That's possible. I wasn't thinking about power though. I was talking about usability and sellability. I'm talking about this from a business perspective. Most customers are going to want some sort of balanced output. Right now the 4.4mm is the most popular and everyone is expecting that, and they have spent money on 4.4mm cables. When the average customer sees the E01 and there isn't a reason for it to be SE only they aren't going to buy it. In fact iBasso had this issue. That pushes my thinking toward this being some sort of tube amp.
From business perspective, we don't look at E01 Audio Motherboard as a product, we treat N6ii as a complete platform and E01 is part of the building block of a complete "system".
The good thing about N6ii is that customer don't have to buy EACH AND EVERY Audio Motherboard, you just pick what you need and what you preferred. We provide two very good options if you need full features modules, our A01 and T01 offers balanced phone output and line out, with different sound signature, battery duration and synergy with IEMs differently. On the other hand, we can provide specialised Audio Motherboard for the very niche market segment. We don't limit ourselves with "every Audio Motherboard must have a balanced phone out" assumption. Yes, from business perspective, we see this as a limitation to a fully modularized DAP.
Now we can discuss the technical perspective: can we implement a fully differentiate circuit in E01 architecture?
While we are determined to do our best, we can't go against the law of physics. The E01 is our ultimate audio design within the physical and electrical limitation of N6ii architecture, lets talk about these limitation briefly.
We only have limited space on N6ii Audio Motherboard and discrete component required more space then the commonly used Op-Amp. If we implement fully differentiate audio circuit with discrete components, we need to double the components used in the analogue amplification. To do that, we need to find more space for the analogue circuit by replace some of the "larger" components with something smaller in form factor, for example, ES9038pro vs dual ES9038Q2M. In fact, we did compare ES9038pro vs dual ES9038Q2M during the E01 development, and we decided to stick with ES9038Pro as our ultimate Class A solution because the prototype of Pro chipset simply sound better.
The second problem is heat management. Class A amplification is low distortion on the expenses of low efficient, so the Class A amplifier operates at a much high temperature. If we implement Class A fully differentiate amplification in the sealed Audio Motherboard chassis, we will run into serious heat management problem, The DAP will either run at uncomfortably high temperature (that you won't be able to hold it on your hand or put it inside your pocket) or causing the power management chip to enter protected mode when the ventilation is insufficient to disperse the heat from the Audio Motherboard.
The final issue is battery duration. Class A amplification operates at very large current and it consumes a lot of power. Not an issue on desktop system with AC power supply but this can be a matter or life or death in portable players. For the record, Calyx-M (2014) was the first ever DAP (ES9018S-2M based) designed with discrete class A analog output stage. It was one of the best sounding DAP at its time but the battery only last 4-5 hours, reviews blamed short battery durations as the main reason for the relatively short product life of the wonderful. product. Our N6ii with E01 offers 7.5 hours of continuous playback after we have done everything we could to extend the duration. What happen if we implement the current design into balanced output? The battery duration will definite dropped significantly. It won't be as bad as 50% drop quite possibly at 4.x hours range. We consider this unacceptable for practical reason.
This lead to our final and most important question. Can Single-ended headphone output worth the title of Cayin's ultimate design in N6ii Audio Motherboard? Do we have to had Balanced output if we want to call it "ultimate"? Isn't Balanced always better?
As I said in another post, we provide detail information about our product, as much as we could, but we try to avoid subjective comment on our product. Similarly we'll leave this to our customers and reviewers to judge whether the E01 worth the claim of cultimate design. Let's stay tune for this.
