Custom Microphone Preamplifier "SS"

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One of the first designs I tried at Transient Sound, this is a pair of all-solid-state (hence, "SS") channels, with capacitor-coupled inputs. I primarily wanted to hear how the (now discontinued) Analog Devices SSM2017 "self-contained" audio preamplifier IC performed. The gain stage is essentially as set forth in the SSM-2017 data sheet. I constructed the two SS preamp channels on separate perforated ground-plane prototype boards using high-quality coupling capacitors and other parts in the signal path. Output buffers are a four-transistor discrete design published by Walter Jung (The Audio Amateur 1988/No. 2, p. 24). Gain of 5 to 60 dB is selected in 5-dB steps using 12-position rotary switches. Two-position toggle switches control phantom power and signal polarity. A +/-15 VDC and +48 VDC external power supply couples to the barrier strip at the rear of the enclosure. I made the enclosure from a 19-inch aluminum rack panel, 3/4-inch aluminum angle stock, and some scrap aluminum plates.

Through use of this preamp I was satisfied that the SSM2017 performed quite well as a neutral, quiet solid-state preamp solution. With a transparent and detailed high-end, I used the SS channels on drum overheads for many sessions, until the HYB unit took over that role with a more tubular tone. I subsequently used the SS channels mostly on tom-toms.

It's too bad Analog Devices had to discontinue the SSM2017 chip, likely thanks to the realities of competing in a cell-phone world. THAT Corporation has been promising a drop-in replacement/upgrade for the SSM2017 for a few years now, but that product has not materialized as of early 2005. Luckily, Burr-Brown's INA103  instrumentation amplifier chip is readily available and sounds at least as good as the SSM2017. I picked the INA103 for VIHYB.

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