This page includes more untried ideas, and anyone wanting to try these newer versions should expect to encounter problems.
The next circuit is one I originally intended to be a feedforward circuit, but there is really no point reducing distortion any further than even the original MJR-6, so I have instead gone in an entirely different direction, aiming for low noise and using a direct-coupled jfet input. I am not entirely happy with it yet, so it is included here as 'work in progress'. First here is an earlier version:
This includes a 220uF capacitor and two diodes to slow down the switch-on to reduce the output thump as the output capacitor charges through the speaker. This is not essential, depending on speaker sensitivity, with my own speakers there is just an unobtrusive low frequency sound at switch-on. With other applications such as a bi-amp or tri-amp system with active crossover filters, this addition may become more useful to avoid low frequencies reaching high frequency speaker drivers. It may also have some point if a high sensitivity speaker is used, so it makes sense to include it in this low noise version.
Here is an alternative arrangement closer to the original MJR-6 :