USB sound card for audio spectrum analysis

cwtim01

Member
2012-08-11 8:14 am
Just received my Terratec Phase X24 from eBay. It does work in Windows 7 and deliver what was promised by the RMAA report.

Unlike most soundcard where the sweet spot is at -15dBFS or below, the X24 can deliver high performance at high signal level. The unit I got is giving -111.7dB THD and -100.5dB THD+N at +3dBV level :D

The X24 DAC seems to be the bottleneck here, and using a Viktor oscillator will most likely improve the figures.
 

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I think this is really ideal. Small enough to pack for the road yet having the larger input voltage range along with single and balanced io. I wish this had come out before I got the BabyFace Pro, but I still signed up for two of these anyway.

Currently redoing my test interface Jig for balanced signals. This would be interesting. I was worried that the BabyFace Pro input impedance was lower than I like; now this is out with significantly higher input impedance, I am expecting to see new data when I do interconnect measurements. Looks like I also could use more simplified Jigs with this thing.
 

1audio

Member
Paid Member
2004-03-24 5:16 am
SF Bay Area
Just received my Terratec Phase X24 from eBay. It does work in Windows 7 and deliver what was promised by the RMAA report.

Unlike most soundcard where the sweet spot is at -15dBFS or below, the X24 can deliver high performance at high signal level. The unit I got is giving -111.7dB THD and -100.5dB THD+N at +3dBV level :D

The X24 DAC seems to be the bottleneck here, and using a Viktor oscillator will most likely improve the figures.

Those are simply not available in the US. I checked ebay every way i could think of.
 
Unlike most soundcard where the sweet spot is at -15dBFS or below, the X24 can deliver high performance at high signal level. The unit I got is giving -111.7dB THD and -100.5dB THD+N at +3dBV level :D

The X24 DAC seems to be the bottleneck here, and using a Viktor oscillator will most likely improve the figures.

I snagged a Terratec Phase X24 off the big auction site too. Doing a bit of testing and it does have better performance at high signal levels. Mine does not seem to be measuring quite as good as yours cwtim01, but it is measuring a good bit better than my QA400 does. I included two screen shots. The first is loopback on the Terratec and the second is with the Terratec being fed from my Amber 3501 oscillator at approx the same level. Both are in single ended mode as my 3501 doesn't have a balanced output for the osc.
 

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cwtim01

Member
2012-08-11 8:14 am
Nice that someone else has picked the Phase X24 also. You're getting -123dB THD @3.7 dBV with your external oscillator, pretty good result I would say. It seems the X24 receiver is at the same level of the RTX analyzer (currently under group buy), but it's generator section can't keep up. It'll be interesting to see if some mods and opamp upgrade may improve the generator part.

BTW, the loopback I showed before was a balanced loopback, so we're not comparing the same thing and I'm not sure my sample is better than yours. Something I noticed and worth mentioning though:

- Do not use the external power jack if you can, the spectrum will be much cleaner. The X24 is using a AC-AC adapter for external power, but it's internal rectifier/regulator doesn't seem to be good enough. The noise floor may rise very slightly if you just rely power on the FW port, but it's much cleaner.

- Just in case, make sure you don't use the digital mixer for routing in the X24 control panel.
 
Last edited:
CWTIM01,

I tried the X24 in balanced loopback too and it was basically identical to my single ended test. I am having to use the AC wall adapter though. I only have my old Dell laptop with 4 pin firewire port so I do not have the option of supplying power via the laptop. That may be the problem as to why my loopback test is somewhat higher than yours.

Running some more tests, it seems the THD + N sweet spot with this Terratec is about 1 - 1.5dB before it hits the clipping indicator on the front of the box.