JBL 5600-2B
Here's an honest complication right up front: no source in the archive uses the exact designation "5600-2B." The documented names are "Combat Amp 5600," "JBL 5600," and "JBL 5600 B" — so this page covers that amplifier family, with the caveat that "5600-2B" may be a variant, a revision, or a transcription quirk. If you own a unit stamped 5600-2B, you're ahead of the record.
What is documented is a ruggedized two-channel power amplifier. JBL's own archived product page rated it at 100W per channel into 8Ω (20Hz–20kHz, 0.02% THD), 150W per channel into 4Ω, and 300W bridged into 8Ω. Frequency response was spec'd at 20Hz–20kHz ±0.5dB, signal-to-noise at ≥100dB A-weighted, and damping factor above 200. Input sensitivity was 0.775V for rated output, with 20kΩ balanced and 10kΩ unbalanced input impedances. The front end accepted both XLR and RCA, outputs were five-way binding posts, and a bridge/parallel switch allowed dual-mono operation. It was fan-cooled in an all-steel chassis — the "Combat Amp" name suggesting military or industrial intent, though no source states that positioning explicitly.
Production years, original price, and dimensions are not recorded anywhere in the archive. The only market signal is a single Reverb listing for a unit in good condition with minor scratches, including its power cable — no asking price stated. No owner reviews, no service documentation, no known failure modes. Studio Sound (November 1975, p.38) ran a survey addendum that year covering professional audio gear, but the surviving OCR fragment doesn't reach the JBL entry, so no period verdict survives here.
Known specs:
- 100W × 2 into 8Ω (20Hz–20kHz, 0.02% THD)
- 150W × 2 into 4Ω
- 300W × 1 bridged into 8Ω
- Frequency response: 20Hz–20kHz ±0.5dB
- Inputs: balanced XLR, unbalanced RCA
- Outputs: 5-way binding posts
- Bridge/parallel switch; fan-cooled; all-steel chassis
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