Might be a bit late to the party here but I really like your design approach that takes direct feedback from your customers on board. Former Naim user here and I have to say it's great to see the VFM that's coming from the affordable end of the hifi world these days. I used to be quite dismissive of the cheaper stuff but what changed it for me was the Allo products based on the Raspberry Pi. Affordable and they sound awesome. Such a shame that Allo seems to be dead (maybe Fosi could revive the concept! I use Moode on my Allo devices and it's been excellent. No need to reinvent the wheel)
The DAC / Pre-amp idea is great IMO. Absolutely makes sense to have all the switching in one place. This is exactly the kind of product I would go for in a hifi system. A few things I would be looking for:
• DAC in the pre-amp but keep the streamer as a seperate product (nice to have options here, update as technology progresses without having to mess with the major components of the system)
• Maybe a few options of different DAC modules at different performance / price points. Would be nice to be able to upgrade performance without changing product. Start with something cheap / accessible but be able to swap for something premium at a later date. Same goes for power supply options as mentioned below. This could then be Fosi's main pre-amp and the heart of your product line, customisable as the user wishes / can afford.
• Volume knob with fixed ends not an endlessly spinning type (the only volume knob in the entire system. Bit confused as to why the ZD3 / ZA3 combo gives you two. Who needs two!? A bit of a turn off for me)
• 2 x analogue RCA inputs. Could go one of two ways here. 1. no digitisation meaning no mucking with the source signal. 2. gets put into the digital chain allowing DSP ie. a parametric EQ for speaker tuning / room correction. Would be nice to have the option (switchable) but that's probably getting too complex / expensive.
• Minimum 3 digital inputs (USB, coax, optical)
• Bluetooth
• Make the screen simple, clear and modern. No faff. Make sure it can be set to turn off automatically or be in an always on mode.
• Switchable HP filter for setups using smaller speaker and a sub (ideally with a few different frequency settings)
• Different power-supply options at different performance / price points (I guess Naim brainwashed me in this way but Fosi already does this anyway). And why not put them in a proper case so they can be displayed in a rack with the other components rather than just stuffed away messily in the back somewhere!? I have the 48V/5A supply here and it's already fairly well built from what I can tell so I can't imagine it would be a huge leap to put it in a proper case.
But most importantly an emphasis on the SQ performance of the DAC (so that it is intended as the main DAC in the system and the only one you need, not just an add on for convenience). Also great SQ performance from the pre-amp. Would be nice to see a 2 channel Fosi amp much like the mono blocks (no volume control) to pair with the Q8. Keep up the good work