[jklimek]

I've purchased a Qudelix 5K DAC/AMP which has the following specifications:

• 3.5mm (unbalanced) - 2 V RMS - 80 mW per channel
• 2.5mm (balanced) - 4 V RMS - 240 mW per channel

...and the Beyerdynamic DT 1990 Pro:

• 250 ohm
• Nominal - 102 dB SPL (1 mW / 500Hz)
• Max - 125 dB SPL (200 mW / 500 Hz)

I'm using this headphone calculator with these settings:

• Headphone Sensitivity: 102db(1mw)
• Headphone Impedance: 250 ohm
• Headphone Loudness: 110 dB

It returns the following chart:

• REQUIRED POWER: 6.31 mw
• REQUIRED VOLTAGE: 1.26 RMS (V)
• REQUIRED CURRENT: 5.0 RMS (mA)

Shouldn't the Qudelix have plenty of power? I've raised the volume to max (on the source and Qudelix) but it's not loud enough.

EDIT: It looks like if I disable EQ, enable high power, and use +6 dB volume it's acceptable but that's pushing this thing to the max and even then it's just barely acceptable.

 

[dunring]

It needs more than the 2v on the single ended plug your using. I've had them a few times and 1 watt into 32 ohm on the single end adapter works really well. A used JDS Atom amp is inexpensive and sounds great with those.

 

[Claypole]

The 80mW per channel quoted will probably be measured with 32 ohm headphones, at 250 ohms it may well be considerably less…

 

[VNandor]

The calculations are correct. The maximum level you can get out from your qudelix with the DT1990 is around 114dB SPL. In order to achieve that, you would have to make sure the qudelix outputs as much power/voltage as it can (enabling high gain and +6dB, disabling EQ as you already noted) and turning the volume all the way up and then using test tones instead of music because max SPL is tested with more or less standard tones, not music.

The SPL you are going to hear with music depends on the specific music you are listening to. It could be around 85-90dB SPL on average as long as you listen to traditionally high dynamic range music such as jazz or classical even with all the settings maxed out. If you listen to pop and edm instead, you would get something like 100-105dB SPL with all the settings maxed out. To me personally, 90dB SPL sounds loud, and 95dB SPL is borderline uncomfortable and 100dB SPL is definitely uncomfortable.

If you listen to quieter music in general, want to use EQ, want to use low gain, don't want to turn the volume all the way and still want to reach loud/uncomfortable volume levels you'll need more power than what the qudelix provides to the DT1990.