OP,
I am really sorry to hear about your problem. I happily have not experienced this kind of issue… well, on a device that did not have a high range / low range switch. I have been following the thread expecting someone to chime in, “Yes, this is because the Bryson…. Xcxddcvfgyml 10volts…. While the Classe…. Shhtcverjkkk… I am sure someone will. This has to be a known incompatibility. These are two well know brands.
What to do? Sell the Bryson… I assume the problem must a lack of adaptability of the preamp, that is it’s function. I would never add additional equipment or deal with the symptoms. Verify the problem is the preamp and get a better one. I have been in this pursuit for 50 years an don’t remember having this problem. But then my memory isn’t what it used to be.