I have an Innuos Phoenix USB decrapifier reclocker, I wonder if these type of devices have a positive effect on sound quality or do they have a minimal effect if any
The 006 has a galvanic high speed usb isolator chip and the whole purpose of it is to make the usb input agnostic of the source. However, in reality, the better the source, the better the sound. Many say that I2S sounds better when they introduce a DDC in between but the fact is they have a poor/weak USB source. In my case with 005, a DDC deteriorates the sound since my source’s usb implementation is a lot better. There is no black and white answer to your question since, unlike analog, there are too many variables (power supply, noise, jitter, network) in digital that can affect the sound. Since you already have the Phoenix USB, try with and without and let your ears decide which sounds better.
On a separate note, the Phoenix USB chip is pretty ordinary and nothing fancy, it’s the power supply that makes it better than many, if not all, music server’s USB output.