The two-week return period starts when you take delivery of the amp. You then have two weeks to decide whether you want to keep it. If you decide to return the amp, it will need to be shipped back no later than 14 calendar days after you took delivery of it, so if you took delivery on June 1st, you will need to ship it back no later than June 15th. 336 hours should be enough to allow you to decide whether to keep the amp. 
Please use a tracked and insured service as you’re on the hook if the amp gets lost in transit.
I will process your refund within 48 hours of receiving your return, usually faster. Basically, I need enough time to determine the amount of reconditioning needed. You’re on the hook for all shipping costs and the restocking fee.
The restocking fee pays for me to recondition and test the amp, and for the loss I will incur when I sell it as B stock. I can’t with good conscience claim the amp is new when it’s been sold once already…
Some may find this policy strict, but it is clear and upfront. Returns cost money. That money has to come from somewhere. I can either make the person who returns the amp pay for it, or I can increase the prices of my products and distribute the cost of returns onto everybody. There’s no free lunch, unfortunately.
In more positive news: I am now able to offer rather incredible shipping rates on UPS and FedEx shipping. These shippers will get an amp to you in a few days, and overnight in many cases. Canada Post (and USPS and other postal services) take quite a bit longer these days, but packages are getting through.
You can find the HPA-1 here: https://www.tomchr.com/products/hpa-1
Tom