Believe it or not, I'm still trying to figure that out. The other night I got astounding sound w/the Final D8000 (a planar). A couple weeks ago, astounding sound w/my other planar, the Ori.
Results with the Atrium have been a bit mixed: several days ago I got a very large, spacious sound with a bit more treble than expected (total level of treble, I mean--actual sound of the treble was terrific).
This amp is a real project. Mfr recommended 300 hrs burn-in, which I did. But it may prove to be one of those devices that keeps changing sonically until ~500 hrs' burn-in. I say that because I've gotten variable sonic results in the time I've had it in my main system (after 300 hrs' burn-in).
Part of the variability was because I tried 2 different tactics to knock down the excessive gain of the amp (external passive volume controller; or pair of high-quality 10 dB in-line RCA attenuators). The in-line attenuators work well and have been in the system for past week+. I'll try the VO & Atrium on this amp again soon, probably over the weekend.
As for output impedance of each jack, I really can't figure out this design at all:
- Thanks to a "pigtail" from ForzaAudioWorks, I can use my typical XLR/balanced FAW cable with either the THR-1s 4-pin XLR output or either of its 1/4" outputs. Here's the weird thing--the level doesn't change, no matter which output I use. That can't be correct; the high impedance output ought to put out lower volume. But it doesn't work that way.
- Compounding the weirdness is the fact that the volume from any of the 3 HP outputs is at least double that of the line-level outputs that go my amp & speakers. Comfortably loud on HP is ~9:30 on the dial, while comfortably loud on speakers can be 2:00+ on the dial. I can't figure that out at all
- At first I thought the passive controller or attenuators were somehow acting differently for HP outputs vs line level output (not possible, but still, I checked). Running the amp w/no attenuation at all, the same volume different exists, but now the volume is pinned counterclockwise for HPs, barely getting above 7:30 on the dial before becoming intolerably loud, while the preamp output is @~9:30 on the dial.
So to say the least, there are some operational oddities w/this amp. Some of this stuff wouldn't be noticeable to anyone using it only for headphones and not also for preamping, as I do.
But in general, the sound I've heard since putting it IMS is really high level SS sound done right--strong bass, big/rich midrange, and very extended treble that is also delicate and nuanced. The headphone sound is strikingly good on some headphones. I'm putting in all this time and effort w/the THR-1 mainly because its core sound seems so promising to me.
More to report in a few days re sound w/VO & Atrium...