Power consumption Mk3

I have been trying to work out the power consumption of a MK3. The tube filaments consume 38W. We typically use a 3A fuse based on typical Dynaco stock. That's 360W. I do have a power meter I will eventually hook up the Mk3 but I was wondering where is the other power consumption? I would assume that in use there is consumption in the output transformer. but if the amp is rated for 60W is it fair to add that to the 38W for the filaments to arrive at approx 100W total consumption? There are losses in the transformers too so I am not sure what the factor would be there, but i doubt we are even close to 360W.

Is the stock fuse rating of 3A too high?

I used an inline power meter to the AC mains and measured my MK3. I am using Tung-sol Re-issue 6SN7's and 6550's with a JJ 5AR4. Stock vintage transformers, 8 ohm load on 8 ohm tap. Direct line in from a CD player of my burn in track which is guaranteed to be at 0dB (all bits)...

115.5 VAC on line
Initial start: 0.52A, peaked to 0.7A
Fully on with no input: 1.25A
Full volume: average 1.8A, peaked at 1.93A

So I guess that's why we use a 3A regular blow fuse. I might just put a 2.5A in there just to be safe, I rarely run it full blast.

That all sounds about right. I always use slo-blo fuses on tube equipment due to the turn-on surge (which is mostly the filaments),
so you are safe with either a 3A fast or a 2A slo fuse. See my notes also on your power transformer question.

There is also power consumption with no signal, electrons are flowing through the tubes, called the operating point. Amplifiers are not 100% efficient.

All you have to do is feel the heat coming off the amp and that tells you where your power consumption is.