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pico vs predator, real measurements


kevin gilmore

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The Pico's graphs just look much cleaner overall in terms of noise floor, etc. Distortion figures from RMAA should be viewed as relative and not absolute values in my opinion. RMAA has a reputation for producing distortion numbers that aren't really believable.

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the Predator, while obviously outclassed by the Pico, in that regard, has reasonably good distortion numbers, i think.

Really? The crosstalk is interesting from the standpoint of rising with lower frequency; contrary to what is often seen (although probably due in part to the very low feedback resistors used). However, I think the distortion graphs are both more interesting and more meaningful from the standpoint of performance. That is a lot of IM distortion, and that's at nearly full scale with a stable waveform. On actual music, it's probably even worse. Distortion products at nearly -80dB with a ton of odd and high order junk along with noise is rather unimpressive. In person, the story wasn't much different (to me, anyhow).

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No kidding, this is the first time I remember seeing crosstalk figures get significantly worse at low frequencies.

Actually this is exactly what you would expect from a tle2426 (or compatible)

rail splitter that has to fight a low impedance load. Ray decided to seriously lower the values

of all the feedback resistors on the opamp such that at medium and high gain positions each

channel puts about 120 ohms of internal load to ground. That is 60 ohms that the rail splitter

has to drive before you actually add any headpones. So without any tantalum low impedance caps

on the output of the rail splitter where they would actually do some good, the output of the rail splitter is

going to sap up some of that seperation.

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I'm not sure why the Predator has both 60 and 120Hz residuals. The Predator's graphs don't look that bad on their own (other than the crosstalk one which is really bad). It's when you see the Pico's superimposed that it starts to look bad.

I always wanted to know what causes this (for the Predator... this is the IMD graph... all the squiggly crap). Intuition tells me this is the rails being modulated...:

[img width=150 height=93 alt=imd1]http://www.head-case.org/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=1279&g2_serialNumber=2&g2_GALLERYSID=3b85edc3f3e17fc5e8b25ff2ef57eac4

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I always wanted to know what causes this (for the Predator... this is the IMD graph... all the squiggly crap). Intuition tells me this is the rails being modulated...:

[img width=150 height=93 alt=imd1]http://www.head-case.org/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=1279&g2_serialNumber=2&g2_GALLERYSID=3b85edc3f3e17fc5e8b25ff2ef57eac4

Looks like part digital-side stuff to me, and part analog as well. Poor filtering/noise shaping and perhaps a sloppy modulator on the 2704 coupled with the peculiar aspects of the Predator design. You can see the digital-domain stuff in the Alien DAC RMAA as well - http://www.amb.org/rmaa/AlienDAC_16b_44k_battpwr_transit_20070420.htm. However, the Predator's results are still worse.

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Dac's both powered from the usb port. Both units run from batteries to avoid any possible

ground loops. Same intel based computer used for both.

I think i know what all the IMD crap is on the predator, but until i get some time to test and

verify, i won't say anything. Lets not forget that jude absolutely loves the predator. Can anyone

continue to trust jude's recommendations at this point? Slightly biased maybe, no never...

I think it is the same problem where the predator makes lots of hiss on some laptops...

All i have to say is Induced Harmonic Compensation. Yeah, that's it... Ray is copying Rudistor.

Truely classic.

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