I recently asked Doug to do a couple of mods to my beloved C40... 1. Added switchable SS recto... 2. Sweetened up the voicing by taking just a bit of the high end off Amp came back sounding better than ever...really happy with the results...SS recto firmed up the low end even more, improved response and head room exactly as Doug had described and high end is much sweeter...WOW! Thanks Doug for your professionalism and skill in building an absolute tone beast!!