Going Battery Powered

first,to the OP, Great! insightful question. And, in both theory and reality, yes.
now, practice is the hard part.  Back in the 80s, a friend and ex business partner suggested and ran, so "battery parties" where 8+ folks would get together and donate, for a while, car batteries so we could get + and - 48 Vdc with stupid hgih current (commenting on a sub thread above).
Sound: superb. Practicality: Zero.  But that was 40 year ago.
Today, for low power draw products, Lithium Ion batteries are a great way to go - but probably you will have to roll your own.  Charging is nto as simple as hooking p 12 (or whatever) volts.
 It is quieter. "blacker" as one put it. And more nuanced and dynamic.  Compared to a really good power supply, its very subtle. Compared ot the typical one, well.... your definition of typical may stray from mine. I'm not impressed.  Everything I build a power supply for gets way better.  Off topic note: wait for my rant on an Intel NUC as a ROON ROCK server, and the lessons in reality i learned.... but i digress.
It will be a project.  but the end goal may prove worthwhile.
G

I use batteries for my DIY phono/pre. It’s black, and I would not go back. I use 120VAC power for the DIY amplifiers with very fast and very quiet bridge rectifiers and LCLCLC filter circuit. A hundred kilograms of inductors and a Farad of capacitance. Not cheap.

An AC power supply typically is made from a step-down transformer and a rectifier, at which point the power peaks at nearly 1.5x the voltage of the transformer's secondary, and sags to 0. 120 times per second. Obviously this is pretty lousy power, so it must be smoothed with reactance (inductance and capacitance).

The best AC power supplies follow the rectifier with an inductor (L) followed by a capacitor (C), with two or three stages of LC. These serve to smooth the voltage variation, known as the ’ripple voltage’. Lower is better.

It costs an arm and a leg to get ripple voltage down to 1ppm, which corresponds to .012mV. Not even the worst battery is that noisy. Which is why it’s better to power directly from batteries than to regenerate and then go through the transformer and rectifier and LC filters to achieve an inferior result.

The downside is that batteries store energy and can deliver it pretty fast, so it’s wise to have them fused. And have quality connectors that can’t be pulled apart by accident.

Just my views. YMMV

jzzmusician
I'm a dummy; what does, "PPT," stuff mean?

Just another BS voodoo snake oil product like ($1) $150! ac mains fuses, but this ones a $300! contact cleaner
https://perfectpathtechnologies.com/product/total-contact/

Electronic engineers use as good if not better one for $22, but it's not got an "audio" snake oil signature to it.
https://www.ebay.com.au/itm/DeoxIT-Mini-Gold-spray-GN5MS-15-14g/401602406187?epid=6024006287&hash=item5d815e672b:g:954AAOSwgHpa28-g&frcectupt=true

Cheers George 
  

Just to mention there is no power or dynamics issue with low-powered portable CD players. That’s actually one really big advantage of low mass systems, the ability of teeny tiny AA or AAA Lithium batteries to provide full dynamic range without constricting dynamics. You just can’t use certain headphones like some Sennheisers. I use a vintage SONY MDR-v700 and Grados and others, no problemo.