Actually, I can't believe I missed this...   Is your filament grounded at any point? It looks like you're grounding the negative side of your filament.

Nah man, sorry. I'm really out of my element with stuff this low frequency.   I would say that you need some inductive chokes on the B+ supply to the tubes, but I have no idea how that does anything with the audio frequencies.   Another shot in the dark, how clean is the DC coming into the...

Yeah, any speaker (or headphone) output should have 0V DC. Your design looks like it's possible for there to be DC on the output, which is why I asked.

Hrm.     Is the output transformer grounded on both sides? I'm not sure I'd do that.   How much DC do you have on the output?

Fair enough. Most of my experience is with tube RF amplifiers. I've yet to build a headphone amp.

  Without doing a major chassis rebuild, my suggestion is to run a ground wire from each component that needs a ground to a central ground. Quick and easy way to do this is the following: To further explain what's going on, I found some pictograms. Just ignore all of the amateur radio stuff...

Yeah, you need an earth. That will probably fix it, but you shouldn't stop there -- take the initiative to build a really killer amp. You've taken the first few steps and gotten yourself a working (but unsafe) amplifier. Now just make it safer by adding fusing, earth grounding, a good...

Fiber washer, nylon washer, card stock treated with resin, or a custom 3d printed washer.   Or buy another, if you don't mind paying shipping again... Which personally I hate.

OK, first thing you need to do is stop touching things while the amp is plugged in. You're going to wake up across the room or wind up killing yourself. HV isn't something to play around with. It's not worth dying.   My background first so you understand where I come from. I've been an amateur...

I've owned all the impedance levels that Beyerdynamic offers with the dt770, even the 32 ohm version.   Never have I had that issue -- then again I only buy direct from them.

Have you tried using an amp?   My DT770s don't sound nearly as good without an amp as they do with one. Even something as cheap as a Little Dot Micro+ helps. (Which I just discovered isn't made anymore.)

I've been away for a while. Life does that to you.   I recently moved to a cubicle at work, from a lab with pretty good audio isolation, so I have to live with headphones now. I have a set of DT770 headphones from the HifiManufaktur service they offered in the EU.   I've got a Chinese 6N3J...

My first pair of Super.Fi Pro 5's broke. I emailed UE, and I was dealt with in a quick professional manner. I was sent a new version 2 pair (I had the v1 previously) and I would do it again. I don't think it's the earphone that is designed to be low-quality, I think it's the plastics used...

Call up UE and see what they say. It might be covered under the warranty. I know mine were.

I fully reccomend the M-Audio Studiophile AV 30 or 40. Both are great bang-for-the-buck speakers, and they're compact enough to use on a small desk. For the sound card: try your built-in card at first, because it won't cost you anything. A lot of built-in cards now offer S/PDIF, which the...