"Can you plug one Niagara Series product into another?
Please do not. As all of the current Niagara Series products utilize a linearized filter, plugging one into another would place two filters in series, and, in this instance, more is not a better thing… Doing so would create non-linear (inconsistent) filtering via resonance ringing modes. In many instances, parallel operation can work, but series operation should be avoided."
https://www.audioquest.com/page/aq-niagara-series-faq.html
Please do not. As all of the current Niagara Series products utilize a linearized filter, plugging one into another would place two filters in series, and, in this instance, more is not a better thing… Doing so would create non-linear (inconsistent) filtering via resonance ringing modes. In many instances, parallel operation can work, but series operation should be avoided."
https://www.audioquest.com/page/aq-niagara-series-faq.html