Archive for 2007

Sunday, December 30th, 2007

Op-Amps 3: Between the Rails

Between the RailsOp-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

… more …

Posted by gaussmarkov | Filed in Op-Amps | 1 Comment »


Saturday, December 29th, 2007

Input and Output Impedance

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 …

Posted by gaussmarkov | Filed in Thoughts | 9 Comments »


Tuesday, December 25th, 2007

Op-Amps 2: Hitting the Rails

Water FaucetA 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 …

Posted by gaussmarkov | Filed in Op-Amps | 5 Comments »


Sunday, December 23rd, 2007

Op-Amps 1: Description


LM741 ICOp-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 …

Posted by gaussmarkov | Filed in Op-Amps | 13 Comments »


Thursday, December 13th, 2007

Another PVC Amp Stand

PVC Amp Stand Exploded

I admit it–this isn’t specifically about stompboxes. But people who need stompboxes also need amp stands. 🙂 I needed several and it occurred to me that PVC pipe would be a good building material. Scouting around on the net, I found one example: PVC guitar amplifier stand. This gave me some good ideas but I decided to try something simpler. This figure above shows an exploded view of what I settled on. … more …

Posted by gaussmarkov | Filed in Thoughts | 22 Comments »


Saturday, December 8th, 2007

LTSpice AC Analysis with the BMP Tone Stack

BMP tone stack AC plots

One useful application of SPICE is to see how a tone stack behaves. Looking at tone stacks is so interesting that Duncan Munro (Duncan Amplification) wrote a now famous computer program, the Tone Stack Calculator (TSC), in 1999 that is still in wide use today. You can download the Windows application from the Duncan Amplification site. This tutorial shows how to use LTSpice to make the same calculations as the TSC for the tone stack of the Big Muff Pi (BMP). … more …

Posted by gaussmarkov | Filed in LTSpice | 2 Comments »


Thursday, December 6th, 2007

A View on DIY Stompboxes

Try to give due credit to others wherever and whenever you can. If you offer something to the public domain, then do so without expecting any compensation or credit. Everything that you receive in return is a gift. … more …

Posted by gaussmarkov | Filed in Thoughts | 11 Comments »


Wednesday, November 28th, 2007

LTSpice Analysis and the DOD Overdrive 250

DOD250 LTSpice Schem thumbnail

Here is a run through the kind of calculations one can do with LTSpice using the DOD Overdrive 250 circuit as an example. You can download the LTSpice circuit (schematic) file for the DOD Overdrive 250 and related files … more …

Posted by gaussmarkov | Filed in LTSpice | 14 Comments »


Monday, November 19th, 2007

Using a Fab House

Olimex board

One of the moderators on Aron’s diystompboxes forum, Peter Snowberg, has repeatedly suggested using a “fab house,” or a PCB fabrication company, to make PCBs. There are lots of reasons for doing this, including convenience, accuracy, and less pollution. I have been wanting to give this a try and waiting for the right project to do it. And I was not sure which company to try. Finally, I took the plunge by sending a smaller version of markusw’s 9V electric mistress project that I have been working on. … more …

Posted by gaussmarkov | Filed in Circuit Boards | 9 Comments »


Sunday, November 18th, 2007

An LTSpice Tutorial

Learning how a circuit works or designing a new one requires experimentation. Besides actually building a circuit, many people use a circuit simulation program. LTspice/SwitcherCAD III is a free program (download link) that many forumites use. Here is a brief introduction to using LTspice, illustrating a calculation with Ohm’s law. This tutorial first appeared on February 27, 2007 on the pre-WordPress version of this site. … more …

Posted by gaussmarkov | Filed in LTSpice | 17 Comments »


Wednesday, November 14th, 2007

Gator Clone

Gator Layout

Slow gear volume swells with a special trigger option made the PAiA Gator a unique gate. This work-alike uses updated and more common components than the original unit, which is no longer available. … more …

Posted by gaussmarkov | Filed in Circuits | 19 Comments »


Monday, November 12th, 2007

1590B Big Muff Build

1590 Big Muff Pi Build

So dig this: probably the smallest Big Muff you’ll ever see. Chris Gregory (stobiepole) decided to make an all carbon comp version using the Big Muff Pi (Triangle Version) layout. This is a nice example of putting the PCB over the pots. Look at Krister’s Pearl OC-07 Octaver Clone build for another example.  View the image in a new window to see a slightly larger version.

Posted by gaussmarkov | Filed in Enclosures | 1 Comment »


Monday, November 12th, 2007

Ground Pour

This is a multi-page tutorial about creating ground pour on an Eagle layout. The picture above shows an example. Note that the ground copper fills in space underneath resistors R1, R2, R4, and R6. It also runs up under the stack of components on the right and in between the +9V trace and C1. … more …

Posted by gaussmarkov | Filed in Eagle CAD | 21 Comments »


Sunday, November 4th, 2007

A Nice Design for 1590B Enclosures

Some time ago, soggybag (on Aron’s forum) designed a PCB for 1590B enclosures that is very clever. Now the PCB and its image are available on his site, Super-Freq. … more …

Posted by gaussmarkov | Filed in Circuit Boards, Enclosures | 15 Comments »


Tuesday, October 9th, 2007

Octaver Clone

Krister's Pearl OC-07 Clone Build

This is the first octaver for If you have a steady soldering hand, or are seeking a challenge, this is a good one: a Pearl OC-07 clone. … more …

Posted by zeta55 | Filed in Circuits | 16 Comments »


Tuesday, September 11th, 2007

Hot Harmonics

Hot Harmonics Layout

I just revised this one, after noticing some needed improvements. It just shows how layout design improves with practice. … more …

Posted by gaussmarkov | Filed in Circuits | 16 Comments »


Sunday, September 9th, 2007

Hot Tubes

Hot Tubes Build by stobiepole

I have revised the Hot Tubes clone. As it turns out, there was a capacitor missing from the factory schematic … more …

Posted by gaussmarkov | Filed in Circuits | 23 Comments »


Sunday, August 12th, 2007

9V Electric Mistress

9V Electric Mistress

This is a meticulous reproduction of the Electric Mistress by markusw on Aron’s forum. See his post. Markus kindly sent his Eagle files for inclusion on Dig the way Markus converts solder lug pots to PCB mount on his build pictured above. His original project file can be found on here. … more …

Posted by gaussmarkov | Filed in Circuits | 18 Comments »


Saturday, August 11th, 2007

Bipolar 9V Power Supply

Bipolar 9V Power Supply

R. G. Keen’s MAX1044 circuit is the basis for this project. The project itself is Chris’s brainchild: a daughter board to get ±9V from a +9V power supply. … more …

Posted by gaussmarkov | Filed in Circuits | 23 Comments »


Friday, August 10th, 2007


Gristleizer Layout

In this project, Chris (stobiepole) and I have put together PCB and vero layouts for the legendary Gristleizer by Roy Gwinn and popularized by Chris Carter and the Throbbing Gristle. We have verified both and have found no ticking problems in our builds from the LFO. We are planning to use this as a starting point into some new territory with this kind of noise maker.

Posted by gaussmarkov | Filed in Circuits | 49 Comments »


Tuesday, July 24th, 2007

Spring Reverb

Spring Reverb Layout

G. Forrest Cook designed this spring reverb and his online publication is on Chris/stobiepole wanted to do this one and his prototype appears above.

It sounds really clean and natural…almost too good to be a spring reverb. But when you whack the reverb springs – *POW* – you get dub explosions.

Posted by gaussmarkov | Filed in Circuits | 30 Comments »


Wednesday, July 18th, 2007

Green Ringer

Green Ringer Layout

Once there was a friendly comparison of green ringer layouts on Aron’s forum and I laid out a smaller version than this one. Coming back to it recently, I decided to add some space and show off the symmetry of this circuit. is the source of the schematic.

Posted by gaussmarkov | Filed in Circuits | 10 Comments »


Tuesday, July 3rd, 2007

Capacitors: Math

For some time, I have been working on a description of some of the math behind equations that we use for passive filters. I do this kind of writing to check my own understanding, and then I share it in the hope of finding my own mistakes and possibly helping others. … more …

Posted by gaussmarkov | Filed in Capacitors | 2 Comments »


Thursday, June 21st, 2007

Automatic Punch

Automatic Punch Center punches are useful for starting holes to be drilled on a PCB. This one is from Snap On Tools and is automatic in the sense that you press down on the punch once it is in place and an internal, spring-loaded hammer makes the dimple. The Snap On version is more expensive than those at Harbor Freight, but you get what you pay for — even if you get it from Harbor Freight.

Posted by gaussmarkov | Filed in Hardware | 3 Comments »


Monday, May 21st, 2007

Blues Driver

Stobiepole and I are putting this out for comment. This is a Boss BD-2 clone in two versions. Both versions are verified. The schematic source was

We used the J201 for the N-channel JFETs and 2N3904 and 2N3906 for the bipolar BJTs and that worked fine.  Neither are original in the Boss box.

Posted by gaussmarkov | Filed in Circuits | 20 Comments »


Saturday, May 5th, 2007

Desolder Pump

Desolder PumpSome folks desolder with a braid but I have not mastered that yet. This desolder pump (or “solder sucker”) works well for me.

Posted by gaussmarkov | Filed in Hardware | 1 Comment »


Saturday, April 7th, 2007

Dr. Boogey

Dr. Boogey Layout

This is electrictab’s pedal emulation of the Mesa Boogie Dual Rectifier Solo Head. See his schematic at It is a very popular build on Aron’s forum. This layout is a substantial revision of previous ones. It is the product of contributions by many members of the forum.

Posted by gaussmarkov | Filed in Circuits | 206 Comments »


Wednesday, April 4th, 2007


Thor Layout

Designed by! I did this one after helping to debug a layout by Xavier on the forum. Thanks to Will Cote for pointing out a component value error. Stobiepole built the prototype pictured above. Runoffgroove says

The legendary Marshall 100W Super Lead adapted for use as a distortion stompbox. Successor to the Thunderchief project. Schematic and PCB layout.

Posted by gaussmarkov | Filed in Circuits | 23 Comments »


Wednesday, April 4th, 2007

Big Muff Pi (Op Amp Version)

Big Muff Pi (Op Amp Version)

Chris Gregory <> suggested this one. He also verified it and helped improve the layout. His build is pictured. Paul Nelson authored the source schematic:

Posted by gaussmarkov | Filed in Circuits | 20 Comments »


Wednesday, March 28th, 2007


Rat Layout

I sold my original Rat long ago and had to make another. has great layouts and I have learned from them. I always lay the circuit out from scratch and see how different mine turns out to be. Thanks to Henrik Jakobsen for correcting an error in a previous version. The schematic source is

Posted by gaussmarkov | Filed in Circuits | 16 Comments »