Do you know what the running use watt specs are? This would be very helpful to determine what the BTU generation is.
I have a watt use Device used to measure watts from an outlet. The 611 rarely gets above 65, and when just left on with no volume, it’s zero. The tubes probably have ongoing watt use and that would be interesting.
you have an interesting looking system. I didn’t see the 901. I see the mac amp and rack to the right. Is that amp rack on coasters. ? Would love to know the name , it's really nice.