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Will a portable amp work in this case?

post #1 of 12
Thread Starter 

Not sure if this is the right forum to post this but I thought this might be relevant.

 

So basically, I have a new Galaxy S4, but it seems to have problems driving my Logitech UE600 earphones. Basically, when I set the volume above 50% to 75%, there is a noticeable 'crackling' sound in my audio, apparent mostly within the bass range. At first I was puzzled... but after reading this forum maybe I know why.

 

Based on the impedance graph I found here: http://www.innerfidelity.com/images/UltimateEarsUE600.pdf, it seems that my IEM's impedance goes below 10ohms until 1kHz where it increases. I suspect the S4 may be inadequate in supplying enough current at the bass range, causing noticeable crackling noises.

 

The S4 has no noticeable distortion when driving my ATH-M50 nor using its stock earphones.

 

So, do you think my hypothesis that the S4 is supplying insufficient current to my UE600 correct? Given the S3/Note 2 has an impedance of about 3ohms, perhaps the S4 has a similar high impedance rating.

 

In that case, would getting a portable amp theoretically solve the problem, if I connect it through the 3.5mm headphone jack? Or will there also be distortion on my portable amp, since the FiiO E7, for example, has an impedance rating of ~0.5ohms. In essence, would an amp amping an in-built amp solve the issue I am experiencing?

 

Many thanks!

post #2 of 12

If the amp you are using will in fact drive your headphones well, then it could indeed solve your problem.  Amplifier output impedance is not the whole story, though perhaps one of the more important aspects.  Output impedance along does not always indicate the ability of an amplifier to drive a load.  Just make sure whatever amp you get can be returned or exchanged if it doesn't work for you.

post #3 of 12
Thread Starter 

I am just using an IEM, so it should be relatively easy to drive. How will an amp overcome the lack of power and reduce crackling/distortion on the original source though? Given the phone has an integrated amplifier and I am actually connecting an amplifier to the integrated amplifier... This is the part I don't really get!

post #4 of 12

If the phone is capable of delivering an undistorted signal into a light load (higher impedance), then what the amp does is act like a buffer and present a very light load to the phone while providing higher output capability to the headphones.  It's role is that of a "power amplifier".

post #5 of 12
Thread Starter 

So in essence an amplifier actually has rather high impedance on its input but outputs a low impedance signal?

 

Also, is the audio 'crackling' issue otherwise known as audio clipping?

 

https://www.dropbox.com/s/hpj205cxbsn9umo/Memo%281%29.m4a

 

I recorded a 150Hz test tone with the output from my UE600. When I crank up the volume up to 100% I get this weird noise, when I turn it down it plays the 150Hz test tone as per normal. Is this audio clipping in action?

post #6 of 12
Quote:
Originally Posted by trenzterra View Post

So in essence an amplifier actually has rather high impedance on its input but outputs a low impedance signal?

Yes, in the case of a headphone amp, the amp has a very high input impedance, on the order of many thousands of ohms, but the output typically has a very low output impedance, and hopefully the ability to provide at least some power into a low impedance load.

 

Quote:

Originally Posted by trenzterra View Post

Also, is the audio 'crackling' issue otherwise known as audio clipping?

 

https://www.dropbox.com/s/hpj205cxbsn9umo/Memo%281%29.m4a

 

I recorded a 150Hz test tone with the output from my UE600. When I crank up the volume up to 100% I get this weird noise, when I turn it down it plays the 150Hz test tone as per normal. Is this audio clipping in action?

I would have guessed that you were hearing clipping, but I don't know how you recorded that file, and the signal in it isn't typical of clipping.  How did you make that recording?  

post #7 of 12
Thread Starter 

I used my old iPhone's voice memo feature to record the sound from my IEM.

 

Here's one of a normal song: https://www.dropbox.com/s/q7r6rlfkbqnjtzw/Memo%282%29.m4a

 

The static you hear in the middle of the song is what I'm hearing from the IEM... Is this audio clipping? On certain test units at Samsung stores, this 'static' is so bad that you can't even hear the song.

post #8 of 12

Wow, that's' really nasty.  But recording it this way does make it a bit hard to analyze.  I'd like to assume it's some sort of clipping, though.  You should try an amp and see if you can work around it that way.  

post #9 of 12
Thread Starter 

Yep, will go and try one when I have the time!

 

By the way, do you think such an issue could ever be resolved in firmware? Or it's squarely a hardware issue?

 

If I use a impedance adapter, will it help? Or it would be equivalent to running the thing at a lower volume (which would then be pointless)?

post #10 of 12
Quote:
Originally Posted by trenzterra View Post
By the way, do you think such an issue could ever be resolved in firmware?

Probably not.

Quote:

Originally Posted by trenzterra View Post
 Or it's squarely a hardware issue?

Probably.

Quote:

Originally Posted by trenzterra View Post

If I use a impedance adapter, will it help? Or it would be equivalent to running the thing at a lower volume (which would then be pointless)?

An amplifier is, among other things, an "impedance adapter".  So is a transformer, but I'm not aware of such a device specifically made for this situation, though it would be possible, and may help.

post #11 of 12
Thread Starter 

Thank you for your help!

 

By the way, it appears someone seems to have the issue with the Beyerdynamic DT-250 (250ohms impedance version), with volume even at 20% (over here: http://forum.xda-developers.com/showpost.php?p=41058621&postcount=24). In this case, does this mean there could be some other issue involved since impedance is rather high in this case? I've no idea how to isolate the cause of this problem...

post #12 of 12

If the S4 is anything like the S3 then it will absolutely suck with IEMs and suck slightly less with fullsize headphones. HTC phones have better audio in that respect.

 

There are solutions out there, like V-Moda's clip on DAC/amp thing and the like, but they are pricey.

 

This is why I still carry around a Sandisk Clip along with my S3.

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