Oh sweet, so better sound with upgrading the BUF634's PSU decoupling?
It's modding time! I don't have good extra electrolytics, but I know I can count on MKP1839 caps to do the job really well anyway, ha
A lot of my favorite DACs use AKM chip, from the xDuoo to the Aune S16 and the m9xx... But some I don't really like, including the Modi 2, the Audioengine D1 and the Jotunheim. The Jotunheim is actually a very good amp, but the original DAC chip was surely disappointing. That said I strongly recommend you trying out the MB version, or at least get a Modi MB to go with it.
Those "Multibit" DACs are no longer AKM DACs, though.
Well the O2's design doesn't really support op-amp rolling actually, it was nWavguy's intention to reduce the impact of op-amp rolling. What I liked about the O2 was that it really keeps the same sound sig from the DAC and the headphones, not adding any colors - which I feel is not possible on cheap amps and also aligns with your opinion that the O2 isn't quite "musical"...
He "failed"
The O2 in practice is a very worthwhile opamp test bed. Great way to hear how ugly and colored those ancient NJM opamps sound versus modern stuff like ADA4610, AD8510, and ADA4075.
"not adding any colors"
That's an exaggerated way to put it. O2 does have a sound of its own.
Have both and can confirm this.
The USB DAC on the XDuoo is one thing holding it back, and it's worth listening to from a dedicated desktop DAC if you're using it as a desktop amp. I noticed popping in a few instances with the onboard. It also enjoys shutting off and on constantly with loud transistor clicks each time, and it's quite annoying. For a portable DAC I can't complain though. I don't know about the optical DAC--which might be better. With an external DAC though, I found the amp section capable of higher resolution than before, and while it is a little bit on the bright side for my taste, it is close enough to the line run my Edition X (warm headphones seem to pair well). I'm actually curious about further DAC scaling at this point.
There is a quality to the presentation that I'm not sure how to describe. Holographic might be the word. I was listening to Beck's "Midnite Vultures" the other day and just got lost in it. It's not perfect. There are albums here and there that are inexplicably harsh or hazy. For the price, I can't knock it though.
I wonder if my XD-05 is a good one now? I find that the internal amp is the bottleneck, not the DAC. Perfect excuse to bust out my awesome Meier-Corda Stepdance amp, haha!
The Xduoo DAC sounds rather big for a portable DAC, the separation is just impressive versus the plethora of compact DACs I've tried over the years. Not as natural-sounding as my iBasso D7 and FiiO E18, though significantly higher-fi than the FiiO otherwise.
Going to install an OPA1692 because of it's uber low current draw as soon as my lazy@ss solders another one onto an adapter. I gave that opamp a go in my modified O2 and love it. If I end up disliking how the bass boost sounds with 1692, I'll give AD8512 a shot instead, another really great opamp that I'm fond of. Then if not, perhaps ADA4075 as I've a spare now that it's no longer in my O2.
I lost interest in the V5i, reading how it triggers the internal protection circuits and causes odd behaviors and another guy in the opamp thread saying how it can cook certain chips ahead of it in circuit paths because of its huge output drive. Weird thing I'd rather not stick in my gear, basically. I care more for the DAC anyway.
Also, very overpriced for what it is, hahaha
Shoot, adding caps on those buffers won't be so easy if I want to be able to close the case.
I can't find the rest of my opamps right now, but ADA4001 works well enough. It doesn't have the tightest sound, but it is the most transparent and neutral-sounding opamp in my arsenal. The bass boost isn't as nice with it as with the stock opamp, but it is close enough. 8512 is a no go, the bass boost sounds poor with it.
