Will an RS1 benefit from a low power amp, though? That’s kind of the question I have. Is there a place that exists between a $9 Lightning dongle and a $110 Liquid Spark that will actually provide a real world sound quality improvement?
The $9 dongle is surprisingly good for a lot of easy-to-drive headphones, and headphones that require more power typically call for desktop devices in the 1 or 2 watt range. Is there a benefit at 100mW, where it’s not merely academic on paper...
That "place" is being 32ohm 96dB/1mW to 99dB/1mW, smack between 300ohm, 97dB/1mW or 62ohm, 93dB/1mW and 33ohm, 117dB/1mW or 32ohm, 120dB/1mW.
On paper that means you need about 128mW to 256mW if you really want to crank it a bit without having a problem with current delivery or put you well within Class A range without switchover droops if it switches over during transients or avoid it altogether with a pure Class A amp on a desktop or you're just fully in Class B mode on a portable.
In short...1mW out of an amp with huge power capacitors is far enough from 15mW of a chip connected to USB power off a mobile phone.
...but something that is actually noticeable in real-world performance?
Here's one problem.
Regardless of what equipment is being compared there's no way I can be absolutely certain that
you or
anybody else can hear the difference.
I can hear the difference between my phone and laptop output jack, which is still around the same level of power as a USB dongle until you get to something like an Audioquest Dragonfly that will pull max power out of the USB port, and my Ibasso D-Zero driving an SR80e or even an HD600. I can still hear the difference jumping from that D-Zero to my Corda Cantate.2 on the HD600 and the SR80,
but by that point it's more of noise as the Cantate.2 beats even an amp or DAC-HPamp running on a battery when it comes to noise floor. Plus the D-Zero amp tends to be softer at the top end.
That is nowhere near any guarantee that
you will hear a difference.
And besides...at the end of it, it won't matter whether you can or can not hear a difference in performance on a range of products you have no use for as to find their existence perplexing, because you're not even interested in buying them, and as it is, have no use for them. In short...you're not the target market, partly because you don't even have anything that fits within the use case nor use that in such a situation that some would want that product for. Take that D-Zero for example - it's for getting around crappy mobile phones without getting a DAP, and works with a laptop, so even if the power is overkill the THD+N can even make a world of difference with IEMs all thanks to some really crappy phones. At the same time I wouldn't even use a dongle when walking around and just contend with its deficiencies on my IEMs, so since I'm just going to use it sitting on a desk, why then would I get a Dragonfly? Might as well get a D-Zero...which is kind of me in your position at this point since I can't comprehend why anyone would use a USB-powered device that will draw a lot of power since it relies on USB instead of its own battery). Coincidentally, that D-Zero subbed as a DAC when my old SPDIF DAC (and my CDP) broke.
Think of it another way: if you live in the city and can take the subway, you take the subway to work and then the one garage slot you have is taken up by a recreational, high power sports car or sports sedan for driving far from the city on weekends, and getting perplexed by suburbanites are driving around in a Camry with a 3.5L V6 instead of either keeping to an econobox that sips fuel around downtown areas (but also rattles when driving over freeway expansion joints, the wheel moves when a big rig blows by on the next lane, can barely get up to speed to not get rear ended by that big rig when getting up the on-ramp, etc) and that sweet Corvette that you drive. Or maybe the suburbanite has something more interesting than a Camry, but it's a 6cyl (maybe also turbocharged) small sports sedan or a bigger sport sedan with a bigger engine, but it's still perplexing why they'd get a fat car with a big engine instead of, say, your Lotus Elise or a cheaper Camry...which is more because hey maybe they need an AWD V6 or V8 biturbo or just a plain big high-revving V10 to have fun in but still be comfortable for daily driving as well as fit two more passengers in the back.
