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Need some advice to drive my akg headphones with an audio interface.

Vagalume

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Hi everyone, I am a musician and I don’t have any knowledge about impedance, voltage, sensitivity and so no. However, I can see that my old interface has some difficulties to drive my AKG702 headphones (I know I could use other headphones that I have or buy a DAC but I am not interested in both).

Besides, it is time to change my old interface, I am considering two options: the first one it is my favourite but sadly I am not sure if it can drive my loved 702 with any of its 3 heaphone output modes. The issue with the second interface is that it lacks another important feature with me and I would only buy it if the first one is not good enough.

Any help would be appreciated, I don’t want to have an interface which can’t drive comfortably my favourite cans again, I don’t want to make a wrong decision.

I can give all the info I could find about the 3 devices:



AKG 702 SPECS.
Impedance: 62ohms
Sensitivity (dB SPL/V @ 1 kHz) 105


FIRST INTERFACE SPECS
This interface brings you three different modes to use with your headphones:
MODE A Standard.
MODE A. for headphones that specify their performance at 100 dB/mW or higher.
MODE C. for headphones with a an impedance of 250 ohms or more.

Mode A specs
Frequency Response 20Hz - 20kHz +/-0.02dB
Dynamic Range (A-weighted) 112dB
THD+N (-1dBFS) (@1kHz) 0.005%
Maximum Output Level +10 dBu
Output Impedance <1 Ohms

Mode B specs
Frequency Response 20Hz - 20kHz +/-0.02dB
Dynamic Range (A-weighted) 108dB
THD+N (-1dBFS) (@1kHz) 0.001%
Maximum Output Level -6 dBu
Output Impedance <1 Ω

Mode C specs
Frequency Response 20Hz - 20kHz +/-0.02dB
Dynamic Range (A-weighted) 112dB
THD+N (-1dBFS) (@1kHz) 0.001%
Maximum Output Level +18 dBu
Output Impedance <1 ohms


SECOND INTERFACE SPECS.
maximum output level: 18.5dbu=0dbfs
thd+n @ -1dbfs (1khz): 0.0006%, -104db
dynamic range: 124db a-weighted
crosstalk: -117db @ 1khz, -101db @ 10khz
frequency response: +/- 0.2db 10hz to fs/2 (nyquist)
output impedance <50 ohms unbalanced
max level into 30r 2.63v peak, 1.87v rms, 232mw
max level into 60r: 4.28v peak, 3.03v rms, 295mw
max level into 600r: 7.91v peak, 5.6v rms, 104mw
 
Actual sensitivity for these AKGs is more like 99-100 dB / V (97-98 dB / 0 dBu). Following NwAvGuy's recommendation of 110 dB SPL (which is higher than you'd typically go for in speakers already), that translates to looking for a good 3 Vrms into 62 ohms.

What I can tell you about interface #1 is that it has a noise floor low enough for sensitive IEMs in mode B, and that it would drive vintage 600 ohm AKGs loud enough in mode C. (Also, the DAC is fine but nothing overly special, just workhorse midrange audio interface level. Probably an older design.) The specs say absolutely nothing about actual current capability, so I have absolutely no idea how loud your cans will go before clipping. You would have to look for actual measurements (or a teardown that includes a good look at the headphone amp section). Which interface has 3 headphone gain settings anyway? The designer must know a thing or two about headphones, so there is hoping that they put in enough oomph, but I don't have a crystal ball. Incomplete specs are incomplete.

Interface #2 looks like an Audient something or other, probably iD24? That would definitely do the trick.

(I know I could use other headphones that I have or buy a DAC but I am not interested in both)
There is also a third option, using an external headphone amplifier, assuming the current interface is worth the investment and its headphone output makes a decent line-out. It's a good approach for sprucing up interfaces that are current or output impedance (or noise) challenged but have decent performance otherwise.
 
Thanks for you time and detailed explanation, Steph.

About the info of the first interface (SSL12), I couldn’t find anything else in their website or user manual. The fact that it offers no detailed info about its headphone output made me suspect it wasn’t very special so I came here to confirm my suspects. And yes, the second one, as you have guessed, is an Audient id24. I guess I would have to buy the Audient, I am a little disappointed because I like the SSL12 in many ways. A pity.

 
Thanks for you time and detailed explanation, Steph.

About the info of the first interface (SSL12), I couldn’t find anything else in their website or user manual. The fact that it offers no detailed info about its headphone output made me suspect it wasn’t very special so I came here to confirm my suspects. And yes, the second one, as you have guessed, is an Audient id24. I guess I would have to buy the Audient, I am a little disappointed because I like the SSL12 in many ways. A pity.

I have a pair of AKG K712s, and 60 ohms is not too high that modern audio interfaces can't drive. You can't go wrong with the SSL audio interface... its headphone output is high current and it can easily drive your AKGs
 
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