I have added the Turn Island Systems “Product Satisfaction Policy” to our “About” page. This has always been our intent, so here it is in writing:

If you purchase a Turn Island Systems product and you are not happy with it for any reason (excluding obvious damage or abuse), return it to us and we will refund the purchase price less our shipping and sales tax costs. Even if the product works as specified, if it does not meet your needs you are welcome to return it for the refund.

https://turnislandsystems.com/about-turn-island-systems/

“Any reason” means just that. For example, if it turns out that a preamplifier or filter doesn’t actually help your system performance (which can sometimes be tricky to determine), or you for any reason decide you don’t want it, feel free to return it.