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9/4/18 CMOS circuits and theory for generating octaves up and down from guitar
2/19/17 More repair books for Thomas Organ Vox amplifiers are coming on line at http://www.thomas-vox-repair.com/ The lineup now includes: 
  • The Vox Owner's Safety Net
  • Vox Footswitches
  • V117 Sovereign Repair Supplement
  • V1181 Westminister Repair Supplement

The V1141 Beatle Repair Supplement and V1121/V1151 Buckingham/Viscount supplements are up next.

12/24/16 It took a lot longer than I intended, but the Vox Owner's Safety Net is now available on line at The Book Patch (thebookpatch.com), as is the Thomas Organ Vox Footswitches Manual. See: 
The Book Patch Bookstore: Vox Books
The Safety Net is an overview of the entire Thomas Organ Vox line before the Series 90 amps, and covers the solid state amps from the 1960s. The book is a technical repair manual on how they work, and how to fix them in general. It's far more than a simple set of schematics for the amps. I hope this will help Vox owners convince more techs to do repairs and keep these amps running.

The Safety Net is an overview. For people needing more detailed info on a specific amp model, there is a series of Repair Supplements, one per model number on the way. These are being written in the order of my best guess about what model was most popular - and hence most needed today. 

The Footswitches manual is a collection of all the footswitches schematics and the technical insights on how to distinguish which footswitch went with which amplifier, how to fix the lights, and how to add/replace lights when needed. Also included are mechanical drawings on some ways to make new footswitch assemblies from scratch for an amp that's just missing them.

Fixed R24/R25 part number mistake in Ultraflanger article
Repair boards for Thomas Vox checked out! It's now possible to completely rebuild a Beatle/Guardsman/Buckingham/Viscount/Cambridge/Berkeley II...
A tube amp B+ reduction circuit; note that this is all HAZARDOUS AC POWER WIRING.
2/22/15 A tube amp biasing and protection circuit; front panel and operation

Work in progress: Preliminary board documentation for Vox Cambridge/Berkeley/Pacemaker/Pathfinder
11/9/14 Work in progress: Preliminary documentation for Vox guitars' onboard effects
7/29/14 Work in progress: Preliminary board documentation for Vox Beatle/Guardsman/etc repair parts.
6/9/14 New Vox Stuff. How to fix the blasted power switch and how to make a replacement driver transformer.
7/18/13 Experimental transformer salvaging stuff
6/3/2013 Updated UVICS-3 and Son of UVICS project file
5/13/2013 An onboard preamp for guitars
12/11/2012 Using PNP transistors to switch power to FX circuits.
10/16/2012 Updated documentation for the second run of Ludwig Phase II PCBs.
5/22/2012 I got asked again, and it prompted me to write down why I work for Visual Sound.
5/1/2012 Updated the Ludwig Phase II clone article.
4/29/12 Return of More MOSFET Follies
3/27/12 A tube amp rectifier current clamp. This inserts between your rectifiers and first filter cap. It limits the surge current into the filter cap to safe values at power on and coming out of standby to soften the surge of current. Although this is not exactly the same as a tube rectifier does, it's quite similar in results. 
3/27/12 A sketch of the dimensions of the JMI AC50 amplifier head updated 3/27 with more details and some building/woodworking instructions and comments
11/1/11 Someone sent another request. OK, here's how to fake your own Vox Grill Cloth, in detail. It's a huge amount of work, but you may like it. 
10/31/11 I got a request for how to do this. Here's how to make your own Vox Grille Cloth. Actually, it's only how to make the tool to hold the stuff in place so you can make your own. The actual making of it is a long, involved process. I buy my grille cloth.
9/27/11 Resurrecting a dead Thomas Vox Beatle from the ground up.
9/26/11 Updated the Ludwig Phase II clone article; updated parts list and drilling instructions, as well as spread traces for easier toner transfer. 
8/16/11 Here's the updated schemo of the whole Ludwig Phase II. I took it down a while back. This one has been corrected.
8/10-11/11 Original buildit article cloning the Ludwig Phase II has been completely updated on 9/26/11, which see.
8/2/11 Tech review of the Ludwig Phase II
7/26/11 Son of UVICS 8-)
7/18/11 UVICS-3 updated with info from a test build
7/14/11 Sizes and hole locations for PCBs to fit in Crybaby shells.
7/2/11 UVICS: Univibe in a Crybaby Shell (removed for updated version see UVICS-3
3/6/11 A new picture of a Vintage Voltage Adapter built for a Fender Deluxe.
12/12/10 Replacing Thomas Vox amplifier transistors and electrolytic capacitors
11/20/10 New Technology of... article; the Technology of Boss and Ibanez Bypassing. This includes what to remove and short to add an external bypass box, and how to add an INTERNAL true bypass relay to let you have a true bypassed pedal, with the original LED working, no external bypass box, and no butchery of the pedal enclosure.
10/4/10 Some updates for the forty-five year old Thomas Vox amps... I did a new board set that replaces the entire preamp circuits and eliminated much of the internal wiring. 
08/09/10 11/20/10 Adding an internal relay to Boss and Ibanez pedals using only the existing switch and latch circuits has been incorporated into the technology of Boss and Ibanez bypassing.
08/03/10 I had occasion to do a fresh bit of photo based circuit tracing, so I wrote up a little photo essay on how you might use this technique. Tracing a PCB
06/26/10 I had to mess with the Q&D oscillator, and in the meantime I updated it for my bench use. You might like the Fake Guitar Oscillator for your bench too. 
3/08/10 Dinking with some Neovibe derivative layouts. Here's a comparison of the boards for three different versions. The biggest is a "stone axe" style, biggest pads, traces and spaces I could stand to do. The middle one is similar to the existing Neovibe layout, and the little one is a drop in fit for the Crybaby shell, with matching hole locations and wires out. Note that there may be some trace/routing errors in these, so don't use them for making your own yet. 8-)
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. 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?

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' EasyvibeZombie 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 of a number of user settable wah positions. 
01/10/01 The Polarity Reverser.
10/21/00 Updated LFO Generation section with interfacing information for the Digital LFO generators.
10/12/00 Updated LFO generation section with stairstep and pseudo-sine circuits; new area - Circuit Sweepings - which is bits and pieces of circuits to include in effects. See the +9V to -9V converter and the +9V to +33V converter circuits.
10/6/00   The Psuedo-random LFO installment 1
From Stan Cotey -  Brian May's treble booster?, purported to be the Real Thing. Thanks, Stan! 
9/02/00 New "Tech of..." article - the Technology of Envelope Controlled Filters by Mark Hammer. 
8/27/00 Foolin' with FETs - a techie walk through some two-JFET circuits 
8/18/00 How to select Fuzz Face clone transistors with one DMM and two resistors. 
8/10/00 Stomp switches are back. Heavy duty Carling 317's. Includes a free Millenium Bypass PCB with each switch. See the stock list.
8/6/00  Comparison of Dyna-Comp and Ross Compressor schematics.
8/5/00 D&R Compressor PCB's now available - see Stocklist! One board -  either the MXR Dynacomp or Ross Compressor 
Build the Austin Treble Blaster! Same circuit as the old original Dallas Rangemaster from the early 60's. Unique PCB design for easy mounting on its own boost control!  Also - why does your stompbox pop when you hit the bypass button?
7/3/00 Add an Expression Pedal to any effect!
6/30/00 Population diagrams for the Hot Fuzz Pro to make a Hot Fuzz, a two knob Tone Bender, or a Fuzz Face - including parts list.
6/28/00 They're here! PCB's for building the Shaka Brada 3 are back, and the new boards for the Hot Fuzz Pro, which can be a 2 knob Tone Bender, and several variations.
6/14/00 Electronic Switching with the CD4053; an improved Audio Probe;
6/13/00 Millenium 2 Bypass extensions - quiet the inputs of noisy fuzzboxes or do other switching; also the Multi-Vol - select one of six preset volume levels or a rocker volume pedal with a tap of your toe.
6/07/00   Hum-free A/B/Y Guitar Splitter based on GFR's picture. This works great for hum voltages less than a few volts. 
6/06/00 Beginner's time -  How It Works, first installment
5/31/00 Tube Amp Star Grounding - for a hum-free amp.
5/27/00 Point to Point better than PCB's in amps? Not necessarily...
5/22/00 FX soldering block to make FX wiring easy.
5/21/00 Guitar Effects Debugging Page.
5/19/00 The Spyder - a hum-free pedalboard power supply
5/15/00 checked-out toner transfer layout for the Mini Tubes 1 and 2.
5/8/00 PCB layout for Dr. Quack. See the Parts and wiring diagram and the actual size toner transfer pattern.
5/5/00 Fixed  Bluesbreaker layout
5/2/00 PCB layout and toner transfer to build the Guitar Preamp and Vibrato (actually tremolo) from Electronics Australia 1968.
4/28/00 Added Envelope Detector (Module 07) and Voltage Controlled Filter (Module 06) derived from the EH Dr. Q auto-filter to the FXBus 1 Both together gives a Dr.Q style filter, but the functions can both be applied separately - that's why we're making a modular bus! Also, Module 5, a feedback diode clipping stage, Module 8, a Big Muff style tone control, and Module 9, a Big Muff style clipping stage.
4/25/00 Updated FX Bus with a Buffer/Gain/Booster module, a JFET Mu-Amp layout, and a Tube Amp Style Tone Control module. 
4/19/00 The FX Bus
4/15/00 Free download - PCB layout for the Mini-Tubes 2 Preamp You can also build a Mini-Tubes I on the same layout!!
3/16/00 Soft Power On Tester for Amps
3/14/00 Making Repro Vox Dust Covers
2/18/00 Building Repro Vox cabinets
1/28/00 Heresy on the hoof! Uses for MOSFETs in tube amps - first installment.
1/18/00 A programmable FX switching system  
1/16/00 Updated How to Design Output Transformers 
1/14/00 A guest article by effects experimenter, Scott Swartz; the Screamer Octave
12/20/99 All the files at GEO with my original content have been digitally watermarked and registered with the US Copyright Office, as will all updates.   In addition to proof of ownership and date, this enables specific legal remedies for infringement. I do apologize for having to do this, folks, but I'm tired of my stuff appearing under someone else's name at other sites and then getting libeled if I complain. There is now no question about who generated what content. Read my copyright statement.
12/7/99   Crackle Painted boxes, Austin Treble Blaster board, new Millenium 2 board.
12/5/99 SAD 1024 pinout and technical information
11/14/99 Advanced polarity protection with MOSFETs
11/09/99 PCB layout and toner pattern for the Bluesbreaker schematic at J.D. Sleep's web site. Download, print and etch. Copyright permission granted for individual, non-commercial use in building personal guitar effects. Also - the Guitar Effects FAQ has been updated with information on effects order in pedalboards, an update to fixing broken pedals, and other minor changes.
11/04/99 the Juggler, a foot-stompable effects order reverser. 
11/01/99 the Technology of Oil Can Delays - how those Morely echo effects worked.
10/18/99 Effects Prototyping Techniques - Lotsa ways to build a circuit!
10/13/99 Test layouts for two versions of seven band graphic EQ - one with garden variety opamps and transistors, one with a graphics-EQ chip.
10/8/99 Simple, Easy Parametric and Graphic EQs
10/4/99  A quick and dirty audio test oscillator for testing.
10/3/99 Dead Bug prototyping - the fastest and easiest way to make reliable circuits for simple effects.
9/19/99 Drill FX boxes reliably - Paper Templates; Use plastic boxes without hum - Using Plastic Boxes
Replace the pesky 4739 and CLM6000 in Craig Anderton's EPFM and GP projects.
9/4/99 The Technology of the Wah Pedal update; why- it sounds a bit like a voice and -how- it could sound more like one.
8/31/99 The Secret Life of Pots
8/27/99 The Technology of the Wah Pedal  
8/10/99 Vintage AC adapter
7/29/99 - [Aron Nelson's Minibooster 2 (pdf)]  
- [Shaka Brada 3 (pdf)
- [Rocket Distortion (pdf)
- Bulletproof your Solid State Thomas Vox Amplifier
Always... The only way to get real tube sound in a stomp box ;-)


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