New at GEO
    GEOfex | R.G. Keen

1/4/09 OK, I updated the Bass Brassmaster PCB layout based on some new info. Here's the poop, for checking.
9/17/08 Updated - Panning for Fun; now includes a circuit for panning one input to two outputs.
7/23/08 Thoughts on amplifier hum sources.
1/22/08 I always wanted an AC30 head. Never found one, but I did find the measurements of the AC -30 head cabinet. I'll post more detail as I draw it. Latest update 1/28/08
12/18/07 Traced out the Boss PH-1r phaser schematic while doing some research.
8/02/07 Updated - the Fender Pro Vibrato; added gain stage for those with low gain JFETs.
8/01/07 For you pickup winders - a Pickup Tester to go with the conceptual CNC Pickup Winder. These are currently only at the concept stage, but a skilled builder should have no trouble making their own.
6/30/07 It's BACK!!! My PCB layout tutorial "PCB Layout for Musical Effects" is now available again. For a quick look at what it contains hit the link just above. If you already know you want a copy, go to Small Bear Electronics and grab one! The first hundred copies are personally signed by the author (that's me... I have writer's cramp!)
5/9/07 New - another emulator of the Fender Pro vibrato
3/8/07 New - a solid state emulator of the Fender Pro vibrato
11/16/06 New - a Modular Phaser based on the JFET phasers like the Phase 90.
10/24/06 New - a Leslie style ramp/up down LFO adapted for the Phase 90
10/23/06 New - a Leslie style ramp/up down LFO, adapted for the Easyvibe.
8/25/06 Updated - the Tychobrahe Parapedal schematic and layout (pdf) / Newparapedal.pdf - local. The board bolts into a Crybaby shell and clones the Parapedal. Fixed a capacitor bug and added a new negative ground version.
6/24/06 Updated - there was a bug in the wiring diagram for the Neovibe. That's corrected in this write up. Notice that the write up at General Guitar Gadgets will still have this error until it gets updated as well. If the resolution is still not good enough, check this schematic and wiring diagram.
10/31/05 Lead dress in tube amps - learn the principles behind what wire goes where.
2/14/05 How to solder - step by step.
12/8/04 A quicky - updated hum free splitter/A/B/Y
8/28/04 A new CMOS Pseudorandom generator for noise and sequencers.
6/14/04 The Millenium C(ontinues) - a highly adaptable, cheap, easy to work Millenium Bypass
4/13/04 Cheap - and good - polarity protection
3/14/04 Schematics of the Ludwig Phase II Synthesizer
2/14/04 Applications of an audio Current Controlled Amplifier. Getting a disciplined gain controlled amplifier opens up a huge number of applications. Here are some to start with. The chips are cheap, and you can do a lot of analog processing. Your imagination is the limit.
10/24/03 Variable Stuttering Pedal. Drew the schematic, simulated it. Should work, but I haven't built one on the breadboard yet. Updated for shunt and series switching options.
10/7/03 Vox again. AC30 cabinet drawing and dimensions.
10/1/03 Some thoughts on effects enclosures and rack mounting.
7/27/03 Great Cheddar distortion. Version 1.6, includes look at the BC. Version 1.5 includes all updates for earlier PCB's.
6/5/03 Panning for fun - theory and applications of a basic panning circuit.
5/3/03 Help me check the layout! The gristle box circuit, on a PCB.
4/6/03 Thanks to Normand Cyr for the new GEO logos!
4/4/03 AC30Sim board set. Stephan Moeller's AC 30 simulator circuit. Now with tone/volume controls,toner patterns, wiring diagrams, and commentary on building the boards. It's ready to build!
3/22/03 Updated - a remote footswitch bypassing system, now includes updated layouts and wiring diagrams. Bypass up to six effects from a remote footswitch. Also bypass them ALL with one footswitch. Relay bypass, CMOS logic, 100% fun. Still being developed - your input is welcome!
2/27/03 A remote footswitch bypassing system, now including draft PCB layouts for review. Bypass up to six effects from a remote footswitch. Also bypass them ALL with one footswitch. Relay bypass, CMOS logic, 100% fun. Still being developed - your input is welcome!
2/3/03 The Roland AG5 Funny Cat - a complete build-it article! Thanks to moosapotamus and Rob Strand, without whom it wouldn't be here.
12/15/02 The Zonk Machine and the Hornby-Skewes Treble Booster - a PCB layout and buildit article.
07/30/02 By request - schematic for the Alembic F-2B tube preamp
07/24/02 A circuit in test - the Low Fidelity Pedal; low fidelity/telephone/noise sound
07/20/02 Updated - The Brass-O-Blaster (a clone of the Maestro Bass Brassmaster). PCB layout with wiring diagram. Updated schematic with GEO PCB reference numbers
07/01/02 Updated - The Technology of Oil Can Delays - we know what oil and where to get it! Thanks Tel-Ray page!
06/15/02 And now for something completely different - Optimizing coil structure for max velocity in coil guns.
06/13/02 Mystery Circuit #2 - what does turning that pot do????
05/22/02 Onboard Ric compressor - dull front view; more interesting back view; here's the magic stuff.
04/21/02 Makin' Octaves again - the Mu-Doubler (tm). A new way to make all the octave you want.
04/16/02 JFET matching - Some real numbers; see what you get.
04/08/02 Updated the Ultimate Flanger with John Hollis' latest fixes - including mods to the old boards and step by step instructions to bring them up to the latest level!
04/04/02 New Circuit Sweeping - What are all those parts?
04/02/02 Updated Spyder article with a pic of my steel stud spyder supply getting prepped for drilling
Updated the Guitar Effects FAQ with Keen's Laws
04/01/02 Updated Circuit Sweepings - the Adjusticator
03/27/02 The JFET Doubler - Screaming Octave, Righteous Distortion, and knob to blend between the two. Updated with component values and tuning instructions.
03/26/02 New Circuit Sweeping - using an LED/LDR to eliminate dual pots in LFO's
03/22/02 Use of Carbon Comp Resistors for Magic Mojo - is the magic real? Come find out.
03/21/02 A Vacuum Tube Wah Pedal - the old Vox circuit rides again! Now with power supply circuit.
03/10/02 Hook it up your way - Jimi In A Box
03/03/02 A proposed user interface for the ASMOP remote footswitching system.
03/02/02 The Dallas Arbiter Trem Face Revealed. A tested and working circuit traced from a real unit, and a PCB layout for making your own, along with how it works. Special thanks to Ed Crozier here in Austin for making original units available for this.
02/09/02 Wrap, wrap, they call it a wrapper...
02/05/02 MOSFET Heresies Again! Make a solid state analog of the Fender tremolo circuit for adding tremolo to an non-tremo amp, or free up a tube for more audio gain.
02/02/02 More and bigger Steel Studs. I found an easy source for heavy (18 gauge) steel framing members for bigger and sturdier boxes. Still cheap, but major sturdy.
01/11/02 Computer controlled Pancakes! The pancake footswitch updated to a self contained, hard-metal bypass switch that can be made for about US$5.00.
01/06/02 Pancake footswitches- make your own sturdy, reliable, good looking footswitches for switching effects
12/08/01 Relays for audio switching. The basics of what goes on inside them.
12/05/01 A PCB layout for the PT2399 delay chip. It's right out of the app note, and I haven't built it, but I think the layout matches the app note.
12/04/01 I'm putting together the PIC powered remote switching system. Here's a PICture of the switch board and the eight-loop bypass board.
11/27/01 ... a DIY stomp switch actuator made from hardware store parts!
11/15/01 Power supplies basics.
11/02/01 Some updates to MOSFET Boosters.
11/01/01 Schematics for a Remote Footswitch Controller and Remote Relay Bypass Board, in the ASMOP Section. Schematics for a PWM LFO based tremolo and phaser, also in ASMOP.
10/28/01 Think digital, live analog. Digital assistants for analog effects - the ASMOP* series. Includes a PCB layout for the any-to-any remote switching matrix controller. (*A Simple Matter Of Programming)
10/26/01 Complete layout, parts list, wiring diagram and technical commentary for John Hollis' Ultimate Flanger;
10/24/01 Improved JFET Matcher for JFET phasers.
10/21/01 Updated Omnidrive layout;
10/15/01 Parts list and wiring diagram - John Hollis' Flatline Compressor
10/14/01 Updated John Hollis' Easyvibe, Zombie Chorus; extended MOSFET Boosters article
10/07/01 Updated layout for John Hollis' Ring Frobnicator tremolo/ring modulator.
10/06/01 MOSFET Boosters, Chapter 1. How to design your own MOSFET boosters to meet your own needs.
10/02/01 Remote relay effects switching
9/30/01 Full layout/wiring/parts list for John Hollis' Easyvibe.
9/20/01 Full layout/wiring article for John Hollis' Omnidrive; Layout and building article for John Hollis' Titan Boost/Octave. New techie article - When Good Opamps Go Bad. Also updated "designing tube output transformers" in tube tech pages.
9/08/01 Four new effects layouts - the Omnidrive, Phantom Wah, and Easyvibe circuits as designed by John Hollis, and the BrassBlaster, a clone of the original Bass Brassmaster.
9/01/01 Guest Article - Maarten de Huu's "Construction of Wah Pedals" - make your own foot rocker.
8/19/01 Baa-baa Fuzz Boost, a clone of the Bee Baa
8/03/01 The Steel Stud Enclosure revisited. I took some pictures of folding up a $0.25 enclosure box from steel framing material.
7/20/01 A simple remote bypass box. Put your pedals and the bypass box back by your amp and run a remote switch controller up to your area of the stage. Also a mini, guitar mountable remote switching control. Parts One and Two - design and some PCB layouts.
7/7/01 Mod your Mu-Amp/Minibooster- simple mod for higher gain and lower output impedance.
4/17/01 The $0.25 effect enclosure
4/17/01 PCB layout for Doug Hammond's "Sweet Thing"
4/12/01 PCB layout for Doug Hammond's "Sweet 16"
3/16/01 Vibra-Matic, an add-on effect for the EAN Tremolo
3/9/01 A PCB layout for Aron Nelson's Shaka Express
3/2/01 Note Processing for guitar effects.
2/18/01 A DC protection circuit (OK, three of them...) for solid state amplifers. Save your speakers!
2/12/01 Another treble/bass booster, the Apollo Treble-Bass Booster, provided by Ron Neeley II. Also, see the correction on the EH Axis distortion.
2/09/01 Schematics; the EH Axis / Guild Foxey Lady two-knob version, and the Orange Treble/Bass Booster. Thanks Angelo Marruzzi!
1/27/01 The Sing-Wah, a voice-emulating sequenced wah that jumps from vowel sound to vowel sound either in sequence or at random.
01/13/01 A Wah Sequencer; provides left-right, right-left, and random selection