0. We will be accepting nominations for officers at the October meeting. That's President, Corresponding Secretary,
Membership Secretary, and Treasurer.
1. "Noise and Moving-Magnet Cartridges" describes a circuit technique that achieves better noise performance
in a phono preamp than has been achieved before. With moving-magnet cartridges, the limitation on the noise at high frequencies is that generated by
the 47 kohm terminating resistor. This is the standard input resistance and cannot be changed. The author replaces it with a 1 megohm resistor and actively
drives the end that would normally be grounded in order to simulate an input resistance of 47 kohm. The inductance of the cartridge shunts the noise
of the 1 meg resistor so it doesn't appear. An improvement of about 3 dB is achieved. The article goes into great technical detail on the noise sources
and their minimization and is highly recommended to phono preamp mavens. Electronics World Oc03.
2. As a followup to last month's item "ASLSP", astronomers say they have heard the sound of a black hole
singing. What it is singing, and perhaps has been singing for more than two billion years is B flat a B flat 57 octaves below middle C. It appears
as pressure waves through a hot thin gas that fills the Perseus cluster of galaxies 250 million light-years distant. The waves are 30,000 light years
across and have a period of oscillation of 10 million years. "It's the longest lasting symphony we know of," said Dr. Bruce Margon, an astronomer
at the Space Telescope Science Institute. NYT 16Se03
3. In "News of the Sections" in the AES Journal, there is an unusually long writeup ( 2-1/2 pages) of a
meeting of the Pacific Northwest Section, reminiscent of the detail and color of the better BASS writeups (I applaud this since the bulk of the journal
is of little interest to me). It is about Greg Mackie and his audio companies ( Tapco, Audio
Control, Mackie Designs) in the Pacific Northwest. One illustration: they liked the feel of
the Alps pots, but couldn't afford the minimum order requirement, so they used cheap CTS pots. To get the viscous feel they tried STP, silicone heat
sink grease, Crisco, and even raisin juice on the shaft. Finally someone came up with a compound that worked. Using it meant that they had to disasemble
and reassemble each pot . Sometimes the compound got on the carbon element, causing clicks. Finally they hit on the idea of laying a bead of the compound
around the shaft-bushing junction and heating the pot in an oven. Capillary action did the rest. Years later they discovered that the goo glued the
polystyrene knobs to the shaft, making service a challenge. AESJ JL/AU03
David Hadaway
President, Boston Audio Society
email:
dhad000@yahoo.com
|