I do know the M100, the bigger brother. Great, but with a few simple tweaks it gets better. I'm not a big believer, but change the bellwire inside. And update the filtercomponents, especially the capacitors, which, after 30 years, might not be performing as they should be. Here's a link about the upgrade of the M100:
http://forum.audiofreaks.nl/index.php?topic=7163.0
Unfortunately in Dutch, but the pic's might speak for itselfs.
http://forum.audiofreaks.nl/index.php?topic=7163.0
Unfortunately in Dutch, but the pic's might speak for itselfs.