I'm sure that you are correct. :-)

Vibration (as opposed to hum) most often occurs when there's an unstable transformer in the circuit, which would itself be a reason for the company to service it under warranty, at least within the limits of my experience. Cheers. :-)

It’s not unusual for some circuits to hum when there is no interconnect cable attached because the cable itself MAY be the only way that the amp is truly grounded, though, yep, there can be many other sources of hum.

It should / could, but you might need to use more than a few layers of it and possibly solder a ground wire to it and connect that to a “drain” ground post of some kind (or not). Please remember that aluminum as all metals conducts electricity. Plus, if the Mu metal is already cut to size with...

Only Mu metal needs to be annealed (heated then cooled without being shaped again) in this context because it has a dense molecular structure that gets “disturbed” by any and all metal work. No other metals that I know of need to be annealed after shaping to block electromagnetism.

Sorry. What I meant but did not express well is that natural magnetism can only be blocked by a Mu metal alloy that has been annelead after shaping. Electromagnetism can be blocked by any metal and, in all cases, the thickness of the plate/board does add to the damping effect on the magnetic...

Mu metal only blocks natural magnetism. The kind of RFI you would get in an amp like the WA33 would be *electro*magnetism, which can be blocked by any metal but copper is often considered the best. I only mention this because real Mu metal is very, very expensive; but copper is not. Cheers.

Sorry, but what kind of “board” can one get that would reduce the hum? I would think that swapping the tubes could make a difference. My thought would be that—with an amp like this—you would want to use the very best headphones that you can and not headphones so efficient/sensitive that they hum...

I’ve tried planers and electrostatics, am very fond of Stax; however, my two current favorite headphones are the Fostex TH-900 and the Mr. Speakers Ethers. They both just sound so musical and natural. The Fostex are dynamic / moving coil and the Ethers are very fine planars. :)

I tried the Abyss and the Utopias with both a Cavali Liquid Gold and the Woo WA5-LE with tube upgrades, and in both cases the Utopias sounded much more like music to me and had vastly better build quality, but YMMV.

My experience, too, most notably with the Woo WA22.

The Utopias are definitely warmer sounding than the HD800’s in some ways. On the other hand, they cost at least 3X more. So, no offense intended at all, what would you expect?

I agree with your comment about the TT, but the balanced comment is not spot-on. Many components use a balanced topology that then requires balanced versus single-ended cables and vice versa; plus some SE components are transformer-coupled and sound best with balanced cables; it all depends.

I could be mistaken, but I think that, when you have a fully balanced setup like that, it’s entirely possible that the XLR will sound better since all things cannot be equal. In a system that’s part RCA and part XLR, I do think the RCA ours sound a bit better than the XLR’s, but there no...

I have read that back a ways in this thread but have not tried it myself. I tried the TT going into an integrated amp with a pair of passive speakers and a Woo WA5-LE, etc.