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.

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.

@14124all wrote:
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.

LOL, What the big print giveth, the small print taketh away…   check out the 3rd bullet under “Features” .  Griffin is aware of what a line out is, but in the “Features” they refer to it for what it is, is an “audio out”… and printed on the Dock itself are the words “Audio Out,” not line out.  :slight_smile:

Anyway, untold numbers of us have listened to headphones plugged into the Griffin docks with no deleterious effects, and if the “Audio-out” was not supposed to be used by headphones, don’t you think Griffin would mention that?

On to the Clip:  What did you find?  Come on, don’t keep it a secret.  :slight_smile:

axon

PS:  even though we can’t change the volume any more when the Fuze is docked, the equalizer still works. 

HAH! Shoot me right back LOL! I think it is just confusing labeling. The fact is that the dock uses the Fuze lineout signal. I agree that it is not true lineout, but it is at lineout level and it is what the Fuze has available from the SOC IC. You probably won’t find a true lineout in any of the current MP3 players due to the EQ being adjustable. Cowon and maybe older iRiver might have them with fixed flat EQ.

If enough people want the volume control maybe Sansa will reactivate it. I see the main problem as being someone plugging in older large 8 ohm headphones, or a speaker set that is meant to run off of a headphone out signal instead of lineout signal. Either of these could draw too much current and pop the Fuze!

Clip info will be given if I find something worth reporting. Right now it is a couple of board traces that I need to find out where they go.

True lineout or not, by using the lineout signal from the Fuze you are bypassing the internal amp don’t you? That’s the whole purpose of making the cable isn’t it? I would get the Griffin Dock but what’s the point if it has an amp of it’s own?

Hurry up 14124all! You’ll make history! :stuck_out_tongue:

Message Edited by Peyotero on 12-24-2008 11:29 AM

@peyotero wrote:

True lineout or not, by using the lineout signal from the Fuze you are bypassing the internal amp don’t you? That’s the whole purpose of making the cable isn’t it? I would get the Griffin Dock but what’s the point if it has an amp of it’s own?

 

Hurry up 14124all! You’ll make history! :stuck_out_tongue:

 

Message Edited by Peyotero on 12-24-2008 11:29 AM

The Griffin Dock does not have a built in amplifier and if you’ve been following the thread, the line out signal is exactly the same as the headphone jack signal… but don’t worry, it doesn’t matter, the sound quality is fantastic.

axon

“The Griffin Dock does not have a built in amplifier and if you’ve been following the thread, the line out signal is exactly the same as the headphone jack signal… but don’t worry, it doesn’t matter, the sound quality is fantastic.”

You keep repeating that, but the Sansa Rep keeps telling you otherwise - as well as the specs that have been shown for the sound chip.  I guess it’s up to the reader to decide which source is more credible.

Message Edited by PolloLoco on 12-25-2008 11:41 AM

@polloloco wrote:

“The Griffin Dock does not have a built in amplifier and if you’ve been following the thread, the line out signal is exactly the same as the headphone jack signal… but don’t worry, it doesn’t matter, the sound quality is fantastic.”

 

You keep repeating that, but the Sansa Rep keeps telling you otherwise - as well as the specs that have been shown for the sound chip.  I guess it’s up to the reader to decide which source is more credible.

Message Edited by PolloLoco on 12-25-2008 11:41 AM

PL, I believe you are misinformed.

I think all you have to do is plug into the output of the headphone jack at full volume and then the output of the Griffin dock to discover that they are the same volume.

One would assume that if there was amplification in the Griffin dock, the dock would be louder than the headphone out.

What sansafix said was that the line out of the Fuze is the same as 100% volume out of the headphone jack.

What I’m telling you is that the line out of the Griffin dock is the same volume as 100% volume out of the headphone jack.

If you have information to the contrary regarding the Griffin dock, please don’t keep it to youself,  quote it here so that we all might benefit from it.   :)

axon

Well I finished my line out cable -> car stereo project and it works great.  For the cable, I just rewired an existing Sandisk cable.  The cable provides 5 V for charging, and audio on the green and white USB data wires.  On the cable’s circuit board, I cut the traces between the pins and the green and white wires, and re-routed those wires to the audio pins (27 and 28).  Also tied pin 7 to pin 22 to enable the audio.  I run 5 V into the red wire and use the cable shield as its ground return path, while the black wire is the ground reference for the two audio wires.  I found that it is important to keep the audio ground wire separate from the charging ground (although they are tied together in the Fuze), because otherwise a lot of noise shows up in the audio.  This works because my car stereo has + and - inputs both isolated from ground, so the black wire is tied to the - inputs for both channels and the green and white wires go to the separate channels’ + inputs.

The cable of course no longer functions as a computer sync cable.

I built a little circuit board with a 5 V regulator and heat sink, and a USB Type A receptacle, which fits right under the stereo.

I like how the latest FW disables the volume control.  Now there’s no danger of messing up the headphone audio level accidentally.  Sansafix, if you’re listening, I’d like to recommed disabling the equalizer when line out is enabled.  Equalization should be the job of the system you’re driving with the Fuze.  I’d like one equalizer setting to compensate for headphone deficiencies, and a flat output for line out, without having to manually change the settings when switching back and forth between the two.

Waino

Meh,  just set the eq to normal before connecting the cable.

Waino, Nice job on the lineout cable and car specific to boot!!! It’s nice to see that someone else likes to tinker with this stuff!