Showing results for 
Search instead for 
Do you mean 
Reply
SanDisk User
axon01
Posts: 49
Registered: ‎12-01-2008
0

Re: DIY Line Out Cable - Works!

[ Edited ]

sansafix wrote:
Next release of Fuze firmware will output fixed line level when connect to the Dock.

 

Hi sansafix

 

If the firmware is just going to eliminate the ability to control the volume of the dock from the Fuze, my suggestion is to leave it as is.  It's a nice feature to have and since the signal is being controlled digitally, the end result sound quality will remain the same as it is now, whether we can change the volume or not. 

 

If the headphone lead from the DAC chip goes to the headphone jack and the lineout lead from the DAC goes to the docking plug, there is no reason to remove the ability to adjust the volume on the dock.  However, from my experience with the Fuze, I don't believe that is the case.  'To simplify the construction,' and the fact that firmware can alter this feature, leads me to think there is just one lead from the DAC that goes to the volume control and then either to the headphone jack or the docking plug, allowing the Fuze to control the volume of the headphone and the dock. 

 

This is not a bad thing, however, and my advice to SanDisk is to leave it alone.  Firmware is not going to change the source of the sound or the sound quality.  The Dockable Fuze is a winner just the way it is!  There is no reason to remove the volume feature just to make the Fuze have a fixed line level when connected to a dock.   That would be a downgrade rather than an upgrade.

 

axon

Message Edited by axon01 on 12-08-2008 08:53 PM
SanDisk User
axon01
Posts: 49
Registered: ‎12-01-2008
0

Re: DIY Line Out Cable - Works!


neutron_bob wrote:

I like aspects of either configuration, as one could tweak the volume while docked.

 

The advantage of fixed becomes apparent when I use the e200v2 on the dock: the volume setting for the headphone is retained, and restored when I pull the device from the dock.  Quite convenient!

 

Bob  :smileyvery-happy:


 

Hi N_B

 

I don't see the advantage of a fixed lineout.   Right now I can leave my headphone setting right where it is, dock the Fuze and get a line level signal for my office stereo, but I also can lower the line level out to the dock should I want to plug a sensitive headphone into it for listening at home.   And should I need to balance the line out level with my other components (which I don't, it's as loud as my tuner), I have the ability to, as you said above, tweak the volume while docked.

 

axon

SanDisk Fanatic
14124all
Posts: 363
Registered: ‎08-02-2008
0

Re: DIY Line Out Cable - Works!

axon, Now I'm confused! In 2 of your posts you say the headphone out seems cleaner than the dock out and the volume level is near equal. I thought your dock lineout level was low, maybe I misunderstood. So why bother with the dock? Just use a cable on the headphone out since the level is the same and the quality is better or equal and you retain full volume control. The dock also kills FM reception so why bother with it?

8GB Blue FUZE w/The Original DIY Lineout Cable and AT Button H-Phones Fitted To AT WM5 Headband:All Custom Built
SanDisk User
calv
Posts: 76
Registered: ‎11-17-2008
0

Re: DIY Line Out Cable - Works!

The general problem with applying the volume completely digital is the signal to noise ratio of the DAC. For example on a 16 bit DAC with a 16 bit signal the volume setting 25% would require to drop the signals lowest two bits making it in fact a 14 bit signal and so increasing its quantization noise (relative to the full signal).

 

If I read correctly the Fuze's DAC has 18 bit, while all audio played has 16 bit. So if you would like to amplify as much as possible in software (digital) without introducing additional noise, then you would do the lower 25% of the amplification by leaving the digital signal untouched and just amplifying it with an analogue circuit. Beyond this point you can do the amplification in software by multiplying the signal with a factor of up to 4 without overflow and without introducing errors bigger than 0.5 digit.

 

This also relieves the hardware developer mostly of the burden of creating an analogue amplification circuit that is neutral in sound all the way from lowest to highest amplification. You just have to assure that the highest amplification is perfect, then 75% of the volume range is always perfect.

 

So what seems to happen in the current firmware when line out is activated is that the digital amplification is set to max, while analogue amplification still depends on the volume setting as before.

SanDisk Fanatic
14124all
Posts: 363
Registered: ‎08-02-2008
0

Re: DIY Line Out Cable - Works!

calv, Thanks for the excellent explanation! I have only dealt with DAC operation on industrial motor control and was not aware of the audio amp workings. What you have presented explains why the Griffin Dock output will increase from the Fuze volume control to about 25 or 30 percent and then sits at that peak with no more increase all the way up. My lineout cable is probably overdriving the pin7 input and that is why I get a noticeable volume increase over the dock. I'm not hearing audio distortion on a Klipsch Promedia (did hear some clicks at times which may be clipping), but it probably is there and would be heard on axon's DT880s. I'll drop the voltage feed to pin7 with a resistor instead of a straight jumper.
8GB Blue FUZE w/The Original DIY Lineout Cable and AT Button H-Phones Fitted To AT WM5 Headband:All Custom Built
SanDisk User
calv
Posts: 76
Registered: ‎11-17-2008
0

Re: DIY Line Out Cable - Works!


14124all wrote:
calv, Thanks for the excellent explanation! I have only dealt with DAC operation on industrial motor control and was not aware of the audio amp workings.

 

Well, to be honest I have no practical experience with DAC or analogue circuits at all. Its just composed of what I think to have learned at university. Now I'm more of a computer scientist :smileyhappy: so someone who actually knows the matter from real experience might correct me in one or the other thing.

SanDisk Professor
Skinjob
Posts: 682
Registered: ‎04-18-2008
0

Re: DIY Line Out Cable - Works!


14124all wrote:

axon, Now I'm confused! In 2 of your posts you say the headphone out seems cleaner than the dock out and the volume level is near equal. I thought your dock lineout level was low, maybe I misunderstood. So why bother with the dock? Just use a cable on the headphone out since the level is the same and the quality is better or equal and you retain full volume control. The dock also kills FM reception so why bother with it?


 

Yeah, that was my point exactly.  Plus, my main use for a line-out would be in the car, so the dock is less than ideal.

SanDisk Professor
Skinjob
Posts: 682
Registered: ‎04-18-2008
0

Re: DIY Line Out Cable - Works!


14124all wrote:
calv, Thanks for the excellent explanation! I have only dealt with DAC operation on industrial motor control and was not aware of the audio amp workings. What you have presented explains why the Griffin Dock output will increase from the Fuze volume control to about 25 or 30 percent and then sits at that peak with no more increase all the way up. My lineout cable is probably overdriving the pin7 input and that is why I get a noticeable volume increase over the dock. I'm not hearing audio distortion on a Klipsch Promedia (did hear some clicks at times which may be clipping), but it probably is there and would be heard on axon's DT880s. I'll drop the voltage feed to pin7 with a resistor instead of a straight jumper.

 

Interesting.  What is the voltage you're getting on the line-out?  Is it the same as whatever you feed pin-7?

SanDisk Guru
sansafix
Posts: 1,235
Registered: ‎10-24-2007
0

Re: DIY Line Out Cable - Works!

[ Edited ]

Line out is clearly specified as a 700 mv RMS P-P signal.

 

When you connect to the dock,  it should drive this level and you adjust the volume on your stereo.  When you remove the device from the dock,  the headphone setting is restored.

 

This is the way it works with the other Sansa Devices,  and docks,  including View.. 

 

There are two different outputs one for Line out and one for Headphone,  but they share the same DAC.  VOlume adjustment is done in the analog domain,  and digital attenuation at lower levels.

 

So generally speaking,  fixed line out will offer the best SNR signal for your stereo.

 

Using the Sansa Base station,  you can adjust the gain of the preamp using the remote,  but the line level should be unchanged.

 

If you want to use a variable output,  you can connect the headphone output directly to your stereo.

Message Edited by sansafix on 12-09-2008 08:55 AM
SanDisk Professor
bdb
Posts: 434
Registered: ‎04-24-2008
0

Re: DIY Line Out Cable - Works!

So will fixed line-out apply to just the Sansa Base Station, or the Griffin Dock as well?

 

And if someone sells a cable (like the one mentioned in this thread), it might also apply there? (really I wish Sansa would sell that cable; a lot of people want to use these in cars where docking stations are just ridiculous).

 

I'm glad to hear Sandisk is fixing this, and returning the headphone output to its previous level is icing on the cake! Pretty much everything else in the audio world (besides speakers and headphones) use a specific line-level.

 

Its really too bad that people outside this forum aren't all that aware of the features that Sansa has been adding in firmware. I've seen vendors promise this for years, but very few follow through.