I tried to search for this all over, but it may be too ambiguously worded. I just got a 50' speaker cable, to allow me to have my head in a control room away from the cab in a live room. I had my head connected through my countryman and was playing with impulses vs my mic setup on my cab. When I muted my channels I heard my amp making (audibly) an output of what I could hear my cab making, only very high high (8kish-above) coming specifically from the output transformer. Since I have never heard my head apart from my cab, I don't know if this is a normal occurrence.