Hello everyone, this is the follow up post to my earlier one about my op-amp rolling on the XD05-bal, it continues my subjective reviews of the different op-amp chips I tried for the benefit of others faced with a similar journey. As stated previously and repeated here for simplicity, all impressions are my subjective take on the chips listened to with my ZMF Verite open with Auteur perforated suede pads, each set of op-amps were tested for at least 2 weeks with daily use and with burn in when I wasn't using it.
The primary music I listen to is Metalcore (modern heavy metal) with some other Metal & Rock derivatives (Numetal, posthardcore, swedish deathmetal, dreamwave & such) the other genre I listened to is film score music (Hans Zimmer, John Williams), so my opinions should be taken with that in mind, on a subjective level I value a more linear active sound without rolling off at the bottom or the top, excellent transients with slam and some euphony in the mids, I believe I have a higher tolerance for brightness than the stereotypical audiophile...at least that's what I think, they seem to like a much darker sound than what I would prefer, so take from that what you will.
My audio chain is: Deezer HIFI/PC > silver plated USB > BRZHIFI DDC (digital to digital converter/clocker) > silver plated AES > XD05-Bal (BRZHIFI external linear powersupply) > ZMF stock OFC balanced cable (4 pin bal to 4.4 bal converter) > ZMF Verite open (Auteur suede perf)
AD827SQ: HOLY CRAP a portable unit can sound like this! A very serious upgrade that pushes the unit into desktop amp territory, a substantial increase in resolution and detail to any chips tried before and with a soundstage that is actually 3d now, not exactly a very wide soundstage no but much more "around you" and with excellent separation between instruments and some actual depth. Bass now sounds like it SLAMS in comparison to the other chips and has this almost physical texture, mids have this central presence as if it's rising out of the background, treble is quite extended without any form of sibilance or even any brightness, the MUSES were actually bright tilted, this isn't, the treble isn't accentuated in any way, it's just...there doing its job.
It's not perfect, the main downside for me was the clarity, it's not best id heard, the muses were definitely clearer (its bright tuning prbly helped) this chip sounds a bit...hazy in comparison, like the window to the music was now a bit dirty, the soundstage also as I said isn't the widest, on my IEMs which don't have the headphones naturally superior stage it sounded almost...restrictive, on the HPs it wasn't bad like that but you could hear how it was narrower.
The tone also has to be mentioned, I thought a lot about it and I saw someone else use a word to describe AD op-amp chips in general (not this one, the house sound) and on another unit but the word was right, he said "zippy" and it is, the notes are fast and dynamic, it's not exactly forward as in your face no, it's that the whole sound is energetic, like it's trying to capture what live music actually sounds like, it's the sort of thing you normally hear on desktop amps and hearing it from this unit was really something.
AD8620 soldered onto a DIP board: This chip had many aspects like the one above (AD827SQ) so I will focus mainly on what was different, the technicalities were a step behind the 827, the soundstage however opened up, in the sense that the width no longer had the constraint of the 827, bass slam went down quite a bit, the mids became almost softer and the treble was smoother. The main differences to me were in the overall tone, it was...smoother more airy sounding in the ephemeral sense, it made it all sound less solid, this combined with the reduced technicalities made it seem...breathy in the thin not much substance way, it wasn't exactly a bad sound no, it just seemed like it traded a lot of what made the 827 great for a lighter breathier sound.
As you have no doubt surmised, I had at this point gone toward the AD sound and was determined to explore the best they had to offer, I knew that part of what I was hearing was due to the nature of the chip type, specifically BIPOLAR vs MOSFET. I won't go into a very detailed tangent of what the differences are, would take far too long and is beyond the point of this thread but for the sake of this post I will try to summaries, BIPOLAR uses a current driven amplification like a diode or true solid state transistor amplification, MOSFET uses voltage driven amplification like a vacuum tube with the idea of giving tube characteristics to solid state, the 827 was bipolar and the 8620 was mosfet, the 8620 was also cheaper so I had to consider that was behind the difference in technicalities, with this is mind I went to the two last chips, the price jumped for them and while I can't tell you if it's what YOU should do, I considered how much I use this unit, the level of sound quality it would give and judged it worth it.
AD5962-8853801PA: ADs top MOSFET/JFET DIP8 chip, a very substantial upgrade in resolution and details over the 8620, no longer sounded so fake and breathy, soundstage was bigger with more open sides. Bass was highly textured but still had little slam, mids were natural and flowing and the treble was clean and smooth, very smooooth, the overall tone was now like...liquid, it was music that just flowed, the timbre was good, sounded very natural and had a lot of texture to it. The main thing about this chip really was the tone, now this was an awesome chip make no mistake, the technicalities, clarity & soundstage were top notch and now it just flowed...yet I did not find it particularly engaging, the sound being delivered was now...unrealistically smooth and laid back, I get it, this is an "Audiophile" sound (exaggerated smoothness) but it was now no longer like what live music actually sounds like. On a subjective level, and preference of tone is very subjective, I didn't like its delivery/tone that much especially with what I listen too, made it all sound like...background music, lacking in the emotional engagement or the physical relatability, I thought at the end that it made the music sound like elevator music, extremely high quality yes but still like elevator music.
AD708SQ: ADs top BIPOLAR/BJT DIP8 chip, WHOA! sounds like the 827 with everything cranked up to 13 and no objective downsides, seriously, the resolution and details went up and the clarity problem went away, now the sound isn't hazy or anything like that, soundstage definitely improved, it's still not the widest out there (below the jfets) but it no longer sounds like it has a wall on both sides constricting the sound, in a direct comparison yes it will sound narrower but its improved to the point that while listening to music you will no longer think "oh this sounds restricted", one thing to keep in mind, in a straight comparison to big desktop amps this XD05-bal unit doesn't have a very big soundstage period, while op-amps can change it, it still is under the parameters of not being very large to begin with, that's worth keeping in mind.
The bass is big, solid and slams without bleeding into the mids at all, it's still controlled and with this awesome very deep and detailed texture, really, the bass is a true pleasure on these chips, I've tried desktop amps that were grossly inferior in this regard, the mids are free of any constriction of the other bands pushing into it, so the sound is actually fairly warm and vocals have a rich textured tone, makes the muses/opa/v4i sound positively thin in comparison, the treble is decently extended, textured and absolutely free of any form of sibilance or grating hardness/digititus etc, this aspect I tested with a family member who is extremely sensitive to any form of treble harshness (I'm not) and he just kept listening to it and listening to it, didn't want to stop (literally), as someone who thinks of himself as a treble head, while I would definitely prefer it had some more shimmer and sparkle, it doesn't leave me feeling like its muted, lifeless and just lacking like the jfets/hdam/v4i did.
The tone is what I would call natural, like the 827 but clearer and bit better timbre, it sounds fairly close to...what live music sounds like (IMHE from many live concerts) maybe the treble is a bit smoother than life yeah, the overall tone is warmer and not quite as raw as the concerts but what's as good as live music? The overall tone is the AD tone that I elaborated on before, zippy, dynamic fast clean transients, not in your face forward but certainly not a laid-back kind of sound, much more of an emotional engagement sound, really draws you in kind. It's interesting how it came down to the two types of solid-state chips, now keep in mind this is just in the context of these op-amp chips on this unit, not a general assessment on BIPOLAR vs MOSFET, but for me 5962 was just...missing something, it sacrificed the magic for this faux tube sound of smoothness and sprawling soundstage, almost like it gave up the advantages of solid state for a pale imitation of tube goodness, ultimately the dynamically superior tone of the 708 in the emotional engagement and physical relatability was what made me firmly choose the 708 as my final chip that now stays in my XD05-bal.
With that my op-amp rolling journey ended, with these AD708SQs the unit is now clearly on the level of desktop solid state amps, I tested it against some desktop units and I found it to have higher quality of technicalities and this aspect of what I called more colour to the music but with a bit less slam and definitely a smaller soundstage, even with that I still strongly preferred listening to the XD05-bal, just really impressive what can be done in the portable size, with that being said its time as my all-purpose unit draws to a close as I am getting a proper vacuum tube setup for my headphones and this unit will then just be for my portable walking around with IEMs music, as it was always long term intended to be. I hope this review helps anyone who embarks on op-amp rolling and I will be more than happy to help, answer any questions, thank you and enjoy the music.
