My general advice would be to stay away from ESS Sabre DAC Amps. Despite their low noise floor (SNR) and impeccable measurements, they are often bright, incredibly resolving but at the expense of sounding artificially clean (or what some would call the opposite of musical/organic/analogue sounding). And coupled with a brighter sounding iem like the PR2 (with fast transients and technical capabilities), it doesn't make for a good synergy. You want a warmer, thicker sounding DAC amp. DAC Amps that incorporate a Cirrus logic chip or AKM may be more beneficial for you.
tl;dr: I agree with you and have done the same, but I think the amp itself has more effect on the sound than the actual DAC. Ideally the DAC output should be flat, and any sound coloring (for better or for worse) should come from the amplification. In small devices like a dongle there's only so much you can do to step-up USB supplied current into high quality power.
---------------->> old geezer rambling commences <<--------------
n00bs should know that there's a whole lot more to this than first meets the eye. We're talking
months years decades long rabbit holes of research, testing, and sampling with one's own ears. I'm not ashamed of being cheap in this hobby, but I will say that one of the reasons I went with the BTR3k over BTR5 was because of the 3's dual AKM chipset, even though it's "only" 24 bits and not 32. For pop and even most classical recordings I can't really tell a difference when using budget IEM between 24 and 32 bit. Still I wouldn't call it warm by any means. At least to my ears, the sound profile is a lot closer to neutral than the first reviews led on to believe but it is indeed a crystalline clean sound as advertised and it's been a great source that's about the same size as a cigarette lighter. IMO neutral is the ideal, but many chase after warm and that's fine. I think iFi are masters at this.
It's a shame that Tri discontinued the TK2 - that thing was a beast for < $300. It uses dual Sabre ESS9038 pros and the bottom end was really punchy and full without being colored. If you spot one used - snatch it up, you won't be disappointed. My only beef with those (including units like the Diablo) is the form factor. That class of amplifier is really constructed to drive full size over-ears; it's massive overkill for IEM and a bit wasted on most KZ products if we're being honest ...
Volume: reasons why I EQ
When used in DAC line-out mode with IEM of 25 ~ 32 ohms and 105 db/mW sensitivity, 80-85 dB output comes at a volume level of ~11 of 32 clicks on my BTR3k, and it's putting out ~ 115 mW at an ear damaging / soul-piercing 124+ dB at the full 32 clicks. Remember, it's not a mini dongle but this is still the
small one!
The output is not at all linear, either. At 85dB we're talking about less than 0.01 mW, and we're typically judging amps on being acceptable when they're over ~ 60 mW. When reviews talk about IEM and 32 ohm sets being easy to drive, this is what they mean. (you can calculate / play with the figures for different phones here:
headphonesty volume 'n power calculator).
Closing in on 90 dB on rock and metal tracks is causing pain in my ears and even 80-85 will result in fatigue after about an hour if I sparkle-up KZ's already notoriously trebly profiles.
The problem is that our perception about the quantity and composition of frequencies across the output spectrum can be wildly different at different sound levels for the same headphone. Because of this, my preference is to EQ boost to taste and spend most of my listening time in the 40-70 dB range. Right now I have the GK10s plugged in with a balanced cable at 61 dB and, at least for me, this is plenty loud enough for casual listening and I hear full range on the bottom end without EQ. ZEX Pro? I have to screw with them.
And then I have the PowerDAC 2.1 ... that thing goes to almost 600 mW balanced. I have to be very careful to not hurt my ears if using it with IEM. I tend to use it more for my over ears at my desk. I would describe it as ruthless in it's precision and presentation. For me this was end-game for having a details oriented amplifier of any size, type, or cost. There is some distortion and hissing at the top end of the power range, but you don't notice it after the volume comes up, and it's not detectable at all when using with IEM. With the CRAs plugged in balanced it's like my old Yamaha bookshelf speakers are sandwiched to my head. It's also energetic enough to be tiring - I don't actually use it all that often and have been snooping around tube amps for awhile to use as my main power source as I get older and my tinnitus less tolerant to IEM use.
Would a balanced output be so much more worth it for the PR2s or would the 3.5 mm output be enough?
As basking said, the single-ended KA11 is pumping 200mW at 32ohms - and the PR2 is only 15 ohms. At 200 mW on the KA11 you're still looking at big power numbers there, even single ended. I am tempted to toss one of these in the cart for myself to use with my growing collection of DD sets but I need more gear like I need more holes in my head. The thing I like about FiiO is that all their gear seems to be made to a high standard and is still affordably priced. Looks like you decided on the KA11 - let us know how it works out!
