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Topic: U7 vs. Omni driving HD600 (Read 8498 times) previous topic - next topic
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U7 vs. Omni driving HD600

Reply #1
Added a test of my portable players (Nokia 311 phone + RB'ed sansa clip+) driving HD600, recorded in a similar way (using Omni's line-in, but on my main PC instead of the laptop). I had to record at 48/24 in a separate editor, then convert to 44/16 (using SoX), then analyze WAV in RMAA. Omni seems to support only 48kHz recording natively and everything else is resampled using a low-order anti-aliasing filter, leading to a HF roll-off starting at 15kHz.

U7 vs. Omni driving HD600

Reply #2
Rightmark test - 24/96

Code: [Select]
Frequency response (from 40 Hz to 15 kHz), dB    +0.06, -0.01 Excellent

Noise level, dB (A)    -108.9 Excellent

Dynamic range, dB (A)     109.3 Excellent

THD, %     0.0038  Very good

THD + Noise, dB (A)    -86.1 Good

IMD + Noise, %     0.0072 Excellent

Stereo crosstalk, dB     -6.4 Very poor

IMD at 10 kHz, %     0.011 Very good

General performance       Good


[attachment=8118:_MME__Xo..._U7_2496.htm]

[attachment=8114:thd.png]

[attachment=8117:fr.png]

[attachment=8116:noise.png]



U7 vs. Omni driving HD600

Reply #4
This might shed some light:

Rightmark of Xonar U7 output driving the line inputs of a M-Audio Fasttrack Pro

Code: [Select]
Frequency response (from 40 Hz to 15 kHz), dB    +0.16, +0.05 Excellent
Noise level, dB (A)    -103.9 Excellent
Dynamic range, dB (A)     104.0 Excellent
THD, %    0.0022 Excellent
THD + Noise, dB (A)    -87.8 Good
IMD + Noise, %     0.0043 Excellent
Stereo crosstalk, dB     -101.5 Excellent
IMD at 10 kHz, %     0.0038 Excellent
General performance      
Very good


Frequency response
[attachment=8119:fr.png]

THD
[attachment=8120:thd.png]

Dynamic range
[attachment=8121:dynamics.png]

Stereo crosstalk
[attachment=8122:cross.png]

U7 vs. Omni driving HD600

Reply #5
Xonar U7 has line output on the back (cinch), which I did not test. That's likely what gives those excellent numbers that Arnold posted.

I tested U7's headphone output located on the front side, loaded with HD600 as this was my typical use case. I do not imply that U7's DAC is bad. But it is a waste when the signal goes through such a mediocre headphone amp. Or my measurement was flawed somehow.

U7 vs. Omni driving HD600

Reply #6
Xonar U7 has line output on the back (cinch), which I did not test. That's likely what gives those excellent numbers that Arnold posted.

I tested U7's headphone output located on the front side, loaded with HD600 as this was my typical use case. I do not imply that U7's DAC is bad. But it is a waste when the signal goes through such a mediocre headphone amp. Or my measurement was flawed somehow.


I measured the output impedance of my Xonar U7's headphone jack and obtained 17 ohms @ 1 KHz. Not that different the rumored 15 ohms.

U7 vs. Omni driving HD600

Reply #7
I meant mediocre with respect to noise and L/R cross-talk. The output impedance does not matter much when driving 300 Ohm headphones (unless it is in hundreds of Ohms or more).

How did you measure the output impedance?

U7 vs. Omni driving HD600

Reply #8
I meant mediocre with respect to noise and L/R cross-talk. The output impedance does not matter much when driving 300 Ohm headphones (unless it is in hundreds of Ohms or more).

How did you measure the output impedance?


Code: [Select]
(1) Y connector plugs into headphone jack of audio interface headphone jack
(2) Loop headphone output to input of audio interface for recording.
(3) Play 1 KHz tone and record it with recording audio interface ensuring that second jack on Y connector is open. Adjust levels for about -3 dB FS, and negligible distortion of any kind.
(4) Plug test jig composed of 2 each 15 ohm resistors attached to a 3.5 mm headphone plug into second jack on Y connector. Observe nominal voltage drop and continuation of undistorted operation.
(5) Again Play 1 KHz tone and record it using recording audio interface with with second jack on  Y connector loaded by resistor jig
(6) Examine recording, carefully measuring amplitude of each of the two recordings in arbitrary linear units.  If only dB are available, convert DB to linear units.
(7) Plug two amplitudes and test jig resistance into spread sheet, obtain results.  The equation cell in column E is: +(D5*B5/C5)-D5  . Column B is VOpen, column C is VLoad, and  column D  is RLoad


My calculations suggest that a 17 ohm source impedance may be a concern with low impedance headphones. I use AT ATH M50s on that interface and I'm going to scout up a second Topping NX-1 that is someplace in the house.  If I was using headphones with impedance in the 100s of ohms, then ithe 17 ohms would be less of a concern.

The maximum dB variation possible with a pair of headphones due to source impedance is: +20 * Log10 ( (Z Headphones + Z Source) /  Z Headphones). If the headphones impedance curve does not experience much variation over the audible range then this estimate is pessimistic.

U7 vs. Omni driving HD600

Reply #9
Based on the advice of stephan_g in the main thread, I did a Xonar U7 loopback test using the mic/line in jack of U7. It made a huge difference and basically proved that my initial setup was flawed (ground loop between U7 and Omi).

The output of Xonar U7 is simply excellent when driving HD600.

U7 vs. Omni driving HD600

Reply #10
Based on the advice of stephan_g in the main thread, I did a Xonar U7 loopback test using the mic/line in jack of U7. It made a huge difference and basically proved that my initial setup was flawed (ground loop between U7 and Omi).

The output of Xonar U7 is simply excellent when driving HD600.


Given their impedance:

> 300 ohms

Head Fi HD 600 review


The 17 ohms series impedance of the HD600s should not cause many audible problems.

 

U7 vs. Omni driving HD600

Reply #11
I did a low-impedance test (IE4 - 16 Ohm and HD518 - 50 Ohm) on the devices. I set the volume to a lower level than for HD600 to prevent permanent damage to the headphones.
The end result is that Omni seems to have a "harder" amplifier. U7 did somewhat bad on IE4 (3dB dip in sub-bass).

 
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