[LG V30 Questions & Answers] TheDannemand:
Thank you very much!

I am quite familiar with that excellent, excellent Android Authority article: It was one of the first I read about the V30 Quad DAC (although it's is about V20). It gave me an insight into the design of Sigma-Delta DACs that I didn't have before. And even though the author points out in he beginning that he is merely speculating about the implementation of ESS and LG, I have no doubt that the Quad aspect is exactly as he says: Summing up the signal from multiple parallel sub-DACs is a well known approach to reduce noise, essentially multiplying the current delivered to the OpAmp without increasing noise proportionately. There is no mention in that article of the different modes, but there is that quote from LG's Marketing Guy -- which I had forgotten, and which does indeed say that three DACs are shut down with lower quality sources or headsets!

Again, that take on the Quad DAC design was originally my understanding as well, after reading that article and others relating it to the three output modes. And it definitely makes a lot of sense: Instead of raising amplification (and noise) just add more current with more DAC units before feeding it to the OpAmp.

My thinking then gradually changed as I read up on the V30 thread on head-fi.org. I read all the 3,600+ posts there, it took me over a month, but was quite enlightening: Some of the members there are in a league of their own as far as understanding electronics and signal processing, having well trained ears, and owning tens of thousands of dollars worth of audio gear -- in the case of some including spectrum analysis hardware and software for objective measurements.

As you can imagine, there is some fierce debate in that thread about this very question: Does the output mode (Normal/Aux/HIM) affect the number of active DAC units or does it only affect the level of amplification by the OpAmp? Two members in particular debated this (about 50 pages ago or so, it's obvious when reading the thread) with one presenting very strong theoretical analysis backed up by diagrams from ESS (but no direct statements from LG or ESS spelling it out) and the other arguing that his extensive measurements and listening tests on a broad range of high-end equipment had shown no discernible difference between Normal/Aux/HIM modes as long as output was adjusted to the same volume level. (It is a known phenomenon that people claim to hear more details and clarity when the only change is that volume was raised slightly.)

In the end the "objective measurements" argument carried more weight with me than the "theoretical analysis" argument -- although complete certainty was never there for me one way or the other.

But on one front I do have certainty (well, almost anyway): Even if the number of active DACs vary with the output mode, I really don't think it matters as long as the mode is matched to your headphones/earphones/external amp. Here is why: Regardless of the number of DACs, the sound signature will remain the same. It's not like more DACs will add more bass or midrange or treble or clarity or detail or soundstage. It will only affect the noise level. And as such it is only relevant when amplification is raised enough for that noise to be audible. High output voltage is mostly required for planar magnetic and other headphones with low sensitivity; or if driving a power amp directly with no pre-amp (and even there Aux mode may be plenty). On sensitive, low impedance earphones (such as ones with balanced armatures) HIM is going to make you turn the volume way down. But you probably wouldn't be able to hear the noise even in Normal mode, because those sensitive earphones don't require much amplification in the first place. In other words, the noise problem that multiple DAC units is meant to solve, is only relevant when the signal is amplified enough to actually make the noise audible. And this, in turn, depends on the earphones/headphones/amp being used.

This has, in fact, been borne out by my own observations as I have played with the different modes on different types of listening devices -- although I don't have nearly the gear (nor the ears) like some of those head-fi dudes.

Like everybody else, I would much have preferred for LG to give us the control. But alas, given the risk of hearing damage and the number of lawyers on this planet, that was never going to happen. In light of that, LG's choice to tie the output voltage mode (regardless of whether it is implemented by summing up DAC output current or by sheer amplification) to the sensitivity of the earphones/headphones makes some sense. The only problem is with headphones that have both low impedance and low sensitivity, such as planar magnetics. They need the power of HIM, but won't trigger it automatically. I am sure there are some others too. But outside of those, I believe there is too much time and effort wasted achieving HIM where it is not needed. Again, that's my belief and only that.

Thanks again for sharing that Android Authority article. Everybody should read that! And that quote from the LG guy does indeed speak to the implementation of the modes, as you said.

Edit: One thing I should have included in that long dissertation, and it gets back to my first reply on this subject a few posts ago: There is a third theory out there that the Quad DAC isn't activated at all unless >50 ohms headphones are plugged in. We can just dispense with that theory completely, as it is very easy to disprove simply by listening while toggling the Quad DAC on/off using <50 ohms headphones.