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"Feel the Gain" Part 2: 12ax7 gain stage
Are you strapped in? Let’s look at a common 12ax7 tube gain stage. This is found in many guitar amp circuits. Let’s continue where we left off, as the signal path from the previous section enters pin 2 (the control grid) of the V1A 12ax7 tube. Looking at the image to the left, the role of the 12ax7 type vacuum tube in this circuit is to take your tiny signal going into pin 2 and have it come out of pin 1 much much much bigger. Much bigger. Bigger than you think. 100 times big
Bob Judge
9 hours ago2 min read


"Feel the Gain" Part 1: Guitar Input
Let’s start at the beginning. Genesis 1:1, the Big Bang, the giant chicken egg. Your instrument’s signal will need to enter the amp circuit. The most popular method is the 1/4” jack. One simply acquires or makes a 1/4” male to 1/4” male instrument cable, plugs one end into their guitar jack and the other end into the jack on our amplifier. “Ahem, excuse me, Author. Duh, I know that! Now what?” Let’s take a look at a Fender Deluxe Reverb input. The guitar signal enters the fir
Bob Judge
Oct 152 min read


About the Blog
About once per week since 2021, I’ve been asked if I’m looking to hire an intern or apprentice. I never was and I’m still not but I sometimes bring them on anyway. The intern has always been a young guitarist looking to learn and possibly start a career as an amp tech. When a repair comes in the first question is, “What do you think is wrong with it?” And I respond, “I have no idea!” And I don’t. I could guess but that would put me in the same camp as those hundreds of intern
Bob Judge
Oct 142 min read
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