The iMac Pro generally impresses me: fast, quiet, powerful, and great screen. It’s made faster high-end macro photography editing by at least 3 hours per image. Not bad.
It’s audio audio output is a mixed bag. Impressive points: low noise floor, low amp noise, and extremely good current to volume ratio. It hisses a bit more than an iPhone SE when driving sensitive earphones like Campfire Audio’s Comet. It carries loaded signals well and generally sounds good. But - and I assume this is true of all late-production iMacs - its signal is both weaker (voltage/volume) and measures worse under the same benchmark than a 2012 iMac. The older iMac has less signal noise, greater dynamic range, and better stereo separation.
The iMac Pro loses points when driving loaded signals to headphones, though the skew is paltry compared to many DACs I’ve used.
Of course, absolute performance really only really matters when the analogue output is being hooked up to an external amp. Low noise and distortion ensure cleaner downstream sound. But, at normal listening levels, the iMac spits a clean, slightly warm, and muscly signal. While being bested in most benchmarks by the likes of NextDrive’s Spectra seres (both the original Spectra and Spectra X), it keeps jitter, THD, and IMD lower at max volume. Of course, that max volume significantly weaker than Spectra’s. It is also lower than a 2012 iMac, meaning it won’t power your DT880 and HD600 as well.
One step forward, one step backward.
NL - no load
SM2 - Earsonics SM2
ES7 - Audio Technica ES7
DT880 - Beyerdynamic DT880/600
24-bit single ended @+0dB - all targets
24-bit single ended @+0dB - NL summary
Rarely do Apple take serious steps back. The iMac Pro’s internal amp is less noisy than the one in my previous iMac’s, but overall it isn’t as good. That the better one is five years older is quite the indictment.