First you need ECC31 to 6SN7 adapters. The next issue is that the Mullards draw 0.9A each. The ZOTL's fuse blows at 2.5A. You have to add at least the 12AT7's current times 2. It might work if you replace the ZOTL's fuse but that would probably stretch the limits (and void the guarantee, I would assume). So I would strongly recommend an external supply. Is it better that we use Mullard ECC32?
2/12/16 at 2:25pm