# iPhone 3GS unloaded headphone out measurements



## t3sn4f2 (Jan 3, 2007)

iPhone 3GS HEADPHONE out measurements (2Kohm load):

Headphone out set to MAX, volume limiter turned off, Airplane mode off, screen on, 3G enabled, wifi enabled, bluetooth enable, charging of USB/wall plug.

Software used is Rightmark Audio Analyzer.

First a perfect test result for a 16bit/44kHz file (ie ANY track/file you play on your head unit). Can't be better then this, mathematically limited:










Then as a reference. A loop back test result of the sound card used to make the measurement through it's input (EMU-0404PCI). Basically you take the output from the card and hooked up to the inputs. Then run a _loop back_ test to create a baseline. As long as its better then the device being test the result will be accurate: 2 volts RMS










iPhone:
(Approximately 1 volt RMS out from the headphone)










Results are normalized to compensate for output voltage differences.


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## t3sn4f2 (Jan 3, 2007)

A second opinion.....

Apple iPhone 3GS review: Same clothes, new feel - GSMArena.com


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## t3sn4f2 (Jan 3, 2007)

Now a line out test using a BMW X5's line out dock adapter. Same testing conditions. 










If you don't mind the slight rise in swept IMD then the headphone out looks to be a better choice since not only does it has a couple of dB better noise performance but it also has a couple dB stronger output (ie .25 volts RMS).

Note: The BMW LOD could have a built in attenuator that matches the universal AUX input's sensitivity that that mini jack plugs into. So your iPod is not louder then the CD player in the car and/or you don't have to adjust the head unit to make them equally loud. Other LOD's brands _might_ give a slightly higher line out voltage, but that is just an assumption.


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## t3sn4f2 (Jan 3, 2007)

Update:

Don't why I didn't try this earlier but I increased the bit depth of the recording sound card to increase its performance way past what a CD file could perform. Now the results are what the iPhone really is without a limited resolution device measuring it.











A. This is the new iPhone 3GS headphone output measurements, same testing conditions except with the increased recording resolution. Notice the drop in noise floor. 

B. This is the new EMU0404PCI 16-Bit 44kHz analog loop back baseline. It's good to see that this cards analog out performance is truly by all means equal to a digital output. This measurement was taken with a $5 Hosa 10 ft length of RCA.  

C. This is a perfect 16-Bit 44kHz test result (same as a digital SPDIF output). 

D. This is a 24-Bit 44kHz ANALOG loop back test to show the inputs maximum performance when not limited by a CD file's resolution.


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## stalintc (Dec 6, 2007)

Good objective info, thanks!


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## rommelrommel (Apr 11, 2007)

Cool thread, we need more of these. Thanks for the effort.


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## t3sn4f2 (Jan 3, 2007)

You're welcome guys, glad I could contribute.


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## Yuck. (Dec 28, 2009)

I'm kind of a noob, and I'm a little confused, are you basically saying that going through a docking cable on a 3GS will result in a very small difference in SQ vs. going through the headphone jack with a mini-jack cable?


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## t3sn4f2 (Jan 3, 2007)

Yuck. said:


> I'm kind of a noob, and I'm a little confused, are you basically saying that going through a docking cable on a 3GS will result in a very small difference in SQ vs. going through the headphone jack with a mini-jack cable?


That's what the data shows.


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## Yuck. (Dec 28, 2009)

wow, pretty amazing if you think about it, is there any amount of data that is lost in the translation so to speak? This presents me with an interesting situation for me because I'm getting my 9987 installed and I was gonna get the kce 422i for $30 or something similar that's compatible, but now I've got to use the stock AUX input...which is disabled with a 'normal' installation, btw my car is a '07 Civic Si, would I be able to use a decent AUX jack that has a USB plug, I'm having trouble finding one or knowing if it will even work.


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## Yuck. (Dec 28, 2009)

Amazon.com: NEW USB External 3D Sound Adapter Headphone Input: Electronics
Would something like this work?


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## t3sn4f2 (Jan 3, 2007)

Yuck. said:


> wow, pretty amazing if you think about it, is there any amount of data that is lost in the translation so to speak?


What do you mean by translation? 



Yuck. said:


> This presents me with an interesting situation for me because I'm getting my 9987 installed and I was gonna get the kce 422i for $30 or something similar that's compatible, but now I've got to use the stock AUX input...which is disabled with a 'normal' installation, btw my car is a '07 Civic Si, would I be able to use a decent AUX jack that has a USB plug, I'm having trouble finding one or knowing if it will even work.


Not sure exactly what you mean, but the device you posted the link to won't work with an iPod or any head unit for that matter. That is a basic USB soundcard for your computer that runs off windows drivers.

If you want to use the bottom dock connector of your iPod as the way to send audio to the AUX mini jack of a headunit, then you need what is called a "line out dock". It is essentially a male dock connector to mini jack converter that has a few electronic components inside of it to enable the line out on the iPod's or iPhone's dock connector.


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## Yuck. (Dec 28, 2009)

By lost in translation I mean the song data itself, I've been told that, at least with older apple products, the signal suffers from being a 'headphone' connection with limited data transfer, but with HU adjustment and such, it should be reprocessed properly anyway, so I was just confusing myself I guess  And, I beleive that when you put a aftermarket deck in a newer civic, you lose the ability to use the aux Jack, so I'm wondering if there's a USB-to-miniJack cable or a USB-to-aux input solution for me to utilize the USB input in the back of the 9887, and I'll feel real dumb if I go downstairs and look at the 9887 with the faceplate down and see an AUX Jack, we'll see in 30 sec, lol


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## Yuck. (Dec 28, 2009)

Wait, totally stupid actually, no aux jack, and no standard USB input, just that round plus on a cable...just do me a favor and ignore me, lol


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## t3sn4f2 (Jan 3, 2007)

Yuck. said:


> Wait, totally stupid actually, no aux jack, and no standard USB input, just that round plus on a cable...just do me a favor and ignore me, lol


lol. The best option for an 9887 is to use the Fullspeed connection option. It will control a compatible ipod or iphone (chekc to see if yours is) and will use the lineout dock on the buttom instead of the headphone out. you won't have to worry about moving the volume slider on the ipod or anything.


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## Yuck. (Dec 28, 2009)

Yea, I don't think mine is compatable with the fullspeed, thats the kce-422i I reffered to, I'll figure something out, I guess I'll look through the crutchfield forums, they seem to have a lot of people with 9887 ipod/iphone setups, thank you very much tho


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## Yuck. (Dec 28, 2009)

What kind of results would you get throwing in EQ settings from the phone software, less than desirable?


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## jperryss (Mar 15, 2006)

I tossed this out in the other thread that linked to this one, figured it was worth re-asking here...




t3sn4f2 said:


> If you want to use the bottom dock connector of your iPod as the way to send audio to the AUX mini jack of a headunit, then you need what is called a "line out dock". *It is essentially a male dock connector to mini jack converter that has a few electronic components inside of it to enable the line out on the iPod's or iPhone's dock connector*.




There may be more to the BMW LOD you tested with. Do you think those 'components' might have an effect on the measures noise levels, etc? A straight LOD is strictly wires soldered to the pinouts on the dock plug, there's nothing else to it. I think it'd be interesting to test the headphone jack against a decent-quality straight LOD. Really that would be the 'right' way to test.

I don't need to convince myself that the LOD method is better, but I'd be interested in knowing if, and how, the more complex of the two paths yields a cleaner, better signal. Less components should equal less impact on sound.


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## t3sn4f2 (Jan 3, 2007)

jperryss said:


> I tossed this out in the other thread that linked to this one, figured it was worth re-asking here...
> 
> 
> 
> ...


The components used to enable the line out on the dock connector don't go on the signal pins they go on a serial pin and something else. So they would not change the quality. 

The differences in the lod and headphone out result could be due to trivial little things like the extra connectors needed for the lod test rig interface. But don't think you are going to see the noise improve by several dB OVER the headphone out. That would be impossible IMO. I'd saying they are both essentially of same quality and of slightly different output voltages [only because the line out is calibrated (ie cutoff) to a standard AUX out voltage or a lowest possible and inconsequential THD and IMD% #].


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## jperryss (Mar 15, 2006)

t3sn4f2 said:


> The components used to enable the line out on the dock connector don't go on the signal pins they go on a serial pin and something else. So they would not change the quality.
> 
> The differences in the lod and headphone out result could be due to trivial little things like the extra connectors needed for the lod test rig interface. But don't think you are going to see the noise improve by several dB OVER the headphone out. That would be impossible IMO. I'd saying they are both essentially of same quality and of slightly different output voltages [only because the line out is calibrated (ie cutoff) to a standard AUX out voltage or a lowest possible and inconsequential THD and IMD% #].


Interesting. So is it pulling the signal as a digital signal, then converting to analog? I'm a bit puzzled, heh.

I have a cheapo 'normal' LOD that one could typically use for a headphone amp (a bit bulky for that) or to provide a direct signal to a standard aux-in on a car stereo. It just pulls the analog signal off of the pins (bypassing the internal amp) and outputs a straight analog signal. I'd gladly donate it if you were interested in testing it. I'd send my custom-made one but I'd need it back and I think I'd miss it too much.


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## t3sn4f2 (Jan 3, 2007)

jperryss said:


> Interesting. So is it pulling the signal as a digital signal, then converting to analog? I'm a bit puzzled, heh.


No the signal still comes out of the dock connector the same way as it does out of any lineout connection. What the special LOD does for the iPhone is send a special signal (through some resistors connected to special pins) back into the iPhone telling it to turn on the analog lineout. Without that there would be no output.



jperryss said:


> I have a cheapo 'normal' LOD that one could typically use for a headphone amp (a bit bulky for that) or to provide a direct signal to a standard aux-in on a car stereo. It just pulls the analog signal off of the pins (bypassing the internal amp) and outputs a straight analog signal. I'd gladly donate it if you were interested in testing it. I'd send my custom-made one but I'd need it back and I think I'd miss it too much.


Thank but I don't think it would work because of the reasons mentioned above. 

I'll try and find a different connector and test them again this week. Not the lod but the female 3.5mm to rca adapter that it needs to interface with my soundcard.


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## t3sn4f2 (Jan 3, 2007)

While researching the "normalize" option in RMAA I came accross this post by one of the mods on the RMAA forums.

RMAA Pro Wish List - RightMark Forums

"Maxim Liadov:

We all need levels adjustment, but software gain/attenuation is rather useless. It should be provided before ADC and after DAC. *RMAA has auto normalize feature of recording signal in options, but it realy reduces SNR and DR.* We certainly will have made reference hardware with correct adjustable gain/attenuation in future! With one manufacturer or another, but we have to do it. We even did some seriouse steps, but I can't say anymore yet. Please, be patient!"

RMAA needs a specific signal strength in order to give you an all clear for the test run (ie ~-3dB). That number is relative to the input sensitivity of your soundcard. IOW if the soundcard you are using to test with has a max input voltage of .5 volts then all you need to give the input in order to get the all clear from the software is ~.5 volts (the number is the same even though -3db is not full scale since max voltage on a hardware input usually leave some open headroom in the digital domain in order to prevent clipping. If you then have a soundcard with a max input voltage of 4 volt then -3db on RMAA would be that amount.

This is where the normalize feature mentioned above is supposed to come into play. It is supposed to compensate through software for those input voltages that don't max out your inputs. But as you can see it is not perfect and could affect noise performance.

My soundcard, the one I use to test has/needs 2 volts RMS to bring the RMAA level up to -3dB but an iPhone/iPod only has 1 volt and as a result only bring the level up to -8dB. 

RMAA will tell you the level is too low but will still run regardless. I thought it was not an issue and would still give fine accurate results, but I see that is not the case.

So in my the results for the iPhone test, it could actually be even better (SLIGHTLY) then that due to the reasons mentioned above. Using a high quality analog line driver with these under powered devices (underpowered relative to my input needs that is) would yield the more accurate results. 

We aren't going to see a proportional decrease in noise relative to the increase in signal strength though. The 94.5dB S/N ratio plus a 6dB of increased signal strength would put the result past what is possible from the format so don't expect the change to be more then 1 or 2dB. 

I can confirm this since I've compared with headphones the noise level of my iPhone versus the analog outputs of my soundcard and the difference in amplitude when level matched coincides approximately with the RMAA results. IOW, the iPhone is slightly noisier at the same output voltage. 

Adding digital gain on my sound cards 32bit mixer didn't change the RMAA results to any significant amount either.

NOTE: This could also be another reason why the line out dock results are higher in noise compared to the more powerful headphone output.


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## t3sn4f2 (Jan 3, 2007)

t3sn4f2 said:


> Update:
> 
> Don't why I didn't try this earlier but I increased the bit depth of the recording sound card to increase its performance way past what a CD file could perform. Now the results are what the iPhone really is without a limited resolution device measuring it.
> 
> ...


iOS 4 approved.


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## SSSnake (Mar 8, 2007)

I wish I had stumbled across this thread earlier. This is really solid work. THANK YOU!


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## t3sn4f2 (Jan 3, 2007)

SSSnake said:


> I wish I had stumbled across this thread earlier. This is really solid work. THANK YOU!


Anytime. I think I'm gonna run a test with a 32bit/192kHz setting on the recording end to completely eliminate the soundcard from the picture. Should be an nice visual perspective if I can get the different sample rates to come together on one graphical representation. I've never run it like that before so _I'm_ even curious to see the results near the top end of the audible scale.


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## SSSnake (Mar 8, 2007)

Well, if the measurements are even close to correct (which I believe they are) I will never hear that roll off at the top with my 42 year old ears


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## t3sn4f2 (Jan 3, 2007)

SSSnake said:


> Well, if the measurements are even close to correct (which I believe they are) I will never hear that roll off at the top with my 42 year old ears


Yeah it's more of a nit-picking thing. I want to get the FR results as accurate as I can show it.


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## W8 a minute (Aug 16, 2007)

Great thread. I need to search for results of a regular old iPod Classic and compare.


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## TAMUmpower (Jan 29, 2010)

Anyone have results on the headphone jack on the 5th gen iPods? I'm assuming they are probably still pretty good.


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## t3sn4f2 (Jan 3, 2007)

TAMUmpower said:


> Anyone have results on the headphone jack on the 5th gen iPods? I'm assuming they are probably still pretty good.


Which one exactly?

http://support.apple.com/kb/HT1353

Edit: Ah nevermind, the ipod video.

That one is supposed to be the best iPod ever in terms of SQ. In fact it is the only one that Red Wine Audio ever felt was worth modding the analog output of.


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