The (formerly) extremely-rare EQP-1S3 has the same wide-bandwidth line amp as the EQP-1A3, but has modified low-frequency boost/atten response curves, adds 2 additional peak boost frequencies (1k & 2k) and most-importantly adds 2 high-frequency shelf boost curves (5k & 10k corners) to the sonic palette. The originals included 6k peak boost in place of the 16k and that’s the way we built them initially.

But we had so many requests from customers for the 16k and so little interest in the 6k that we now build them with the 16k peak boost center.