational amplifiers) come in an integrated circuit, or IC. The one pictured on the right is in a form called DIP-8, which is short for dual in-line package with 8 pins. “Dual in-line” refers to two lines of pins, in this case 4 on each side. Each pin has a special function and they are numbered from 1 to 8. Often, there is a circle on the top of the case to show the location of pin 1. Also the case is usually notched at the same end with half-circle cut-out. At least one of these two markings appear, but not necessarily both. (more…)