4K headphone + headphone amp/dac system recommendations please

My fav is the RAAL SR1a, but I won’t recommend that since it is a detail king. A very engaging and musical phone is the ZMF Caldera Closed. I was very surprised I liked it. I was at a mini-CanJam meet and a couple of folks there who had cost no object phone systems gave me to listen to the Caldera.

Caldera Closed LTD Walnut Burl – ZMF Headphones  ($3300)

I have a Schiit AsgardX headphone amp with the MESH DAC. It is surprisingly good (the DAC). The amp was expected to be very good since it is based on the Schiit Mjolnir 3.

Schiit Audio: Audio Products Made in USA  $549

I was planning on getting the Caldera Closed to use with my AsgadrX but decided to save cash and got the Meze 109 Pro used for $500. Since I do not listen to this bedroom system much it was a good choice.

BTW - that CanJam show in NYC had the introduction of the new Allnic ASRA DAC. I heard the $6.5 ASRA headphone amp at the min-CanJam and it was superb. I am trying to get my friend (who sells the ASRA) to convince Allnic to add preamp out from the amp so I can use it as both a preamp and headphone amp.

Well, I had a response with links and comments that disappeared into thin air. So, this will be shorter. 

Are you willing to consider used or just new? Are you set on dac/amp combo or would you consider separates?

In regards to headphones,  I second the Sennheiser HD6 family. I would also look at ZMF, specifically the Atrium Open. They also have a new planar model being released that is supposed to combine the warmth/lushness of the Atrium and the detail of the Caldera. It's called the Tessidera. You might look at the Focal Clear OG as well. 

When it  comes to amp/dac combos made in the USA there's not a lot of options. I think Schiit, which yyzsantabarbara mentioned and you own is a good option. I nearly purchased the TEAC UD-701N which is a precursor to the UD 507 you're considering. Here are a few others to consider:

1. Black Ice Audio Aries
2. Violectric DHA V226
3. Mytek Liberty DAC II
4.  ifi Pro iDSD Signature  Made in UK, but 2 offices in US
5. Rupert Neve Precision DAC

Someone on this forum (early 2025) recommended John Masseria (JM Audio Editions) as a headphone savant. Handmade and sepcifically tuned headphones based on YOUR request. And good to look at with choice of woods and finishes.

https://www.jmaudioeditions.com/closed-back-headphones

Also very well priced. Worth a chat with him to match with headphone amps / DACs.

Good luck.

Just a follow up on JM Editions

I requested cans with similar level of detail as my electrostatic speakers with tight bass. By providing him with the spec details of my headphone amp and DAC, he recommended:

XTC2 openback with 50 mm beryllium driver, 64 ohm at 101 dB efficiency, extended blissfull tuning. All of these parameters are customisable. With 3 sets of ear pads

The results were spot on.

@stuartk -I’m going to second the recommendations made by @johannm 

I have a pair of JM Editions XTC21 with extended blissful tuning (say that 3x fast) and at one time, before getting a Quicksilver headphone amp, was driving them with a Violectric HPA. The combo provided the sound/tuning you are looking for, and as they say, "Punches above their weight class." This will give you ample funds to get a decent set of connects, also.

David