|Hawes Amplifier Archive
Hot Rod Power Amplifier Experiments
Safety Features. Also beyond this page are safety features, such as foldback circuitry. You'll note that these are stripped-down circuits. They contain no protection against overcurrent or overvoltage operation. A short circuit in the output will quickly destroy such an amplifier. But parts are cheap and servicing is easy. If you will, build and enjoy!
Rock 'n Roll Your Own! If you're both a guitar player and an experimenter, these circuits are what you need. These aren't stage amps, but they'll be just fine for a bedroom practice session. By the way, if you just want a dependable, serviceable amp, but can't play guitar, follow along. Just think of these circuits as “utility power amps.”
Must have a preamp or two. None of the circuits on this page can stand alone. Each circuit needs a power supply and a preamp or two. The preamp circuits are on our preamp page. Make sure that you add an emitter-bypass capacitor to these circuits. Use a 20 μF or larger capacitor (larger caps provide more bass). See...
Battery Discharger. Don't even think of running these amps with two nine-volt batteries. If you try that, call these circuits “battery dischargers.” What? You insist on battery operation? Okay. Use hefty batteries. For example, 12 “D” cells in series.
Mostly Radio Shack Parts. The first schematic is for those who seldom buy parts anywhere but Radio Shack. You can walk in the store and walk out with all the electronics that you need. For the heat sink, sorry to say, you're on your own. Find a hardware store and buy a big chunk of aluminum. Saw the aluminum chunk into two pieces. Paint the aluminum pieces flat black. The paint actually increases the magical powers of the heat sink. No kidding. Slather the transistors with silicon heat sink grease. Bolt each power MOSFET to its own piece of aluminum. Go in peace. Play loud. Sing until you steam up your bedroom or either a girl or the police show up. (If you're a girl rocker, howdy! Beg pardon. If you're a girl cop who plays rock music, cool.)
Most Everything from Radio Shack
Kick Up the Volume
Gain vs. tone. For more gain, increase the size of the resistor RF. For better tone, decrease the size of the same resistor.
Simpler design. Without the need for phase reversal in the preamplifier, the new circuit eliminates one JFET. (You may still use differential JFETs if you please. Just connect the 4.7µF feedback capacitor CF to the non-inverting input.)
Heat Sink Requirement. For the heat sink, follow the suggestions for the other circuits above.
More to come!
1. Daniel Meyer, “Reverb for Your Car,” Popular Electronics 25, no. 2 (1966): 50. ▶Re: This article inspired our optional feedback loop (CF / RF). Thanks to World Radio History for preserving this archival copy of the groundbreaking electronics magazine. Please turn to page 50.
▲ WARNING. This is your project. Your achievement is entirely yours. I assume no responsibility for your success in using methods on these pages. If you fail, the same is true. I neither make nor imply any warranty. I don't guarantee the accuracy or effectiveness of these methods. Parts, skill and assembly methods vary. So will your results. Proceed at your own risk.
▲ WARNING. Electronic projects can pose hazards. Soldering irons can burn you. Chassis paint and solder are poisons. Even with battery projects, wiring mistakes can start fires. If the schematic and description on this page baffle you, this project is too advanced. Try something else. Again, damages, injuries and errors are your responsibility.
♦ CAUTION: UNBUILT DESIGNS. These are unbuilt designs. You might need to refine them before they'll work. The circuits show promise. My point for this page is to share some ideas that might work. If you're an experimenter, the circuits are food for thought. That's the fun of inventing. But if you need something that works the first time and works perfectly, you'd better move on! — The Webmaster
Copyright © 2010 by James T. Hawes. All rights reserved.