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Articles by R.G. Keen

Make a Mic Muter

November 11, 2008
Build a mat that switches your mic on and off when you step on it.
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Troubleshooting Tube Amps

October 13, 2008
Although I’ve never repaired amps for a living, I have repaired a lot of amps through the years. I get a lot of questions e-mailed to me from amp-repair novices
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The Immortal Amp Mods, Pt. 4

September 9, 2008
R.G. discusses the importance of paying attention to your amp''s filter capacitors.
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The Immortal Amp Mods, Pt. 3

August 15, 2008
Preparing your amp for unexpected power surges and electrical spikes.
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The Immortal Amp Mods - Pt. 2

July 10, 2008
The first Immortal Amp Mod addressed a weakness in the tubes. Our second installment will help prevent another way tubes can damage the amp. Protect your transformers with fuses I’ve
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The Immortal Amplifier Mod

June 10, 2008
A well-made tube amp can last a long time, but there are a few things that can make them uneconomical to fix, as well as unreliable. If you were
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The Life and Death of an Electrolytic Cap

May 12, 2008
How electrolytic caps are born, and why they die
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Are You Listening With Your Eyes?

April 9, 2008
Some people have the idea that controls on a new effect should always be set to the midpoint or 12:00 on a hypothetical clock. I’ve heard a variety of answers
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The Ins and Outs of Layout

March 11, 2008
A lot of boutique pedal and amp makers are re-discovering that where you place parts with respect to each other makes a big tonal difference. If you’re an effects builder,
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The ’59-’63 Fender Concert Vibrato

February 8, 2008
Over the years, Fender has used two different effects that are labeled “vibrato.” One simply modulates the loudness of the signal. The other is more interesting to me; it modulates
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Tube Amp Tune-Up

January 9, 2008
Just like your car will eventually sputter to a halt and die if you never change the oil, your amp will eventually develop problems if you neglect to devote
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Exploring Tone Controls

December 11, 2007
Practically every piece of musical electronics we use has one or more tone controls. We all use them intuitively, but let’s look closer. To make frequency selective networks, we
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Should You Bypass True Bypass - Again?

November 9, 2007
There aren’t many things worse than stepping out on stage in front of a crowd and being met with silence from your rig, but there’s a growing risk of that
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Diode Stew

October 10, 2007
This month, I felt like taking a little dive into circuits for you solder-breathers out there. There are two main ways that diode clippers work, and there are subtle
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Why is a Good Amp Tech So Hard to Find?

September 10, 2007
--> There seem to be two major questions about amp repair: why is amp repair so expensive that we don’t dare have an amp break? And why are good
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Adjustable Clipping in VOX Amps

August 8, 2007
Delving into classic amp circuitry.
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True Confessions: I Like Thomas Organ Vox Amps

July 11, 2007
The ups and downs of the Thomas Organ Vox Amps of the 1960''s.
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The Secret World of Amp Caps

June 12, 2007
If you keep your amp long enough, one day it will slowly start sounding a little off.
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JFET Switching

May 14, 2007
Boss and Ibanez pedals universally use JFETs for bypass switching, and the operation of the circuit is a little mysterious until you have dug all the way to the bottom
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Tube Matching - Needed or Not?

April 12, 2007
Do you need matched output tubes? Is it worth the extra bucks? Are unmatched tubes just as good? There are at least three major things to match in output
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