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The point of using LOD because of bit depth?

post #1 of 19
6/25/11 at 8:43am
Thread Starter 

Are all DAPs software volume control?   If so, at lower volume, there will be loss of bit depth and lose dynamic range.  Is that the reason for using the LOD?  So, therefore, using an amp out of headphone out is pointless unless you just need some more juice to drive low efficiency headphones, but the dynamic range will still be less and there will not be as much sound resolution.


Edited by user02 - 6/25/11 at 8:49am
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post #2 of 19
6/25/11 at 11:31pm
Thread Starter 

no one?

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post #3 of 19
6/25/11 at 11:42pm

As far as I know is the main reason of using a LOD to bypass the headphones amplification circuit of the DAP. Further the Line Out has a fixed voltage of normally 0.775V and a high output resistance in contrary to the low output resistance of your headphone output but the signal isnt altered by the internal amplification circuit.

 

Because of the high output resistance you will need an amp when using the Line Out..

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post #4 of 19
6/26/11 at 7:40am
Thread Starter 

I think what you have stated is true for imod or diymod, but not for a typical ipod line out.  I think what it does is it bypasses the attenuation stage or volume control.  The volume control is software?  Not sure.  Line out is the maximum signal, so I would think it is the unattenuated signal. I know diymod ouputs directly from the DAC, but I don't think ipod LO is.  Maybe the only difference between LO and diymod LO is bypassing of the caps, and the wolfson DAC?
 

Quote:
Originally Posted by monoethylene View Post

As far as I know is the main reason of using a LOD to bypass the headphones amplification circuit of the DAP. Further the Line Out has a fixed voltage of normally 0.775V and a high output resistance in contrary to the low output resistance of your headphone output but the signal isnt altered by the internal amplification circuit.

 

Because of the high output resistance you will need an amp when using the Line Out..



 


Edited by user02 - 6/26/11 at 7:56am
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post #5 of 19
6/26/11 at 7:53am
Quote:
Originally Posted by user02 View Post

I think what you have stated is true for imod or diymod, but not for a typical ipod line out.  I think what it does is it bypasses the attenuation stage or volume control.  The volume control is software?  Not sure.  Line out is the maximum signal, so I would think it is the unattenuated volume.  I know diymod ouputs directly from the DAC, but I don't think ipod LO is.  Maybe the only difference between LO and diymod LO is bypassing of the caps, and the wolfson DAC?
 



 

 

You are right maybe. At least I remember that there was a thread which deals with the Line out of the ipod but dont ask where..

 

Sorry!!

 

Hm..maybe the member ClieOS or nikongod :) may help..

 

 


Edited by monoethylene - 6/26/11 at 8:45am
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post #6 of 19
6/26/11 at 8:00am
Thread Starter 

By attenuation I mean the reduction of signal outputted from DAC because of the software converting bits to analog at a certain level opposed to maximum level(for maximum loudness) for a specific loudness level.  It is not the kind of attenuation that a resistive circuit does taken from maxium bit level converted to analog.  Therefore, dynamic range information is lost if attenuation is done through software.  There is resolution loss.

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post #7 of 19
6/26/11 at 8:09am

Yeahhh, I know what you mean right now..Nevertheless I wasnt going deeper in that stuff concerning LODs from DAPs because I am happy with my Clippi :)

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post #8 of 19
6/26/11 at 8:18am

The point of the line-out on the Ipod is that it skips the junky headphone output stage entirely and replace it with a dedicated unit. 

 

 

Volume control in portable players is almost always done in software. It takes an extra chip to have an analog volume control: that sucks up PCB real-estate & battery life. Many newer DAC chips have a volume control built in, and its not hard to process externally if not. 

 

Stock Ipod line out comes straight off the DAC through some caps to the outputs. 

Imod bypasses the caps in the ipod and replaces them with external caps which allows more room for "bigger and better" caps like film types.

 

When used "tastefully" (between max level and 20db of attenuation) digital controls actually work quite nicely. The problem is that pretty much nobody on head-fi, or in most of audio-philia for that matter, has gain structure that allows only 20db of attenuation so digital controls get an undue bad rap. Even resistive analog volume controls work better at lower attenuation (max volume), but they are not quite as offensive as digital controls at -50db.

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post #9 of 19
6/26/11 at 8:21am
Thread Starter 

The reason why people do not like headphone out to LO is because the belief that there is components in between from headphone out that cause the signal to be impure.  I don't know how much of this is true as long as you turn the volume all the way up if the software or the DAC is controlling the volume.  So therefore, max volume of headphone out and LO are equal if that is the case.  Clip at max volume is like LO if the software is controlling the volume levels.  I have a LOD for fuze, and it bypasses the caps, so it's a different case.  The ipod LO does not because you do not need capped LOD for it.  I will have to conclude LO and headphone out at max volume is equal ipod. If that is true, so many people has been wasted efforts on LOD cables ipods.  Also, the only difference between diymod or imod and LO is the bypassing of the internal caps and specific model of the ipod which carry wolfson DACs. Therefore, if you do not want to bypass the internal capps, get the 4th and 5th gen ipods and will be satisfied with it being a imod or diymod without the cap modification in the signal path.
 

Quote:
Originally Posted by monoethylene View Post

Yeahhh, I know what you mean right now..Nevertheless I wasnt going deeper in that stuff concerning LODs from DAPs because I am happy with my Clippi :)



 


Edited by user02 - 6/26/11 at 8:33am
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post #10 of 19
6/26/11 at 8:31am
Thread Starter 

Someone brave enough to open their ipod, please open up a imod, I really want to know if it indeed the same a diymod.

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post #11 of 19
6/26/11 at 8:36am

So, all in all we are not talking about a real LO??


Edited by monoethylene - 6/26/11 at 8:46am
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post #12 of 19
6/26/11 at 8:39am
Thread Starter 

So the ipod has analog volume control built in opposed to controlling volume from the DAC?  Wouldn't that output better bit-depth?  I'm curious how the chip handles the analog volume control, any link to the datasheet?  I want to know how it compares to a portable amp's volume control.
 

Quote:
Originally Posted by nikongod View Post
Volume control in portable players is almost always done in software. It takes an extra chip to have an analog volume control: that sucks up PCB real-estate & battery life. Many newer DAC chips have a volume control built in, and its not hard to process externally if not. 

 

 



 


Edited by user02 - 6/26/11 at 8:41am
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post #13 of 19
6/26/11 at 8:46am
Thread Starter 

I wish somebody would do a imod, ipod without mod LO, and headphone out signal analysis.  I don't have the equipment to do it, or too lazy to figure out RMAA.

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post #14 of 19
6/26/11 at 8:53am
Quote:
Originally Posted by user02 View Post

So the ipod has analog volume control built in opposed to controlling volume from the DAC?  Wouldn't that output better bit-depth?  I'm curious how the chip handles the analog volume control, any link to the datasheet?  I want to know how it compares to a portable amp's volume control.
 

 

Im pretty sure the ipod controls volume in software. 


A device like the PGA2320 is what I was thinking about, although theres probably loads more.

Its basically a complicated analog stepped attenuator with input and output buffers/opamps on 1 chip. 0.5db steps are really nice though.

 

Digital attenuation just throws away bits. 

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post #15 of 19
6/26/11 at 8:56am
Thread Starter 

Well, I'm relieved to hear that(quality of the attenuator is of another matter), but is there any DAPs anybody know of that throw away bits for lowering volume?

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