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RE: Full blown Kal Rubinson review and in depth JA measurements....

Posted by AbeCollins on December 12, 2024 at 07:20:16:
Ric, I posted the link below to what I believe is the Buckeye page for their Purifi 1ET9040BA based monoblocks. Scroll down to the Custom I/O Board: heading where he lists the TI OPA1656 OP Amp.
[EDIT]: Even the Purifi 1ET9040BA PDF data sheet is a bit confusing. It shows the module gain as 14.4 dB so you're left to assume that the overall gain is due to the op-amp input which has 3 settings. The datasheet also shows the module input Z as 1.5kOhm diff & 1.3kOhm single-ended. I have to assume that the higher input Z in some reviews (and your finding) is from the input of the op-amp and I further assume that it will vary depending on what input resistor values the builder chooses to use??? Big question mark. Do you know how they come up with the real input Z because it's not clear to me.