Why Tubes?

If you’re not an electric guitar player or if you’re just starting out, you might ask why anyone would build anything with tubes. Aren’t vacuum tubes an obsolete technology? Well, yes and no. While tubes are no longer the technology of choice in the computer industry, they are very much alive and well when it comes to modern high-end guitar amplification. It is because of the electric guitar amp that vacuum tubes are still being manufactured today. Visit your local guitar store and take a peek at the rear side of the amps, you’ll most likely see a variety of glass tubes projecting from the amp chassis.

Guitar amps with tubes are currently front and center in the high-end market because many guitar players find their sound characteristics to be superior to solid-state amps (i.e. amps with transistors as the main active electronic devices). Modern mass produced tube amps use printed circuit boards to connect components, but at the extreme high-end there are “boutique” amp builders who hand wire connections from point-to-point and select high quality components. Point-to-point wiring is how vintage guitar amps from the 1950’s and 60’s were wired and it’s a technique that allows for easy maintenance and circuit modification.

DIY and the Boutique Amp Builder

Boutique amp builders are individuals or small companies who build a relatively small number of amps each year with an emphasis on quality and attention to detail. Boutique amps are usually priced in the thousands of dollars, because they require a lot more time and skill to produce. The builders will often customize circuit designs to satisfy the different tastes and styles of individual guitarists. Most boutique amp builders at one time started out as electronics hobbyists who thought it would be fun to modify or build their own tube amp. The internet continues to make it easier to find books and parts to help you build your own boutique quality guitar amp.

Suggestions for a First Build

The quickest way to get acquainted with the parts and standard layout techniques used in tube amp building is to build an amp kit. Most kits come with a pre-punched chassis, parts and instructions to assist you in building it.

If you’re interested in more of a challenge than building a kit, classic tube amp schematics are easy to find on-line and their patents are likely to be long since expired. Find a Fender schematic and its related layout drawing and start making a parts list. Most of the boutique amps being made today are cloned vintage Fender and Marshall amps or at least heavily influenced by their circuits. There are also many books on the subject of tube amp circuit theory, design and building that you can read to help make your first build of boutique quality.

Circuit Schematic Resource Links

http://www.schematicheaven.com

http://www.fender.com/support/amplifier_schematics.php

http://www.freeinfosociety.com/electronics/schempage.php

http://www.schematics.ca

http://www.drtube.com/guitamp.htm

Happy building! □

Kurt Prange (BSEE) is the Sales Engineer for Amplified Parts in Tempe, AZ. Kurt began playing guitar at the age of nine in Kalamazoo, MI. He is a guitar DIY’er and tube amp designer who enjoys helping other musicians along in the endless pursuit of tone.