A few years ago I blogged about this: http://mclements.net/blogWP/index.php/2016/09/13/a-cheap-audiophile-headphone-system/

Technology marches on so it needs an update.

Here’s a cheap audiophile quality sound system:

• A DAC + headphone amp that accepts USB input.
• A decent set of headphones.

How is this better than before? It’s less expensive and more flexible. A DAC accepting USB input can be used with any computer: laptop or desktop, mac, Windows or Linux. No drivers needed.

You can get separate DAC and amp, or (even better) a single device having DAC and headphone amp. Such a device often has line level outputs and can be used as a preamp too. Like the Schiit Asgard with the ESS9028 DAC card. Simplicity at its finest: a single box is all you need.

Even better, the Asgard accepts analog inputs too. If your phone has a headphone jack, you can set it to max volume and plug it into the Asgard’s line-level inputs. Then use the Asgard (and its volume control) to drive any headphone on the planet. If not, just use an OTG USB cable to plug your phone into the Asgard’s digital input. That should provide even better sound quality, as the Asgard’s DAC is probably better than the one in your phone.