Tube Ampp Almarro low level hum

The transformers are very secure on the chassis. With the suggestion of the current, I checked my circuit and found some other appliances (a laser printer and scanner) that were plugged into different plugs on the same circuit. I moved those and had no hum for two days. Now it is back but much much lower so I believe it is a current issue. I can live with the current hum but I'll send an email to Almarro to see if they have any ideas. Thanks to all for the great advice.

There are some power re-generators that have the potential to put out a constant clean output. I believe PS Audio offers several. You may be able to spend less money on installing a dedicated circuit with isolated ground, but if the fluctuations are coming from the grid (outside your house) that may not do much. No guarantees that either will 'solve' your problem. Did you try placing weights on the transformers when they are humming (I understand they are secure)? I'm not familiar with the amp, but there's a possibility it could be that the input or driver tube may be causing it...or perhaps a bad socket or something could shorting somewhere. Just a few more thoughts. Do both channels always hum together, or just a single channel? If the latter, is it always the same channel? Contacting Almarro is a great idea, or course. You'll find if you do a google search on "Almarro 318B Hum" you will find you get a handful of hits - At least one I noted said they'd had theirs replaced.

This may not apply to your situation. One of my Threshold SA10e mono amps developed a low level hum that would come and go. Recently the hum would appear more often and became louder. I removed the balanced cable and reconnected. The hum went away and came back within a few seconds. I felt the problem was with this connection. I tightened the two hex screws holding the XLR input in place to 10 inch lbs. and the hum was completely gone with no return visits. I did the same to the other amp and both amps are now dead quiet at zero volumn. I hope this helps someone.

I placed weights on the transfomers and indeed that solved the hum problem. Then I tried using springs under the amp to isolate it and that solved the hum problem without the weights. Thanks for all the great advice to solve the problem.

Glad to hear it worked out! The spring solution is a new one on me, but I've found the weights can work wonders.