Personally, I have not had good experiences with the Oliver M49 circuit. It was noisy like hell. I have tried tons of different 5840 tubes, from Thompson, Raytheon Philips, tubes from Royer... tried different capsules, from 3U M7 to various Chinese capsules... I would definitely lean M49 builds on the original M49c circuit and use that. The noise level is not worth mentioning anymore, and a much better, fuller sound. The few components less are really not worth not building M49c compared to the Olivers. I have modified all my 4 mics to M49c. They all sound just super now. By the way... the sound changes dramatically better and really open if you turn the 8pF "balancing" capacitor down to a 2pF Glimmer Capacitor. Regards