Hagerman Audio Labs iRIAA2

The iRIAA Filter is a two-channel passive inverse RIAA response filter for use in testing phono preamplifiers. Unlike traditional networks, the iRIAA Filter includes a correctly placed upper 3.18us (50kHz) corner in its transfer function. Output level is switchable between -40dB and -60dB. Frequency response is accurate to within +/-0.5dB from 10Hz to 100kHz. See my original design paper from 1998.

If you're interested in burning-in a phonostage, consider the FryBaby2 as it will also do cables.