1. I recently borrowed a single channel microphone preamp made by Applied Research and Technology, the "Tube MP
Studio", selling for less than $100. I was intrigued since vacuum tubes are a bad match for microphones without using an input transformer, and
I couldn't imagine transformers in a unit that cheap. It is in a black steel case with a small grill on the front so you can see the glowing tube. The
input XLR has no lock on it, the output does. I opened it up and it has 2 IC's, 9 transistors and one tube. The manual only mentions it has a hand selected
12AX7 dual triode tube. There is no schematic. Only 5 of the 9 pins are connected so they may be using only one side. Apparently a TL072 dual FET opamp
is used for the balanced mike in and the tube is used in the output stage. I measured the noise performance and compared it with my own low noise design,
for various source resistances. Here are the noise levels in microvolts at max gain, A weighted, referred to the input (i.e. output noise divided by
the gain) with my unit's values in parenthesis: 0 ohms .39 (.047), 90 ohms .4 (.1), 200 ohms .43 (.13), 1 kohms .57 (.3). Clearly the FET input has
medium voltage noise and low current noise and performs better at high source resistances, for ribbon and dynamic mikes it would be a poor choice. For
condenser mikes it would work fine since the impedance conversion is in the microphone. The output stage has a low level 60 Hz buzz, probably due to
the leakage from the AC filaments (it runs on an AC output wallwart). It has phantom power, meter, phase reversal, a peak clipping indicator and a limiter.
All in all a good value, but could be improved by getting rid of the tube!. There is no label as to origin, but the wallwart says Made in China.
2. Thomas G. Stockham, Jr., a pioneer in digital recording, died on January 6 in Salt Lake City. He first caught the
attention of the public with the release by RCA of digitally remastered Caruso recordings. His company, Soundstream, sold 16 of its professional digital
editing systems for around $160,000 each before it merged with Digital Recording Corporation. He was one of the six technical experts on the Watergate
tape made in Nixon's office.
3. A Manchester NH record store, The Music Connection, is profiled in the Union Leader. The owner started the store
in 1957 with the intention of selling off his own 15,000 records, now he has 65,000 LPs plus 30,000 45s and 1,500 78s. The wide ranging inventory, mostly
rock and country albums, has helped him to thrive in an era of CDs and MP3s. "The average age of my customers is 21. There are a lot of teenagers
who come in collecting vinyl. It always amazes me--I'll get a 17-, 18-year-old kid who comes in wanting jazz (records). And they know what they want,
too." Although wanting to sell the business, he never plans to retire. "I do enjoy my work here. If you don't enjoy your business, you're
in the wrong business." 12Ja04
President, Boston Audio Society