I didn't want a DAC amp either. in a perfect world, I'd have a pure power amp, a couple watts and no preamp section or controls that I'd run off of my Freya +, which I began doing as a baseline. On its own, using my plex server as a source via USB, it blows my speaker DAC & pre out of the water and I've yet to mess with the op amps. Granted, prior experience with Fosi's Z_3 line, I own 6 ZD3 that are used as mono blocks to drive my 3 way horns and are modded with Burson V7 Vivid, Sparkos 3602 & Burson V7 Classic on the woofer, mids and tweeters, respectively and I'm quite impressed with them. That, and finding one open box model at 40% off and it was a no brainer. I'm new to dedicated headphone setups, but to my ears, this sounds very good and effortlessly drives my 32Ω KLH Ultimate One open-back headphones.
I have been continuing to listen to the ZH3 in its stock configuration and it continues to impress. I may actually prefer it as a DAC/Amp than using my Schitt Bifrost 2/64 & Freya + as the front end. It's really remarkably neutral sounding and makes my KLH Ultimate One cans sound similar to my 3-way horns with regard to frequency response, sensitivity and dynamics, and edges them out with even better phase response, soundstage and imaging. I have a pair of MUSES02 op amps and a pair of Sparkos 3602 that I will eventually roll into it, but unlike my ZA3 mono amps, I haven't found a need. While the ZA3 sounded decent, but slightly "off" compared to the Class A/B amps I own, the ZH3 sounds really good out of the box. It has 6 oddly named filters that describe the sound, rather than the filter topology: Pwr. Dyn, or Powerful, Dynamic, with a sharp roll-off; Neutral. Bal, or Neutral Balanced, with a slow rolloff, ; Ext. Highs or Extended highs, with with a short delay & sharp roll-off for detailed highs; Well Deff, or Well Defined with a short delay and slow roll off for clear & well defined sound; Nat Smooth, or Natural Smooth with a super-slow roll off for a natural and smooth delivery; and Precis Analy or Precise & Analytic, with low dispersion for a precise & analytical delivery. After very briefly trying these filters, I opted for "Neutral Balanced" and haven't done much else. It also has bass and treble tone controls and a tone circuit bypass, which I have engaged.
All and all, I find this to be a rather pleasing DAC/HPA; granted, it's my first, so my frame of reference is limited to my mothers' Marantz receivers and Koss 4AA Pro headphones that I used as a child in the 70's, various earbuds that I used with phones and iPod Shuffles in the first two decades of this century, as well as the headphone output on my current AVR, using cheap Tascam headphones that I used as tracking monitors in my home studio, neither of which ever presented a compelling use case for headphones and a dedicated amp. I might actually be starting to get it now. I'm homebound, recovering from surgery and I've spent more time with cans on my head than listening to speakers, in part because my partner works from home 4 days out of the week, sitting just 8 feet behind me in my MLP, but I've also been listening to them because they're just so darned pleasant sounding! It's really quite nice.
My next steps will be to try the XLR outputs for the DAC and compare it to my Schiit Bifrost 2/64 through my Freya +, and also as a standalone preamp/DAC, directly into my DSP pre/processor. After that, I'll roll op amps, which appears to be an even easier process than on the ZA3s, removing just 2 screws, sliding out the front a little & disconnecting a pair of ribbon cables, then sliding out the back to access the op amp sockets, reversing the process to close it up. Easy peasy.
