DIY Line Out Cable - Works!

Line out is separate from the Headphone output.  It provides an improvement in Audio quality .

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.

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.

Some Very Cool Informantion waino :slight_smile:

thanks…

axon

@waino wrote:

by the way, what do you guys mean by rms p-p?

I believe “p-p” = “peak to peak”

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!

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

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…  :cry:

@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…  :cry:

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.

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.

Hey 1412

I have a thought for you…  do you think it’s possible to make a Fuze to ipod adapter? 

Just enough rewiring to be able to use some of the ipod docks and peripherals that are on the market.

axon

That would be glorious.  I mean if we have this site here then wouldn’t it be possible to take the information that’s been posted about the pins and make something similar to the Ipod LODs that are so prevalent over on head-fi?  There should just be a R, L, and ground and then that internal connection right?

I should point out that Line Out’s very low impedance was determined by driving a resistive load tied to a 1.44 V DC power supply, so as not to introduce any DC currents.  The smallest resistor I tested with was 33 ohms.

I have no idea what would happen if you shorted the output to ground or even tried to drive 33 ohms to ground.  You might well blow something up all right!

Preamp output impedance of 0 ohms is ideal, but impossible. It is quite common for preout impedance to be very low, many of the opamp preouts go less than 1 ohm with .3 ohm being quite common (and nearly ideal). Looks to me that is what the AMS chip utilizes. That’s probably why the preout (lineout) drives ear buds quite well. I would not use much less than 32 ohm load though (due to current draw), and nothing with large voice coils.

Mini jack shorting spikes due to dv/dt? Doesn’t seem to be a problem with my jumped cable connected hot multiple times with no resistors added.

Fuze to iPod adapter? Probably quite easy if the dock only needs a lineout signal and device detect. Volume control may get involved depending on how/if  it is done. A cable is possible, but the player would not sit in a dock. It would be better to modify the dock internally so the player could sit in it.

Griffin volume control back? Reload firmware 11 or 15 or modify dock by adding a dual attenuator pot.

@14124all wrote:

Preamp output impedance of 0 ohms is ideal, but impossible. It is quite common for preout impedance to be very low, many of the opamp preouts go less than 1 ohm with .3 ohm being quite common (and nearly ideal). Looks to me that is what the AMS chip utilizes. That’s probably why the preout (lineout) drives ear buds quite well. I would not use much less than 32 ohm load though (due to current draw), and nothing with large voice coils.

Mini jack shorting spikes due to dv/dt? Doesn’t seem to be a problem with my jumped cable connected hot multiple times with no resistors added.

Fuze to iPod adapter? Probably quite easy if the dock only needs a lineout signal and device detect. Volume control may get involved depending on how/if  it is done. A cable is possible, but the player would not sit in a dock. It would be better to modify the dock internally so the player could sit in it.

Griffin volume control back? Reload firmware 11 or 15 or modify dock by adding a dual attenuator pot.

Why not just turn it back on?  It wasn’t bothering anybody, and besides, I think it’ll have to be turned on again for the “Sansa Dock’s” remote volume control to work.

axon

Don’t count on it being turned on. With it fixed it is pegged at the best possible signal the Fuze can produce. Also, this will discourage people from connecting low impedance loads to the lineout jacks which if too low may cook something in the player. Remember, electronic components work fine as long as you keep the smoke inside them. If you let the smoke out, they are dead!

I may be wrong, but I think the Sansa Dock has it’s own amp. So the remote probably runs the internal amp and the lineout level can be fixed without causing functional problems.

@Allah wrote:

Don’t count on it being turned on. With it fixed it is pegged at the best possible signal the Fuzz can produce. Also, this will discourage people from connecting low impedance loads to the lineout jacks which if too low may cook something in the player. Remember, electronic components work fine as long as you keep the smoke inside them. If you let the smoke out, they are dead!

I may be wrong, but I think the Sansa Dock has it’s own amp. So the remote probably runs the internal amp and the lineout level can be fixed without causing functional problems.

I’m not sure I follow you 1412.  What kind of low impedance load might be plugged into the dock?  I just want to be able to use the sleep function on the Fuze and a headphone from the dock, without having to fire up an external amp or connect it to a stereo and then leave them on all night after the Fuze shuts itself off.

axon

Edit:  just to say that if the Sansa Dock has a built in amplifier, it better be a really good one or there goes the sound quality…  and I believe I read that the Sansa Dock controls the volume from the e200.  Besides, the whole dock, with a remote, only costs $50.  So how good could the amp part be?  The last thing I would want to do is run my Fuze through a cheap amp and then into one of my headphone amps or a stereo system.

Message Edited by axon01 on 12-21-2008 04:17 AM

Low impedance loads are headphones,ear buds and speakers that do not have linein. Lineout connections are not made to drive them. You don’t connect your headphones to the lineout on a home cd player. You don’t hookup speakers to the lineout on a car stereo or home receiver. Lineout specs are generally into a 10k ohm load on the linein, which draws very little current as to not load down the signal. Lineout connections are made for linein connections. If the Griffin Dock was made to drive headphones, it would have a headphone jack supplied from an amplifier stage. It simply does not have this.

@14124all wrote:
Low impedance loads are headphones,ear buds and speakers that do not have linein. Lineout connections are not made to drive them. You don’t connect your headphones to the lineout on a home cd player. You don’t hookup speakers to the lineout on a car stereo or home receiver. Lineout specs are generally into a 10k ohm load on the linein, which draws very little current as to not load down the signal. Lineout connections are made for linein connections. If the Griffin Dock was made to drive headphones, it would have a headphone jack supplied from an amplifier stage. It simply does not have this.

I understand what you’re saying about a line out, but I don’t think the fuze has a true line out and the Griffin dock definitely does not have a “line out”.  It has an “audio out port” on the back.  In the instructions that come with the dock, Griffin tells you that it has an audio out port that can be used with a standard 3.5mm audio connector cable.  It goes on to say that an external power supply is recommended to conserve battery life when the audio out function is selected.  If there was a problem connecting ear buds or headphones, which have this same 3.5mm  connector, Griffin would, at least, mention it, or label the jack, “line out”, not “audio out”.   No??

Further proof is that when connected to a revealing headphone amp, the “headphone out” sounds cleaner than the Griffin “audio out port” although they are both the same volume…  

axon

Griffin Dock does not have a lineout? http://www.griffintechnology.com/products/docksansa What does it say in the upper left corner below the pictures? This has become an endless circle - enough said. Need to move on to Fuze cable improvements and a possible interesting find inside the Clip.