Not with the EAR Power Amp, but I used a Music First Audio Clone with my Audio Research Ref 75 for some years and was very pleased with the results. Ultimately, I marginally prefer an active valve Pre, the Modwright 36.5, but it is marginal.
If you wanted to try the MFA clone, PM me. I'm not committed to keeping it. It was built in Hungary with the same circuit and Stevens and Bilington Transformers, as the MFA Baby Reference. I actually got hold of the Baby Reference to compare and couldn't hear a difference, others thought they could. Still, when this cost £950 and the Baby Reference over £5000, it seemed a no brainer.