I own iDAC2 and USB input only.

I am definitively using both pre-amp and headphone amp modes. I permanently connect RCA cable to a pre-main amp to drive my speaker system. If I want to listen to music through a head rig, of course pre-main amp is turned off. I do not see any issue with that.

Pro iCAN does not have fixed output. When I use it as pre-amp to feed the output to the pre-main amp for speakers, I usually set the volume knob of pro iCAN maximum and the sound power level from the speakers is controlled by the pre-main amp. It is depending on your system, though.

I do not use any equalizer in the digital domain. Are you using a headphone amp hooked up to DAC? I recommend using the equalizer in the analogue domain, i.e. equipped on the analogue amp (such as bass and treble adjustment), which is usually better.

I am also using Hysolid for the main system sitting in the living room. My DAC is iFi Audio's micro iDAC2 (USB DAC) which requires the dedicated ASIO driver, 32bit for Windows PC. I do not use onboard USB ports, I recently bought a high-quality USB card which works fine and the SQ improves a...

Here is the tech note what is s-balanced and full balanced; https://ifi-audio.com/wp-content/uploads/2018/11/iFi-audio-xCAN-S_BAL-Tech-Note.pdf

GTO filter is implemented by firmware (software), not hardware.

Try it yourself. If you do not like it, just go back to the firmware w/o GTO. It is simply a taste of preference. Nothing else.

Ifi is saying that the mains (wall socket or power outlet) charge the built-in battery by which the unit is powered.

Thanks, Sebastien. That is what I thought, though my usage will be for a home audio system (not portable) since I own xDSD for portable. Micro iDAC2 is still an excellent DAC even now with an affordable price tag, while it has been discontinued.

I am also interested in this topic since current my main system is micro iDAC2 --> pro iCAN and I am curious if Neo or Diablo is clear upgrade path against micro iDAC2. I am hesitating to go to pro iDSD because of too much functional duplication with pro iCAN. I do not really need headphone...

Diablo seems already selling in Canada, though official iFi's homepage has not shown yet. https://www.electronicsforless.ca/ifi-idsd-diablo-mobile-reference-dac-headphone-amplifier-11420.html

This is great information as well as your detailed review since I own nano iUSB3.0 to feed micro iDAC2 + pro iCAN so far. Probably Neo iDSD is a right upgrade path for my chain.

Use ASIO driver; https://ifi-audio.com/firmware/windows-usb-2-0-drivers/ See also here for DSD native playback. https://ifi-audio.com/home/computer-audio-tutorial/enhanced-listening/

I think the design concept of both products is different. The micro iDSD Signature is intending to use portable, all-in-one solution, while Neo iDSD is desktop (home audio) use. I actually own micro iDAC2 which is DAC/amp combo but rather pure DAC is intended and preferably feed to an analogue...