Question 1

Nos = no over sampling and os = over sampling?  if so, how much over sampling?

Accepted Answer

The EF400 uses HiFimans 'himalaya' R2R DAC which is a custom resistive-ladder chip using individual precision resistors to perform the D->A conversions. Because Dr Bian's decoding arrays are inherently very accurate, they don't benefit much from oversampling unless the digital source is very poor and by not oversampling, its analog output has no sonic artifacts left over from an oversampling stage that must be filtered away.

So I think that the himalaya's oversampling mode is very low like 2 or 4X - HiFiman doesn't disclose their sampling rates, but it doesn't matter - unlike delta-sigma DACs, that must oversample to minimize the distortions inherent in their D->A conversion and the digital filtering required to reduce them to acceptable levels - R2R DACs oversample to increase their conversion accuracy and dynamic range and require little or no post-processing of their analog output.

I've had this EF400 for about a year, and its been flawless, it drives power-hungry planars like HiFiman Edition XS, or Monoprice M1070 with control, authority, and revealing detail. Conversely, switch to its low-output range, and sensitive dynamic headphones like the HiFiman HE-R9, or Harmonicdyne Poseidons are presented against an utterly 'black,' noiseless background.

Yeah, 500 dollars is a pretty stiff hit "Just to listen to headphones..." but I believe that the EF400 is pretty much the end game for any setup costing less than six figures.

Cheers
Jim

Question 2

can it be used as preamp fot active speakers and control the volume from both?

Accepted Answer

No. The rca jacks are fixed volume and the volume knob on the front only controls the headphone jacks.

Question 3

does this dac/amp works with Playstation 5?

Accepted Answer

As long as your PS5 has a USB out, which I think it does, the amp should work. The EF-400 only takes USB-B or USB-C, no optical or USB-A. So be aware of that.

Question 4

Will this power the Hedd Heddphone or any other hard to power Headphone with enough power?

Accepted Answer

I think it has enough power for planar. However, it may not listened good for some headphones, such as LCD-X. You can try it

ASIN	B0B1MGWGKZ
Best Sellers Rank	#97,587 in Electronics ( See Top 100 in Electronics ) #162 in Headphone Amps
Brand Name	HIFIMAN
Customer Reviews	4.3 4.3 out of 5 stars (90)
Global Trade Identification Number	06925624202408
Included Components	Power cable
Item Dimensions	24.6 x 22.8 x 6.1 centimeters
Item Type Name	HIFIMAN EF400
Item Weight	3.08 Kilograms
Manufacturer	HIFIMAN
Maximum Output Power	4.4W
Maximum Supply Voltage	110 Volts
Minimum Supply Voltage	110 Volts
Model	EF400
Mounting Type	freestanding
Number of Channels	4
Number of Items	1
Number of Packs	1
Output Power	4.4 Watts
Part Number	EF400
Unit Count	1 Count
Voltage	220 Volts

HIFIMAN EF400 DAC Balanced Desktop Headphones and Amplifier with Himalaya R2R DAC, 3.5/4.4/6.35mm Output for Home Audio, Silver

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