Tube DIY Asylum

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RCA Phono Preamp Rolloff?

Posted by Triode_Kingdom on July 20, 2017 at 20:31:20:
I use SPICE whenever possible to analyze circuits I'm planning to construct. This evening I combined an inverse RIAA filter with the RCA phono preamp circuit. The result is a frequency response plot that's essentially flat over much of the audio spectrum, but there's a pronounced high end rolloff. At 20KHz, amplitude is down 3dB. I'm pretty sure this isn't related to networks in the preamp, so maybe it's the Miller effect at the 12AX7s. Anyone here ever used an inverse RIAA to measure their phono pre?