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.

Fixed line out will apply to all Docks, including the Griffin.

As for the Cable,  you’ll have to make you own.

sansafix, Thank you very much for the info!

skinjob, The voltage applied to pin7 is DC. It is an enabling input which seems to very the audio output based on it’s level. The lineout level is analog AC, so the voltages are not comparable. The Sansa Dock remote probably varies the DC level on pin7 to control output level. The Griffin Dock applies a fixed DC voltage of approx. 1volt to pin7. My original cable jump puts approx. 3volt DC on pin7. It is clear to me now that it is too much and driving the output too hard. The output is louder, but is most likely distorting or clipping. The ideal signal will be with 1volt DC on pin7. I will determine what resistor value to use as a jumper to get the DC voltage down to 1volt from 3volts. This should produce the same level as the Griffin Dock which should be a true 1v p-p AC (.7v p-p rms AC) on the lineout. Sansafix has said that the firmware will set the lineout level as fixed. This is how most lineout devices apply it. If you need a varied output, the headphone out can be used as it is a very clean signal as is even at 100% volume.

The output signal has nothing to do with the voltage on Pin 7.  That just enables the line out.

Message Edited by sansafix on 12-09-2008 10:44 AM

Wow! Than there is more involved. My straight jumped cable increases the output more than the Griffin Dock output. I’ll have to keep digging!

@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?

Hey 1412 

The dock is only for convenience.  I’m basically using the Fuze as a transportable music player that replaces a CD player in my office system.  All I have to do is plug the Fuze into the dock at my office and I’m good to go.  At the end of the day, I lift the Fuze out of the dock and go home.  The dock is just easier, provides a secure place to hold the Fuze while it’s playing and keeps the screen aimed at an effective angle.

When I want to go portable, I use the Clip.

I ran it the other way before the dock came.  1st I had to plug in the AC power connector, then I had to plug in the headphone jack, then I had to set the volume at 100%, and do the reverse at the end of the day.  Couldn’t see the screen, and I had to make sure it was laying on something that wouldn’t scratch the back or fall off the shelf it was on. 

You don’t really need the dock, but it’s so inexpensive, there was no reason not to get one or two… depending on how you want to use it.  :slight_smile:

axon

@sansafix wrote:

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

Hi sansafix

I don’t understand how the volume is adjusted. 

In my Fuze, at 100%, the volume out of the headphone jack = the volume out of the line out dock.

Where is the analog amplification applied and where is the digital attenuation applied?

axon

Digital attenuation is before the DAC.

Each amplifier,  HP or Line out has adjustable Analog gain.

At full scale,  the HP out will be the same level as line out assuming you use the Volume “High” setting.

@sansafix wrote:

The output signal has nothing to do with the voltage on Pin 7.  That just enables the line out.

@14124all wrote:
Wow! Than there is more involved. My straight jumped cable increases the output more than the Griffin Dock output. I’ll have to keep digging!

So what what the heck is going on then?  I assume this means 14124all’s cable is fine “as is” and doesn’t need a resistor.  But, what’s up with the dock then?  I guess the dock must be doing something to reduce the output level coming from the Fuze?  Weird…

In any case, just to be clear, the jumped cable should be supplying the correct line-out voltage and there shouldn’t be any problem with overdriving, right?

This is great info, and its good to be able to get this much technical information on the inner workings of these devices.  Even better to hear that Sandisk is addressing this further for us.  I do, however, have two simple questions:

  1. Would it be possible to enable line-out without requiring voltage to pin 7?  If so, what are the chances Sansa would allow this with a future FW upgrade, and what (if anything) would be their reasons for not doing so?

  2. Why doesn’t SanDisk want to make a cable?  Seems like it would be a great way to make some extra money, as well as increasing sales to people who buy Ipods instead due to the much greater accessory market.  I can understand that they want to sell their docks for home use, but it would be great for cars, as well as for the portability factor.  Seems like they’d be missing out NOT to make a cable, so what are the reasons against them doing this? 

@skinjob wrote:


@sansafix wrote:

The output signal has nothing to do with the voltage on Pin 7.  That just enables the line out.


 


@14124all wrote:
Wow! Than there is more involved. My straight jumped cable increases the output more than the Griffin Dock output. I’ll have to keep digging!


 

So what what the heck is going on then?  I assume this means 14124all’s cable is fine “as is” and doesn’t need a resistor.  But, what’s up with the dock then?  I guess the dock must be doing something to reduce the output level coming from the Fuze?  Weird…

 

In any case, just to be clear, the jumped cable should be supplying the correct line-out voltage and there shouldn’t be any problem with overdriving, right?

That is strange. 

  • Why do we think the dock reduces the volume? 

  • sansafix said the volumes of the lineout and the headphone jack are the same at 100%.

  • The dock and the headphone jack sound the same to me volume at 100%, therefore one might assume that the dock does not reduce the volume below the level of the headphone jack.

  • Why does 1412’s lineout cable increase the volume above the levels produced by the dock and the headphone jack?  How does it do that?

  • And why does the Fuze need two amplifiers to send the exact same signal to either the lineout or the headphone jack?  Especially if only one output is operational at a time.

I  don’t think I understand what’s going on yet.

axon

None of us has a clear understanding yet. Sansafix has provided some very useful info though. I need to get a complete schematic built of the Griffin Dock, hopefully in the next few days. All must realize that this work is being done blind. No complete Fuze pinout available and no chip pinout engineering data. This is proprietary info and probably will never be found. So tinkering is the way to solve it. Maybe at the price of a player if something goes wrong for me.

axon, I understand your justification for the dock now. Very handy for desk use and charging. This is assuming you get it at the clearance price as you have stated. Buying at full price would be very questionable. I bought one to disect it!

skinjob, My current cable jump I would call marginally useable. It seems that it is overdriving the output. People can try it and see if they run into distortion on their hookups. I’ll dig out my old Hameg o-scope and see what the actual levels I’m dealing with are.

Since pin7 is a binary on/off enable input the voltage level means nothing, 1-3 volts is going to be the same.

I want to get the cable connected output level the same as the Dock output, as it is probably the cleanest signal available. It will also be proper if the peak to peak value is correct as “true” lineout. My next guess without tinkering is that there may be a pin or pins that get grounded when docked. The cable mod does work on enableing the lineout, but I feel it can be improved.

sansafix, the 3 volts on pin 22, can they be used to power other devices? If yes, how many mA can safely be used?

@cruiserdude wrote:

This is great info, and its good to be able to get this much technical information on the inner workings of these devices.  Even better to hear that Sandisk is addressing this further for us.  I do, however, have two simple questions:

 

  1. Would it be possible to enable line-out without requiring voltage to pin 7?  If so, what are the chances Sansa would allow this with a future FW upgrade, and what (if anything) would be their reasons for not doing so?

 

  1. Why doesn’t SanDisk want to make a cable?  Seems like it would be a great way to make some extra money, as well as increasing sales to people who buy Ipods instead due to the much greater accessory market.  I can understand that they want to sell their docks for home use, but it would be great for cars, as well as for the portability factor.  Seems like they’d be missing out NOT to make a cable, so what are the reasons against them doing this? 
  1. Sansafix has indicated it is possible via FW, but they have decided not to do it.  You would need a setting to enable either the phones or the line-out.  Since you can’t have both at the same time, I guess they were afraid users would set it to line and not be able to figure out why their headphones don’t work.  Seems to me this could be handled easilly in the UI with some kind of status icon (for example, in the same way you know if shuffle is on or not).

  2. I have no idea.  It makes no sense.  Especially since the official Sansa dock is so expensive.  I doubt that many people are willing to spend $50-60 on a dock, but I would think many would buy a $10-15 cable.  And as you said, a dock is not really useful for car and other portable applications.  And if they implemented an output switch in FW, you could use the existing View A/V cable.  They wouldn’t need to make a special Fuze cable.

Dont try powering other devices from the Fuze,  its not supported.

@14124all wrote:

None of us has a clear understanding yet. Sansafix has provided some very useful info though. I need to get a complete schematic built of the Griffin Dock, hopefully in the next few days. All must realize that this work is being done blind. No complete Fuze pinout available and no chip pinout engineering data. This is proprietary info and probably will never be found. So tinkering is the way to solve it. Maybe at the price of a player if something goes wrong for me.

axon, I understand your justification for the dock now. Very handy for desk use and charging. This is assuming you get it at the clearance price as you have stated. Buying at full price would be very questionable. I bought one to disect it!

skinjob, My current cable jump I would call marginally useable. It seems that it is overdriving the output. People can try it and see if they run into distortion on their hookups. I’ll dig out my old Hameg o-scope and see what the actual levels I’m dealing with are.

Since pin7 is a binary on/off enable input the voltage level means nothing, 1-3 volts is going to be the same.

I want to get the cable connected output level the same as the Dock output, as it is probably the cleanest signal available. It will also be proper if the peak to peak value is correct as “true” lineout. My next guess without tinkering is that there may be a pin or pins that get grounded when docked. The cable mod does work on enableing the lineout, but I feel it can be improved.

Hi 1412

What I don’t understand is this: 

  • If the lineout and the headphone jack (at 100%) are the same, how is it possible that your cable can output more than there is?

  • And if the lineout and the headphone jack produce the same signal, they should be able to be used interchangably.

  • And if they are interchangable, a true line level output can be obtained from the headphone jack at 100% while preserving the FM function.  [Regarding the FM function, while I was not able to get satisfactory reception with a .5M Zu Pivot, a plain, el cheapo, unshielded, Radio Shack 1M mini to RCA did the trick.]

axon

@skinjob wrote:


@cruiserdude wrote:

This is great info, and its good to be able to get this much technical information on the inner workings of these devices.  Even better to hear that Sandisk is addressing this further for us.  I do, however, have two simple questions:

 

  1. Would it be possible to enable line-out without requiring voltage to pin 7?  If so, what are the chances Sansa would allow this with a future FW upgrade, and what (if anything) would be their reasons for not doing so?

 

  1. Why doesn’t SanDisk want to make a cable?  Seems like it would be a great way to make some extra money, as well as increasing sales to people who buy Ipods instead due to the much greater accessory market.  I can understand that they want to sell their docks for home use, but it would be great for cars, as well as for the portability factor.  Seems like they’d be missing out NOT to make a cable, so what are the reasons against them doing this? 

 

  1. Sansafix has indicated it is possible via FW, but they have decided not to do it.  You would need a setting to enable either the phones or the line-out.  Since you can’t have both at the same time, I guess they were afraid users would set it to line and not be able to figure out why their headphones don’t work.  Seems to me this could be handled easilly in the UI with some kind of status icon (for example, in the same way you know if shuffle is on or not).

 

  1. I have no idea.  It makes no sense.  Especially since the official Sansa dock is so expensive.  I doubt that many people are willing to spend $50-60 on a dock, but I would think many would buy a $10-15 cable.  And as you said, a dock is not really useful for car and other portable applications.  And if they implemented an output switch in FW, you could use the existing View A/V cable.  They wouldn’t need to make a special Fuze cable.

Hmm, yeah, its wierd that they seem to be keeping quiet on their reasoning behind either of those questions.  I’m not calling them out by any means, and I certainly understand that sansafix can’t tell us something if SanDisk doesn’t want him to, but it still bugs me as to why they don’t seem to want to give us a reason.

 Don’t get me wrong, I’m very grateful that they’re so involved here, and actually listen to our questions, problems, and requests, great customer feedback!  I just get very curious when I feel that the reasoning behind something is being hidden.

 At this point, all I can think of is that they are afraid of competition with the View, though this would be rather illogical.  The hardware on the Fuze does not enable a video-out, and due to the lower SQ, I doubt anyone will buy a View strictly for audio line-out purposes, so its not like they’d be robbing people away from the View.  (I hate to say it, but with the lower SQ, larger size, and higher price, the View isn’t nearly as attractive a purchase, anyway, just my honest opinion.)  Regardless, I can understand certain reasons why they may not want to enable this in FW, though I still think it could at least be a rather hidden-away option for us more advanced users to enable.  Like, bury something in the system settings about enabling line-out, and if its “switchable”, rather than “off”, we’d have an extra icon on the home screen, or you could just hold the center button from the home screen, to switch between line-out and headphones.  That way we could take advantage of it, but the users who would get confused would never enable this option, anyway.  Then y’all could sell us an audio output cable and make some extra cash!

axon, These are only assumptions.

I don’t think the lineout and headphone jack are the same signal. Going by the block diagram of the AMS chip, the headphone amp circuit is built into the chip (it does not seem to be an outboard IC with a preamp feed). The lineout (preamp) signal and headphone amp signal come out of the chip independantly. The lineout will be of high impedance (probably 10-20k ohm) to drive high impedance inputs. The amp out will be of low impedance (probably around 32 ohm) to drive low impedance headphones. Sansafix has stated that the lineout should produce the better signal to noise ratio, which is to be expected from a high impedance signal that does not go through another amp gain stage.

Why is my cable getting a stronger signal - good question. Wish I knew! Note that when you connect to the dock, the volume is adjustable to about 25% and then it does not increase. There is probably more there as calv has explained with his DAC explanation, but it is being limited to avoid signal degradation. Sansafix has also stated that it is at .7v rms p-p line level. The cable is no doubt higher than that. When connected to my Klipsch Promedia with the the Klipsch volume all the way down, I still get some  sound output. The input is being overdriven. Why? A big guess here! The AMS chip may have an adjustable preamp for the lineout, instead of being fixed. If it is uses op-amp circuitry and there is an open (floating) input, it may produce a higher gain on the op-amp output. So, if there is a connection in the Griffin dock that grounds an input, and my cable does not have it, it may produce more gain and a louder signal. Could also be that there is more to it than just enabling pin7. I hope to find out more when I get a full drawing together of the Griffin Dock circuit.

Are they interchangeable? Hard to say! If you can’t hear much difference between amp out and dock out with your M3 and beyer DT880s, than a mini-RCA or mini-mini is probably fine in the headphone jack. I think what is killing us here is that the headphone out signal in the Fuze is overly good. It is very clean all the way up to full volume.

Just want to remind you, that everything that uses phone jacks is prone to short circuits while inserting the plug. Adding resistors is the easiest way to prevent the current from going to “infinity” (which would fry ICs), but on the other hand it decreases the signal level. The size of the resistor that is needed to limit the current with a given max voltage can easily be calculated with ohm’s law.

@14124all wrote:

Sansafix has also stated that it is at .7v rms p-p line level. The cable is no doubt higher than that. When connected to my Klipsch Promedia with the the Klipsch volume all the way down, I still get some  sound output. The input is being overdriven.

 Maybe the change to a fixed line out in the upcoming FW that sansafix mentioined will improve this situation?

@14124all wrote:

Are they interchangeable? Hard to say! If you can’t hear much difference between amp out and dock out with your M3 and beyer DT880s, than a mini-RCA or mini-mini is probably fine in the headphone jack. I think what is killing us here is that the headphone out signal in the Fuze is overly good. It is very clean all the way up to full volume.

The heaphone out is definitely clean, the issue is really just the lower level.  I use it to connect to my car’s head unit and it sounds pretty good.  However, to get a decent level, I have to MP3Gain to 92dB, boost the Fuze’s EQ about halfway up across all freqencies and set the gain on the head unit’s line-in to max.  With all that, I get a level appoximately the same as playing a CD in the head unit.  Despite all the boosting, it still sounds suprisingly good.  But surely a true line source with no EQ on the Fuze and no/moderate gain on the head unit’s input would be a lot better.