MI-SI Acoustic Trio Endpin Preamp

Installed (in strict accordance with the instructions) in a parlour guitar. Upon first use, after one song I had to change to my spare guitar which is fitted with a Fishman Fluence system as the Mi-Si was struggling to amplify the guitar enough to be heard. I sent it back to Thomann, who returned it six weeks later and declared that there was nothing wrong with it. I've reinstalled it, made sure it's charged and ... it's still much quieter than the Fishman in my spare guitar. It's a real shame, because I like the battery free nature of the system and it's well thought out and put together, but for all practical purposes, it's unusable and is £166 wasted.