The Valve Wizard

Engineering mojo since 2005. Last updated: 13 January 2023; Sound Card Interface updated

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10 December 2019:
Engineer's Thumb updated.

17 September 2017:
Universal amplifier PCBs for sale; make a whole guitar amp 'lego style'. No more pesky turret board!

15 November 2013: I've been getting a lot of mail about my power supplies book. I'm sorry to say I permanently removed it from print. It contained too many mistakes and typos, and it didn't match the style of my preamp books. Do not email me asking if I have spare copies or PDFs; your email will be ignored. Fortunately, all the best material from the power supply book can now be found in the final chapter of my hi-fi preamps book!

Interested in making your own ribbon microphones?
Visit: DIY Audio Components

Website Introduction
Welcome to the wonderful world of valve amps! If you're here then you're probably thinking about tinkering inside one. Building your own guitar amp is a rewarding pastime, but learning how to do it can be time consuming and frustrating sometimes. It is relatively easy to find introductory information on how to design simple amplifier stages, and it is also fairly easy to find extremely advanced information on complex circuit design, and nearly all of it is intended only for hifi! This website aims to fill the gap between the two extremes. I have also tried to remove unnecessary maths and leave only the essential formulae and rules of thumb. This should make the design process quicker and less confusing, leaving more time for the actual building. However, this site assumes that you know some basic principles already, like Ohm's law, roughly how a valve works, etc. If you don't know these things yet then I recommend you read some introductory electronics material. Even so, I have done my best to write these tutorials cook-book style so anyone can follow along without actually knowing how it works- but it certainly helps to understand first. Although aimed specifically at designing guitar amplifiers, principles of hi-fi have been included here so that audiophiles may find something of use too, and guitarists should be able to learn some of the science behind the mojo.

Building and modifying amplifiers is DANGEROUS (like most fun things). Valve amplifiers invariably contain both high voltages and high currents, capable of killing you. I provide the information on this site free of charge, and it is up to you to exercise caution and common sense at all times to avoid electrocuting yourself, and make your amplifiers safe to use. I am not responsible for your negligence. Building valve amplifiers is also more addictive than nicotine; you have been warned.

This site is always under construction.

Contact: Be sure to put 'valve' or 'tube' in the subject title or your message may be blocked.
Suggestions, comments, criticisms welcome. Donations gratefully received through