How much juice do I need?

[Wunderphones]

I recently had the opportunity to set up my dream listening room, and have thus liquidated my desktop headphone setup (the desk in question is in the listening room).

Now I want to get a device that I can use as a Roon endpoint on the move with my full-size heaphones throughout the rest of the house. I'm not really committed to a particular type of device--a portable DAC/amp that I could connect to my phone could work, as could a DAP.

My two pairs of full-size headphones have pretty similar demands, both being relatively low impedance planar models:

1. Mr. Speakers Ether C Flow 1.1: 23 ohm impedance, 92 db sensitivity
2. Hifiman 400i 2020: 35 ohm impedance, 93 db sensitivity

I gather, from reading forum posts here and elsewhere, that with headphones like these, I should actually be more concerned with current than with voltage, but it is a bit of an understatement to say that listings of the current output of various DAC/amps and DAPs are hard to find. What are the rules of thumb I want to follow when estimating whether a given device will power these sufficiently? (I think that's probably the better question than "what should I buy," but if you want to tell me that, go ahead! I use Tidal, so MQA is a big plus, and will need a 4.4mm jack.)

 

[Helicopter]

If you were shopping for a $500 desktop device I would say 4-10W for oeaks, headroom, extra headroom for EQ, and listening loudly.

Since you need to make compromises for portability I'd say 100mW... 200mW would be better though. Too bad the Hidzis players use 2.5mm balanced and the Sonys are so expensive. Not sure what to recommend. You might be better off with some easily driven headphones and a $10-30 LG Rebel phone as a DAP.

 

[DVDdoug]

I gather, from reading forum posts here and elsewhere, that with headphones like these, I should actually be more concerned with current than with voltage,

Current is a result of Voltage applied the load: Ohm's Law says Current = Voltage/Resistance. (More voltage means more current and power, and lower impedance also means more current and power.) As long at the amplifier can put-out the needed voltage and as long as the voltage doesn't drop when you connect the lower-impedance headphones, you'll get the needed current.

When no headphones are plugged-in the voltage is still present but no current flows.

Power (Watts or milliwatts) can be calculated as Voltage x Current, or as Voltage-squared/Resistance.

Apparently, planar headphones are not as efficient as regular dynamic headphones at converting electrical energy into acoustic energy.

High impedance headphones tend to be less sensitive because you're getting less power with a given voltage.