Tube Ampp Almarro low level hum

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!

Jax2 - good thinking. If it is a transformer, is it humming because it is aging? Malfunctioning? Or is that just how transformers are? Can I address the source of the problem or just deal with the symptom? Thanks for your comment.

sometimes transformer hum can (as Jax2 said) just be the result of loose mounting bolts, sometimes not. Sometimes its just how that particular tranny is. Toroidal trannys are often less susceptible. One other cause sometimes is DC offset, IIRC.

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.