Dave Royer and I are big fans of the Raytheon 5840W vacuum tube. It is an integral part of the design of Royer R-122V and SF-24V vacuum tube ribbon microphones, our highest-level mics. Many other companies use Raytheon 5840Ws in their microphones.
Do-it-yourselfers like this tube for a variety of projects such as microphones, pedals, and numerous audiophile applications. Several years ago, Tape Op magazine published an article David Royer wrote about upgrading inexpensive Chinese condenser mics. His choice of tube was the venerable 5840.
This tube is a pentode and can be wired as a triode with excellent results. There are numerous projects on the internet that call for this little workhorse.
We purchased all the good 5840Ws we could find in Royer’s early days. We’ll probably never use all of them, so we’re making them available on a one-by-one basis.
These are prime mil-spec Raytheon tubes that are pre-sorted and fully guaranteed. A data sheet is provided with each tube.