Build a tube Mic Pre: Build Your Own Two Channel Vacuum Tube Mic Preamp! | Tape Op Magazine | Longform candid interviews with music producers and audio engineers covering mixing, mastering, recording
XFMR DIY Projects: Magnecord PT6-J Made into Preamp plus Vari-Mu Tube Compressor / Limiter "Pre+Limiter"
A Simple One-Tube Compressor Circuit c.1953 – Preservation Sound
Vacuum Pump 12V Mini Diaphragm Air Compressor with Silicone Tube : Amazon.co.uk: DIY & Tools