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Guide for idiot to testing ipod with RMAA needed, Brief but enough
4sure
post Aug 10 2012, 15:19
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Hi there. Can someone a little bit bother to explain (briefly) how to measure ipod etc. with RightMark Audio Analyzer?


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extrabigmehdi
post Aug 10 2012, 15:48
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From an ipod, that doesn't seem trivial. I looked at the NwAvGuy blog, and they don't seem to use that kind of test:
http://nwavguy.blogspot.com/2011/02/testing-methods.html

My guess, of how we could perform a rmaa test from an ipod:
you'd put in the ipod a lossless record of a high frequency matching the one used by the rmaa test, and then you'd connect the ipod to the line in of some soundcard.

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skamp
post Aug 10 2012, 16:22
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It is rather trivial, actually.

  • Generate a 16 bit / 44.1 kHz test signal and calibration signal .wav files with RMAA. Put those .wav files on the iPod.
  • Connect the iPod to the line input of your soundcard. Use either the headphone jack or the Line Out Dock with a special cable.
  • If you decide to use the headphone jack, you might want to measure the iPod with a "load", i.e. with headphones attached. You'll need a 3.5mm jack splitter for that. Connect the splitter to the iPod's headphone jack, plug the headphones into the splitter, as well as the 3.5mm male-male cable from your soundcard.
  • Disable all sound processing features on the iPod (EQ).
  • Set the volume on the iPod to the maximum (0 dB, I don't think it goes higher, so it shouldn't clip). Skip this if you're using the LOD.
  • Play the calibration .wav file on the iPod and record it with your soundcard, using any audio recording software (e.g. Audacity).
  • Repeat the previous step and adjust the recording volume on your soundcard until the recorded wave is close to 0 dBFS (but don't go too high and make it clip!).
  • Play the test signal on your iPod and record it with your soundcard.
  • Load the recorded test signal .wav file in RMAA (not the one on the iPod).
  • Export the results as HTML + images


This post has been edited by skamp: Aug 10 2012, 16:49


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saratoga
post Aug 10 2012, 17:21
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Yeah its simply. Just play back the RMAA test track from the ipod. But make sure you get the headphone splitter and test with your actual headphones inserted, otherwise your results will be wrong for anything but listening on powered speakers.
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xnor
post Aug 10 2012, 18:57
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I don't know if the ipod can handle 24 bit files but it'd try that over the 16 bit one. That way you're not limited by the format of the test signal (although I doubt the ipod will hit that limit).

Also, if RMAA doesn't recognize the recorded file makes sure you recorded a bit before you started playing the test signal and stopped recording a bit after the test signal was done playing. If RMAA still doesn't recognize the recorded test signal there's most likely some sample rate conversion going on.

This post has been edited by xnor: Aug 10 2012, 18:58
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Arnold B. Kruege...
post Aug 11 2012, 10:51
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QUOTE (extrabigmehdi @ Aug 10 2012, 10:48) *
From an ipod, that doesn't seem trivial. I looked at the NwAvGuy blog, and they don't seem to use that kind of test:
http://nwavguy.blogspot.com/2011/02/testing-methods.html


If memory serves, he's using Spectra Lab. Great product, costs a lot of money.

I tested a ton of equipment with Spectra in the late 90s and early 2000s. Then a really smart Russian came up with the Audio Rightmark program that basically automates what I was doing manually with Spectra. Guess what I use today? ;-)

QUOTE
My guess, of how we could perform a rmaa test from an ipod:
you'd put in the ipod a lossless record of a high frequency matching the one used by the rmaa test, and then you'd connect the ipod to the line in of some soundcard.


No, you use RMAA to make one of its test files which would be a 2-3 minute wav file, convert that into whatever the player works well with (preferably lossless) and then record the output of the player with the best computer and audio interface that you could muster. Along the way you may have to boost the amplitude of your recorded file to get it within the range Rightmark wants. You will probably have to trim it.

This post has been edited by Arnold B. Krueger: Aug 11 2012, 10:53
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4sure
post Aug 11 2012, 15:08
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Thanks to you all guys clearing the process. One last quest: Shall we have to first analyze our comp sound card with RMAA? If so, how does the RMAA-found specs of the sound card (to which I'm attaching ipod) affect this whole test? For example, if I get x% THD from the card and y% THD from ipod test, will the ipod THD be (y-x)%?

This post has been edited by 4sure: Aug 11 2012, 15:11


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saratoga
post Aug 11 2012, 15:24
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If your sound card is bad the rmaa test results will reflect the sound cards performance and not the device. Make sure your sound card is better then what you are testing, at least for the metrics you are interested.
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xnor
post Aug 11 2012, 16:28
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Lets assume both your soundcard and tested device have a THD of 0.003% (~ -90.5 dB). With a bit of math you can calculate that the resulting THD will be 0.004% (~ -87.4 dB).

If your soundcard is worse than that it will dominate the measurements. On the other hand, the better it is the less affect it will have on the measurement results.
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