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

Re: DIY Line Out Cable - Works!

Personally, I think both preout and ampout are used, but I can't prove it. Tracing the circuits on the board is nearly impossible due to it being multilayer. The hint to both being used was when sansafix said the lineout should provide a better SNR. If the lineout is a tap off of the ampout this probably would not be true.
8GB Blue FUZE w/The Original DIY Lineout Cable and AT Button H-Phones Fitted To AT WM5 Headband:All Custom Built
SanDisk Guru
sansafix
Posts: 1,235
Registered: ‎10-24-2007
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Re: DIY Line Out Cable - Works!

Line out is separate from the Headphone output.  It provides an improvement in Audio quality .
SanDisk Fanatic
14124all
Posts: 363
Registered: ‎08-02-2008
0

Re: DIY Line Out Cable - Works!

Thank you sansafix! Well, I thought so! That means the Docks and the modded cable are correct lineout at .7v rms p-p. This is giving us the best available signal the Fuze has.
8GB Blue FUZE w/The Original DIY Lineout Cable and AT Button H-Phones Fitted To AT WM5 Headband:All Custom Built
Newbie
waino
Posts: 4
Registered: ‎12-15-2008
0

Re: DIY Line Out Cable - Works!

I got on this forum looking for line-out cable info and this is my first post. Inspired by 14124all's work (thanks!), I've been performing some experiments on my Fuze, using a voltmeter, power supply, and oscilloscope.  FW version 01.01.11A.

 

First, the Sandisk cable connector: there are two little rectangular holes on the back (non-logo) side, and two hooks

extending into the holes from the front side.  The hooks hold the halves of the shell together.  If you can get pieces of

shim material or similar to fit snugly down into the holes, they should press the hooks out of the way, enabling you to

separate the halves without breaking off the hooks.  The hooks on my connector broke.  The solder on the PCB is RoHS-compliant

and did not stick to my 30-gauge test wires well, so I wicked it out with fine solder braid and applied some good old-

fashioned tin-lead stuff.

 

Now for my electrical measurements.  Pin 7: the line output switches on with 1.82 V and higher on this pin (I tested up to

3.3 V).  The input resistance of pin 7 is 9.1 kohms with Fuze power turned on; higher with power off.  Line out AC

amplitude is not affected by pin 7 voltage, other than being switched on and off.

 

Headphone output: 0 V DC offset.  Output impedance of the headphone amplifier is approximately 20 ohms.  Level into

a high-impedance load, with volume setting on max and "system setting" = High, is the same as that of the line output. 

But of course as others have said, to get this level you must crank up the volume setting, and remember to turn it back

down when you plug your headphones back in.

 

Line out: 1.44 V DC offset.  I saw a maximum AC peak-peak output amplitude of almost 2 V, which

corresponds to 0.7 V rms (by the way, what do you guys mean by rms p-p?  Is this the same as rms AC?).  Output

impedance is very low, on the order of 1 ohm or so (I didn't load it down enough to measure really accurately out of fear

of blowing the amp).  Output level is constant with volume settings above 1/4, and not affected by the "system setting". 

This definitely is not the same amplifier as what drives the headphones, even though the max amplitudes are the same. 


Equalizer: line out is affected by the equalizer.  I found that when using "Custom EQ", if I increased all the frequencies

equally, the amplitude went up but flatness became worse.  With 0 dB settings, flatness was 0.5 dB from 50 Hz to 6 kHz,

and 1.5 dB out to 20 Hz and 16 kHz (the limits of my test tones).  With 12 dB settings, peaks occurred at 400 Hz, 1.25

kHz, and 4 kHz, with 4 dB difference between the peaks and the adjacent valleys.  Even though the 0 dB setting

produces a lower level, the fidelity is better.

 

When I drive my car stereo with the Fuze' line out, the volume is somewhat lower than that of a CD, but not significantly. 

In my application, it is better to change the volume on the stereo than to mess with the equalizer settings.

 

USB 5V: if I plug the USB cord into a PC, both the headphone output and the line out are turned off.  But if 5 V is applied

through the USB cable while the data lines are left unconnected, the Fuze outputs music via either output, while it

consumes 300-350 mA and indicates it is charging.  This means a single car cable can be used to provide line out to a

stereo, and charge the Fuze at the same time.

SanDisk User
axon01
Posts: 49
Registered: ‎12-01-2008
0

Re: DIY Line Out Cable - Works!

Some Very Cool Informantion waino :smileyhappy:

 

 

thanks.......

 

axon

Newbie
ZoNtO
Posts: 9
Registered: ‎12-14-2008
0

Re: DIY Line Out Cable - Works!

So is there anyone here that makes custom LOD for the Fuze to connect to portable headphone amplifiers like the ones people make for iPods over on Head-Fi forums?  Not really sure where to find the dock materials and such, but I'm sure someone has.

 

Any info would be appreciated!  Thanks!

SanDisk User
axon01
Posts: 49
Registered: ‎12-01-2008
0

Re: DIY Line Out Cable - Works!

[ Edited ]

My understanding is that you don't really need a docking cable because Sansafix said the line out is exactly the same as the headphone jack at 100%.

 

This was also verified by waino's post above.

 

axon

Message Edited by axon01 on 12-17-2008 02:39 AM
Newbie
ZoNtO
Posts: 9
Registered: ‎12-14-2008
0

Re: DIY Line Out Cable - Works!

I don't get why Sansafix would say that the lineout was separate from the headphone jack and provided an improvement in audio quality then...  :smileysad:
SanDisk User
calv
Posts: 76
Registered: ‎11-17-2008
0

Re: DIY Line Out Cable - Works!


ZoNtO wrote:
I don't get why Sansafix would say that the lineout was separate from the headphone jack and provided an improvement in audio quality then...  :smileysad:

well, that one is easy: sandisk want's to sell accessories like docking stations. So people at least have to believe that they improve audio quality, because they use line out.

 

Besides that, I also think that line out should not be influenced by eq settings. I don't consider that a bug, but a fauxpas that reveals that line out passes the same signal processing "units" as headphone out does and for that reason can't provide better quality anyway.

 

The non (or barely) existing impedance in line out should be a WARNING for everyone making their own cables to not underestimate the risk of a short circuit, especially when dealing with phone jacks. Please use at least a small resistor.
SanDisk Guru
sansafix
Posts: 1,235
Registered: ‎10-24-2007
0

Re: DIY Line Out Cable - Works!

I said the line out signal level is the same as max headphone out.  However,  the Line out signal path is in fact separate from the heaphone path and has better performance.