Are streamers digitally enhanced?

I think that there are manufacturers who work to reveal and others who work to enhance. My guess would be that the better streamer manufacturers seek to reveal.

“Are streamers digitally enhanced?”

In simple terms - YES!  

“But what do we know about how streamers or DACs are processing the signal? Is the goal purity or beauty?”

The answer lies in the intersection of engineering, philosophy, and subjectivity in audio. That’s why high end streamers like Pulse embodies their designer’s intention and vision for listener’s values.

Folks like your engineer friend often approaching it from a strictly data-transfer mindset, not an audio-performance perspective. Offering an explanation to a skeptic is like debating color depth with someone looking at a JPEG on a CRT monitor.

That said, for the rare skeptic who’s open-minded, one well-controlled listening session can say more than any technical spec sheet. Once someone hears how a streamer like the Pulse can open up spatial and harmonic information without adding glare or artificial edge, it’s hard to go back. 

I don't see how a streamer could possibly alter the harmonics or tonality/tonal balance of an audio system. It is only the apps loaded into streamers that could possibly affect one of these two parameters of sound quality, music players such as Roon, Qobuz, Tidal, etc. and DSP engines.  To claim otherwise  is arguing that digital packets of 0 and 1's have inherent tonality/ timbre. I  also don't  see how any music player app or dsp engine can change timbre, timbre/harmonics live solely in the analog realm. On the other hand I do agree the apps and dsp engines could change the tonal balance.

Streamers sole impacts are in resolution, transparency and presentation, this why minimizing noise and providing highest quality clocking is so important. When people are claiming their streamer adds some character to the sound they are conflating the contributions of other parts of their audio system with the streamer. A high quality streamer simply allows the 'color' of the rest of the system to shine through. The color, harmonic texture comes solely from the analog components of system, the only digital component that can alter this is the analog output stage in a dac. No network or digital data processing component has a 'sound.'

...'digitally enhanced'....
'Ell, I'm "D E'd"....

A pacemaker/defib in my chest, and I wear aids in my ears....

Ask spouse, she'll tell you I'm starting to 'talk' like R2D2.....

I agree with your studio guy. If there is a difference in sound with a well engineered streamer, it is being deliberately introduced.

From Chat GPT

If the streamer outputs bit-perfect data and doesn't introduce jitter beyond the DAC's rejection capabilities, there should be no audible difference.

Most well-engineered DACs (especially those with good jitter rejection and galvanic isolation) will perform identically regardless of whether they're fed by a Raspberry Pi, a $100 streamer, or a $5,000 one.

In blind tests, assuming a bit-perfect, clean digital output and a competent DAC, streamers do not impact audio quality. Differences reported are likely due to implementation flaws, system noise, or psychological bias.