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RMAA results for iPod Classic, Galaxy Nexus, FiiO E7
skamp
post Apr 26 2012, 20:58
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Here are the RMAA results for the iPod Classic (2009), the Samsung Galaxy Nexus, and the FiiO E7. The iPod was tested via it's Line Out Dock, as well as its headphone out, unloaded, and loaded with Sony MDR-XB700 headphones (24 ohms). The Galaxy Nexus and E7 were tested via their headphone out, loaded and unloaded. Here's a comparison between the 3, loaded with the headphones.

Audiophiles always say that the iPod's LOD outputs a "cleaner" signal than its headphone out; if I'm reading the values and graphs right, that seems correct. I couldn't say whether the difference is audible; one would have to also test the external headphone amplifier that would be connected to the LOD.

Overall the E7 seems superior, while the iPod is a pretty close second in some aspects, especially if you consider the LOD results. Of note is the significantly worse stereo crosstalk result from the Galaxy Nexus.

Edit: I used an old laptop for the recordings. I'm considering investing in a decent USB device. If I do get one, I'll run RMAA again.

This post has been edited by skamp: Apr 26 2012, 21:09


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saratoga
post Apr 26 2012, 21:29
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You said in the other thread that you've got the volume cap on your ipod. If so, you need to either remove that so that you can use the full dynamic range of the ipod, or else set the level on the other players to be identical to the ipod. Otherwise you're basically handicapping the ipod by not letting the DAC use its full SNR.

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skamp
post Apr 26 2012, 21:37
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The volume cap can't be removed. How does the volume of the recording affect the results? I didn't match the volumes. Are my results useless?

Here's some better results. Obviously my SNR and noise measurements are completely off. I'll run a corrected test later.

This post has been edited by skamp: Apr 26 2012, 21:54


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saratoga
post Apr 26 2012, 21:52
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QUOTE (skamp @ Apr 26 2012, 16:37) *
The volume cap can't be removed.


Sure it can. I know for a fact that we don't implement it in rockbox, since i reviewed some of the patches for the ipod 6G's sound driver smile.gif

QUOTE (skamp @ Apr 26 2012, 16:37) *
How does the volume of the recording affect the results? I didn't match the volumes. Are my results useless?


The frequency response will be unaffected, but it will probably make everything else look worse by about however many dB its capped. Both because they will be worse, and because your sound card will probably struggle to record such weak signals without introducing more noise.

That said,

QUOTE (skamp @ Apr 26 2012, 16:37) *


.. those are a lot better. I tend to think that the system you recorded with actually has a higher noise floor then the devices you were testing so maybe the SNR results aren't going to be right regardless. Still, good to know all of the devices you tested have very high SNR smile.gif
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skamp
post Apr 26 2012, 22:16
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Thanks. I guess I'll just suck it up and buy a better recording device. I like the Edirol UA-4FX.


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skamp
post Apr 27 2012, 09:41
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Well, I dusted off my old PC and tried three different PCI sound cards that were lying in a box. I got much better results with the Terratec Aureon Sky 5.1 (which wasn't the most expensive of the bunch). I measured a DR of about 92 dB. The iPod LOD is actually the winner with that setup, but all devices fared quite well (see individual results).


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Arnold B. Kruege...
post Apr 27 2012, 12:16
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QUOTE (skamp @ Apr 27 2012, 04:41) *
Well, I dusted off my old PC and tried three different PCI sound cards that were lying in a box. I got much better results with the Terratec Aureon Sky 5.1 (which wasn't the most expensive of the bunch). I measured a DR of about 92 dB. The iPod LOD is actually the winner with that setup, but all devices fared quite well (see individual results).


Which kinda proves a point I've been trying to make with some success for years, and that building a good potentially sonically transparent audio interface isn't exactly rocket science and doesn't take a NASA-sized budget.

On another forum, I recently saw a poster who just invested in this combo:

"I have just begun to convert some LPs to 192/24 digital files using PureVinyl and a TC Impact Twin." The interface runs close to $400 and the software runs about $130. I can see exactly what they offer as compared to simpler approaches, such as the ART USB Phono Plus Interface and Audacity, but the perceived need for all of these sound-modifying tools sort of shoots holes in the idea that the LP sounds superior all by itself. ;-)
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skamp
post Apr 27 2012, 12:30
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And, lo and behold, my wonderful Asus N75SF laptop with "Audio by Bang & Olufsen ICEpower". Seems legit!


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stephan_g
post Apr 29 2012, 21:28
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QUOTE (skamp @ Apr 27 2012, 12:30) *
And, lo and behold, my wonderful Asus N75SF laptop with "Audio by Bang & Olufsen ICEpower". Seems legit!

Looks like you should inspect that one for any misimprovements present in the processing chain. Its sound implementation does not seem to be that great, but there is definitely something else going on that dominates the results. I'd say there's EQ and dynamic compression in use, presumably for better speaker audio. ICEpower would be referring to Class-D speaker amps.

BTW, measuring DAPs at anything else than 44.1 kHz is a potentially risky business. At least keep in mind that sample rate does matter.

I still have two of the aforementioned Terratec cards in use. As you found out, they are quite flexible when it comes to recording levels. They apparently were a co-development with ESI/Audiotrak at the time. I'd need to reverse engineer the headphone amp at some point, which I am told uses a Class B buffer (I never liked the result with anything less than 300 ohms much, though according to measurements coupling caps may be the bigger issue).

This post has been edited by stephan_g: Apr 29 2012, 21:36
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saratoga
post Apr 30 2012, 17:06
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Could you put those galaxy nexus results back up? I wanted to look at them again, they were pretty interesting.
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skamp
post Apr 30 2012, 19:00
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I deleted the old results, there were obviously off. I also noticed that I fucked up the links in my previous post. Here's the directory, with the Galaxy Nexus and the comparison of all three devices.


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saratoga
post Apr 30 2012, 19:02
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What happened with the frequency response on the Galaxy Nexus? I thought it was flat the other day? Or am I confused?

Edit: Also, were the previous results for the QC15s as well? Those are amplified, so they're basically the same as having no load at all.

This post has been edited by saratoga: Apr 30 2012, 19:03
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skamp
post Apr 30 2012, 19:09
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The GN always had a slight treble roll-off. I tested with the QC15 because that's what I use. I'll post results with regular headphones soon.


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saratoga
post Apr 30 2012, 19:40
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You must be right. I'm probably confusing things.
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skamp
post Apr 30 2012, 20:59
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Results with Denon AH-D1100 headphones (32 ohms) and with Denon AH-D2000 headphones (25 ohms).


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skamp
post May 2 2012, 11:21
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I installed Rockbox on my iPod last night. I updated the comparison with measurements for the rockboxed iPod. Without the volume cap, DR went up quite a bit!


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nevermind
post May 4 2012, 03:44
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Those measurements look a bit strange for the ipod (in headphones), I mean the lobes around the 1kHz sine wave. Were you using it plugged into a power adapter? A smps supply could cause that. They dissapear on the rockbox version which I think is interesting. It would be good to find out why.
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skamp
post May 4 2012, 10:12
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All tests were run on battery. Note that the lobes disappear with the LOD and stock firmware too. The big difference is the maximum volume. The stock firmware suffers from a substancial volume cap (6-10 dB I think) on the headphone out, which neither the LOD with stock FW nor Rockbox have.


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stephan_g
post May 5 2012, 12:51
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These lobes seem to be an artifact introduced by RMAA when input level is low. It's a little cranky at times (and sometimes, more than just a little).
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Arnold B. Kruege...
post May 8 2012, 13:39
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QUOTE (nevermind @ May 3 2012, 22:44) *
Those measurements look a bit strange for the ipod (in headphones), I mean the lobes around the 1kHz sine wave. Were you using it plugged into a power adapter? A smps supply could cause that. They dissapear on the rockbox version which I think is interesting. It would be good to find out why.


Those kinds of "lobes" are usually windowing artifacts. IOW, the data and the time window that was applied to it were mismatched.
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skamp
post Dec 7 2012, 09:46
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I got an EMU 0204 USB and made new measurements. I think I need a better stereo splitter cable for loaded tests, because the stereo crosstalk values are suspiciously high. I even managed to squeeze out 7 more decibels in one case just by wiggling the jack :-/


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Arnold B. Kruege...
post Dec 7 2012, 15:05
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QUOTE (skamp @ Dec 7 2012, 03:46) *
I got an EMU 0204 USB and made new measurements. I think I need a better stereo splitter cable for loaded tests, because the stereo crosstalk values are suspiciously high. I even managed to squeeze out 7 more decibels in one case just by wiggling the jack :-/


Wise man makes his own lab cables.
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skamp
post Dec 8 2012, 23:10
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On second thought, I'm not sure my stereo splitter cable is to blame. When connected only to the EMU's line-in, without headphones attached, I get crosstalk values below -90 dB. I've also found other measurements of the Clip+ on the web that match mine, so I guess that high stereo crosstalk value is pretty much accurate. It's ABXable on material with content in one channel and silence in the other.


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saratoga
post Dec 8 2012, 23:33
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Crosstalk depends on current, so if you drive a high impedance source you won't see much, if any, crosstalk. But once the current ramps up you'll see a lot more of it.
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IgorC
post Dec 9 2012, 04:30
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Skamp,

Interesting measurements. I'm very surprised how EMU 0204 performs well comparing to O2 DAC without load, but not so great with your low impedance D2000 (25 Ω). EMU performs weird and that isn't surpise as it wasn't designed for low impedance phones. Its output impedance is 22 Ω. However it should performs well with high impedance phones.

I have similar EMU Pre Tracker USB and use it with HD650 and HD800 ( variable impedance, >325 Ω; ) . Considering the main rule of thumb (nwavguy's) Zphones/8 EMU USB interfaces (22 Ω, Zo) should drive 250 Ω and higher impedance phones without any issue.


Shortly, it will be interesting to see your measurements with O2 and EMU 0204 with 300 Ω phones.
I'm not sure it will be enough correct to use variable resistor (potentiometer) as dummy load because an impedance of high-z phones is actually variable per frequency (see the previos graph). One way around is to use quite simple filters RLC for more realistic simulation of phones as a load, that shouldn't be difficult. Or just get a real 250-300 Ω phones. smile.gif

BTW, as I have already mention to You on irc channel about my impressions of E17. Mmm, I prefer EMU Pre Tracker after all. Simply, it's cleaner. So I suspect that EMU interfaces could be comparable with state of art O2 DAC/AMP when used with high-z phones.
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