Do Audiophiles usually keep the gain of the digital source at around 80%?

I believe the A8 supports ReplayGain, allowing you to apply it to individual tracks or entire albums. ReplayGain doesn't involve any re-encoding or lossy digital processing—it's simply like having a servant or robot adjust the playback volume for you.

@richardbrand

ReplayGain in Eversolo, WiiM or other streamers is commonly implemented via metadata (i.e., data about the audio data), not through destructive or lossy digital processing. It works by analyzing the audio file and storing the recommended gain and peak levels as metadata tags. A compatible player then reads this metadata and adjusts the playback volume accordingly. The original audio data remains intact.

... This not correct. The Eversolo doesn’t really have a preamp function, it only has digital volume control, you need analog volume control in order to be considered a preamp, and even then it would only be a passive device. You absolutely need to run the Eversolo at 100% with pass through volume control to extract maximum sound quality. 

This is absolutely incorrect statements.  A lot of misinformation floating here and people need to do their homework before writing...

The DMP-A8 has a fully balanced analog preamplifier section complete with R2R volume control and a pair each of RCA and XLR inputs. That makes it a more complete no-compromise integrated solution in which users just add power amp or active speakers and control everything from the Eversolo itself, with no outboard preamplifier needed. 

In addition, more and more players like Wiim Ultra use 32 bit for digital volume control.  Unless you attenuate volume more than, say, 50dB, you are free of negative consequence of bit-depth truncation for high-rez music listening.  There are more than enough headroom to control volume digitally with no audible degradation even down to very low levels.

You don’t necessarily need a preamp, and I don’t wish to be contentious on this subject. However, a DAC with a well-designed gain stage—like the discrete Class A output stage in Harmony Micro DAC—can drive an amplifier beautifully. I used to be in the preamp camp for a while, but after getting a quality DAC like this, I’m switching back to the “no preamp is the best preamp” camp.

Inserting a good preamp in the chain can often sweeten the sound and augment the soundstage, but I also notice a slight loss in dynamics. I have actually mitigated that through the source by adding a DDC and good cabling. I believe the source dominates the quality of the signal chain, rather than the backend. This may contradict your statement, but I am simply sharing my experience.

@sns  DMP-A8 features an R2R (resistor-to-resistor) volume control. This R2R (Resistor to Resistor) network, implemented with precision resistors and relays, is part of the DMP-A8’s fully balanced analog preamplifier section.  This says in the manual.  Where did you see that its volume control is in digital domain?  Did you actually own A8?

@devinplombier One thing we can agree on, I think, is that whether standalone or integrated to an amp or to a DAC, a preamp or preamp stage is always involved.

The quality 'gain' stage (or buffer) in Harmony micro Dac I was referring to earlier is NOT a preamp section, rather a 'voltage' gain stage serving two purposes: increase of voltage to line level and impedance matching.  It does not have the volume control to be qualified as a preamp section.  However, it drives my amp pretty well.  The 32bit digital volume control from Wiim Ultra renders no resolution loss, transparent sounding even down to low level.

at the risk of being labeled a VC snob, I am going to have to respectfully push back against the notion that a digital volume control, even a 32-bit one, is an acceptable choice in any but value-conscious devices.

I wouldn't call it snobbery, but there's definitely prejudice involved. I did a simple comparison between the digital volume control on the WiiM Ultra and the 64-step relay analog volume control on the highly praised Schiit Saga 2. At normal listening levels (60–65 dBA), the sound quality was nearly indistinguishable—both were detailed and transparent. However, at lower volumes around 45 dBA, I actually preferred the digital volume control. It delivered articulate bass and clear treble, while the analog counterpart sounded a bit muddy. You might argue that the Saga 2 is only mid-end and that a high-end preamp would perform better. But that’s precisely the point of this comparison: I was able to get better sound at low volume from a device like the WiiM Ultra, which is priced similarly to the budget-friendly Saga 2—whereas achieving the same low-volume performance with an analog preamp might require spending significantly more ($$ or even $$$).  Note that the soundstage shrinks in both scenarios—there's no clear winner in either case.