Chan
Thought you had buzz in one speaker only. Ground loop is often louder in one speaker, not always though.
You had CJ amps before the Art Audio. Did you have a buzz with the CJ? If not, could be the transformers on the Art Audio or one of the tubes (possibly going bad). Low powered SET amps are often guilty of displaying audible hum or buzz. Won't mention brands in deference to the manufacturers, but it is not that uncommon.
Do you have another amp you can substitute?
Thought you had buzz in one speaker only. Ground loop is often louder in one speaker, not always though.
You had CJ amps before the Art Audio. Did you have a buzz with the CJ? If not, could be the transformers on the Art Audio or one of the tubes (possibly going bad). Low powered SET amps are often guilty of displaying audible hum or buzz. Won't mention brands in deference to the manufacturers, but it is not that uncommon.
Do you have another amp you can substitute?

