Advent Model 100A

Name: Advent Model 100A
Brand: Advent

The Advent Model 100A is an updated version of the original Advent Model 100 Dolby B noise reduction unit, introduced around 1971-72. Not much is documented about its full specifications, but the period record makes clear what the changes were about. The Model 100 had been the most flexible home Dolby unit for more than two years. The 100A brought "unspectacular but important engineering changes" to match it to every likely Dolby application then and in the foreseeable future (Audio, May 1972, p.41).

The biggest difference from the Model 100 was input flexibility. The 100A dropped the built-in microphone preamplifiers and offered two line inputs with mixing instead. An accessory stereo microphone preamplifier, the MPR-1, was available for an additional $20. It was designed to accept balanced microphone cables and was powered from the 100A itself (HiFI-Stereo, December 1971, p.70). The Dolby switching was also reworked, so the unit could handle signals - from tape or FM broadcasts - that had already been Dolby-processed. As High Fidelity (April 1972, p.32) explained, this meant you could make a Dolbyized copy of a Dolbyized tape, using the 100A's Dolby circuitry only for the monitored signal, whether from the original or the copy.

Almost nothing else is recorded about the 100A. No original price, dimensions, frequency response, or distortion figures have surfaced in the available documentation. The original Model 100 sold for $250 (High Fidelity, January 1971, p.40), and the 100A likely carried a similar price, but that is conjecture. The 100A was not a radical redesign. It was an engineering refinement that added switching and input options.

Type: Dolby B noise reduction unit (home tape/FM application)
Inputs: Two line-level inputs with mixing
Microphone input: None built-in; optional MPR-1 accessory stereo mic preamp ($20)
Dolby switching: Capable of decoding pre-Dolbyized signals from tape or FM
Predecessor: Advent Model 100