Listed in alphabetical order:
Acoustica.org.uk is basically a scratch-pad, a useful-pot to keep things in. It's mostly about audio engineering with a DIY flavour, salted with other odd things found interesting.
Great website featuring interesting articles I find entertaining
Countless schematics and service manuals for products of many different brands. The perfect resource for anybody repairing equipment. Jan Dupont maintains this great resource free of charge.
Half of Andrea's webiste is advertising, but there is some good information in between. The link goes straight to a more useful page.
This great website and forum offers reviews of audio gear that is based on real measurements instead of purely subjective statements and therefore highly recommended to anybody looking for solid data.
As the name implies, this website is about building audio amplifiers. There are many designs available. Most designs are pretty basic, typical DIY projects. You need to register in order to view schematics.
Countless clever circuit ideas
I like Bob's book very much. He is also very active on the DIY Audio forums.
Edmond Stuart's website. Make sure to read about his impressive PGP (Pretty Good Power Amp) project.
A great place where experienced audio enthusiasts share their ideas and knowledge.
Douglas Self is a highly popular audio specialist has published many books about audio amplifier design and other audio relates topics. I own two of his books and find them a good read. However, in my opinion, Douglas is a bit quick to dismiss ideas and concepts. Many of the concepts he dismissed in his books were made to work well by other designers. Douglas promotes his blameless amplifier, which is the most basic audio amplifier that performs reasonably well.
Construction drawings for loudspeakers (commercial) and some interesting basics about loudspeaker design.
Bauvorschläge für Lautspecher (kommerziell) und ein paar interessante Grundlagen zum Lausprecherbau.
Chris Russel's website
Impressive loudspeaker projects, especially horn loaded ones
Jon Snell is a valve specialist. He builds and repairs valve amplifiers and offers spare parts for valve amplifiers. He is also active on the DIY Audio forum.
Small website of a DIYer showing some DIY equipment. Not particularly useful, but I like the photographs of the beautiful and unusual equipment that is showcased.
Pavel is known as "PMA" on DIY Audio, where I enjoy him sharing his ideas, schematics and advise. He also has his own website, where he presents his projects.
Samuel Groner is well respected in the audio community and has written some very interesting articles. His website also features links to further interesting websites.
Features some articles about audio and many other technical articles.
The HiFi Engine library has images, specifications and reviews for thousands of audio components, along with owners manuals, service manuals, schematics and product catalogues for amplifiers, pre-amps, power amps, tuners, tape decks, cd players etc.
Thanks to the many visitors who have scanned documents and donated images to the gallery.
Service only after registration (free of charge)
Electromagnetic Compatibility Consulting and Training
Good electromagnetic design is relevant to all kinds of electronics and audio. I have learned a lot about EMC from studying technical articles written by Henry Ott and highly recommend this resource for education.
Welcome to over 500 posts and to over 50 articles on amplifiers, tube-based preamps, crossovers, headphone amplifiers, single-ended amplifiers, push-pull amplifiers, Circlotron circuit design, hybrid amplifiers, cascode circuits, White cathode followers, grounded-cathode amplifiers, tube series regulators and shunt regulators, the Aikido amplifier, tranformer coupling, DACs and tubes - and hundreds of vacuum tube circuits that use 6SN7s to 300Bs, all explained in careful detail.
Website by DIY Audio member Keantoken. I like his power supply rail filter very much.
Paul Kemble's website features many interesting articles and is well worth a visit.
Jan Didden's website
Jan Didden's magazine. Haven't read it yet, but believe it is excellent
Pierre has investigated a phenomenon that is not discussed often, but seems to be relevant: Memory distortion. I highly recommend studying his work.
Marc has a very helpful website featuring two e-books: One about radio telemetry systems and another about power quality issues and cures. The website also features many technical and non-technical articles worth reading. Highly recommended!
Martin J. King maintains a website specialized on quarter wavelength loudspeaker design. I know only some basics about loudspeaker design and this is way beyond me, but I believe this website is a very useful resource for anybody getting into the specialized field of quarter wavelength design.
Haven't read much of this, but it seems interesting
Excellent website about building loudspeakers, featuring Thiele and Small parameters of more than 2000 drivers of more than 160 manufacturers. The authors also developed and maintains the software "BassCAD" for designing loudspeaker chassis, which I like very much.
Excellente website zum Thema Lautsprecher. Hier gibt es Thiele und Small Parameter von über 2000 Treibern von über 160 Herstellern. Ich schätze zudem die software "BassCAD" zum Design von Lautspechergehäusen, welche der Autor entwickelt hat und weiterhin pflegt.
I'm neither into tube amplifiers, nor do I speak Japanese, but somehow I find this website deserves attention. Shinichi-Kamijo builds tube amplifiers and has a website where the projects are documented.
New discovery for me in year 2021: A HiFi / High End audio magazine featuring news, equipment reviews, galleries and much more. I find this very entertaining to read.
Suzy's blog is about audio, wooden boat building, computers, electronics, lugged steel bicycle frames and other typical girls things. Suzy Impresses with outstanding craftsmanship in all of her projects. I find her blog entertaining and worthwhile reading.
Seems like another Edmond Stuart website
Nice website offering some helpful articles about electronics and audio design. Also features some articles about programming, many other topics and a photo gallery. Somewhat reminds me of my own website.
TheSlowDIYer is a quite entertaining website about the author's DIY audio projects.
Online HiFi review
Free and proudly independent (no-advertising) since 1996
This websoite looks like a helpful resource for designing transmission line loudspeakers. Probably a good compliment to the quarter wavelength loudspeaker design website.
Collection of his e-books, resources for CFAs, references and regulators
Some interesting projects, articles and resources. New addition to this list. I haven't read much of this yet.
Listed without any order:
Spice models from Bob Cordell are well respected in the audio community. I use them almost exclusively for simulating my designs.
This small wiki describes the best setup to simulate FFT with LTSpice
This guide has helped me a lot identifying and solving any convergence issues without resorting to hacks.
Some of this may be very helpful.
Sometimes online calculators may be useful for a quick estimation. Here are some calculators I use often. Listed without any order.
This calculator from Okawa Electric Design is excellent for checking whether a L-C low pass filter design is good or not. They offer further calculators I haven'tried yet.
This is the most useful calculator for toriod inductors I have seen so far.
Sengspiel Audio offers a useful calculator for Decibel values.
Easily calculate the resistor value of any color or digit coded resistor. This is especially useful in case the resistance cannot be measured.
The best geometric calculators I found on the web including geometric forms I have never heard of before.
This collection of calculators by AJ Design is mostly for physics and economy.