Useful Links.
AUDIO RECOURCES:
AUDIO tutorials, questions and documentation on sound recording, studio technology, recording technology and sound engineering by the late Eberhard Sengpiel. The site is managed by his son Alexander Sengpiel.
http://www.sengpielaudio.com/Calculations03.htm. HUNDREDS of VERY USEFUL Audio and other calculators with explanations in German & English.
http://www.voxshowroom.com Lots of Vox amplifier, guitar and organ information. Very useful.
Classic Audio Products, Inc (capi-gear). API info, clone parts etc. If you are interested in API gear, take a look.

AUDIO FORUMS:
Groupdiy.com: https://groupdiy.com
Gearslutz.com: https://www.gearslutz.com
Recording.org: http://recording.org
Thestringnetwork.com: http://www.thestringnetwork.com
3D Audio Bulletin Board: http://www.3daudioinc.com/3db/forum.php
Badcaps.net All about caps, not just for audio: http://www.badcaps.net

TECHWORLD:
TECBRIDGE CIRCUITS. QUALITY PCB 's at the lowest possible cost - Single Sided - PTH - Multilayer.
SUGRU. Wicked glue that sets like rubber. Many different uses and colours. Great for fixing and making things.
THERMOMORPH. Mouldable plastic pellets. Heat to 60 deg C in water to use. Sets very hard.

SOFTWARE:
LIBRE OFFICE. FREE Alternative to Microsoft Office BUT MUCH BETTER.
VISUAL ANALYSER. FREE software analyser for PC.
Oscilloscope, Spectrum Analyzer, Wave-form generator, Frequency meter, Volt meter, Filtering
And MUCH MORE !
ELECTRONICS ASSISTANT. Free Software & many useful calculators etc.
EVERY CIRCUIT. Create, simulate, share, and explore electronic circuits! For Apple, Android & Chrome.