Constant Current for Tube Heaters. Extend the Life of Your Amplifier’s Vacuum Tubes

In this article, Bill Reeve explains how to drive tube heaters with a constant current to lengthen the life of your vacuum tubes. As he explains, obviously, the best way to extend your amplifier’s vacuum tube life is to never turn it on. Some would say that the second best thing you can do is to never turn it off. The third and fourth options may be to gently turn on the tube heaters and not leave the B+ voltage on when the heater voltages are off. This article was originally published in audioXpress, May 2014.

From March to August 2014, in its Sound Control column dedicated to acoustics, Richard Honeycutt reviewed and wrote a series of articles on the evolution of predictive acoustics and acoustical modeling software, including a review of some of the available tools. This third article in the series discusses CATT-Acoustic, a software for room acoustics prediction, auralization, studio stereo, and surround reverberation, and one of the leading modeling programs for architectural acoustics. This article was originally published in audioXpress, May 2014.

The 7” RS180P-8 Reference Series midwoofer from Dayton Audio uses a nice six-spoke cast-aluminum frame with narrow 10-mm wide spokes to minimize reflections back into the cone. The cone assembly is composed of a three-part lightweight paper cone that combines Kevlar and glass fiber with the paper slurry. Cosmetically speaking, this is very good looking driver. This article was originally published in Voice Coil, May 2014.

The BMS 4507ND is a unique transducer that uses a neodymium coaxial compression driver to drive a planar waveguide intended for use in line arrays. BMS Speakers patented the two-way compression driver technology in 1997. This month’s Test Bench subject, the 6.5” 4507ND features a 300-Hz to 22-kHz bandwidth (6 to 22 kHz for the tweeter and 400 Hz to 6.3 kHz for the midrange). The rectangular planar waveguide is optimized for 0° to 15° vertical dispersion and up to 120° in the horizontal plane. This article was originally published in Voice Coil, May 2014.