Tube Ampp Almarro low level hum

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.

It sounds like it could be some transformer hum since it goes away when you touch the amp on occasion. Not guaranteed to be the answer, but you might try tightening down the transformer bolts and or putting a dense heavy object on top of the transformers. You don't need any magic pebbles or crap like that, just a brick would do(doesn't have to be "magic" either), though not very pretty to look at. Place felt or rubber pads between the heavy object and transformer to keep from scratching it (beware that rubber may melt if those trannies get hot - use felt in that case). Use whatever you might have on hand and see if it improves and if it works you can look for something that floats your boat to put on there. Mapleshade makes brass "HeavyWeights" that they charge a bit for or you can go to a scrap yard and find some scrap brass or?

Good luck!

Yes, as Swampwalker said, or rather, let me paraphrase; Hum Happens. Not a defect or necessarily worn out (Could be loose bolts, which you could address). Could also be a drop in voltage (I think when you get on 10% or so you could induce some hum). Try the solutions I offered and see if that works. I guess that does deal with the symptom, but if it's just a loose bolt you've dealt with the problem. Try the weights if the bolt doesn't work. Could be tubes (remote chance) too. I'd look at the trannies first - not as a defect, but just for something loose or vibrating. I'd strongly suspect that given that it stops when you touch or move them.

I know just enough about this stuff to sound like I know what I'm talking about, or rather, just enough to be dangerous. To try to address your question, and someone will have to correct me on this if I'm inaccurate, but I think a tranny could break down (some of the binding element they use inside) and that could have that effect of exacerbating hum, BUT, as I understand it, that would be over a greater period of time than an Almarro amp using 6C33C tubes could be old (in other words, not likely). Still could be vibrating. I have a friend who owned those amps for a while. I'll ask him and point him to this thread.

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