Concept IR-2100 (1980–1981)
Documentation on the Concept IR-2100 is thin: no brochure text, no service material, and no confirmed production dates survive in the Archive's records. The date range in the title comes from the two known period reviews, not from a manufacturer's model-year listing. What the record shows is that the IR-2100 was an outboard audio control unit — it connected to a receiver or amplifier's signal-processor/tape-monitor loop through a heavy umbilical cord, and it offered no tape-monitor switching of its own to replace the loop it occupied, as High Fidelity (November 1981, p.48) noted in a New Equipment Reports test.
The High Fidelity lab review documented solid measured behavior: the unit's warp filter cut response by about 10 dB in the worst-warp region around 5 Hz, adding to the phono section's fixed infrasonic rolloff for roughly 20 dB of subsonic attenuation; measured stereo pilot intermodulation was 0.092% and mono IM distortion 0.068%. A separate review in HiFI-Stereo (December 1980, p.54) was most struck by what the IR-2100 did to the soundstage: it widened the stereo image, at times dramatically, extending it beyond the speaker boundaries and adding depth both in front of and behind the speakers. The same review measured frequency response flat within 0.1 dB from 10 Hz to 20 kHz, and in bypass mode, 1 kHz distortion at 3 V output was −92 dB (0.0025%).
Exactly how the IR-2100 produced that spatial effect is not preserved — the surviving review text cuts off before describing the circuitry — and no other documented details of the model are known. Until more material surfaces, these two reviews are the entire record.
Known facts from period reviews:
- Outboard control unit; connects via heavy umbilical cord to signal-processor/tape-monitor loop; no tape-monitor switching
- Warp filter: ~10 dB cut around 5 Hz; ~20 dB combined with phono infrasonic rolloff
- Stereo pilot intermodulation: 0.092%; mono IM distortion: 0.068% — High Fidelity, Nov 1981
- Frequency response flat within 0.1 dB, 10 Hz–20 kHz; bypass-mode 1 kHz distortion −92 dB at 3 V — HiFI-Stereo, Dec 1980
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