DIY Line Out Cable - Works!

@14124all wrote:

Finally dived into the line out cable project. Already had a Fuze internally jumped for line out, did up a cable this time. Attached a 1/8" stereo mini plug to a Sandisk original 30 pin cable.

NOTE: This DIY mod is for those who have good soldering skills. I will not cover the basic mechanics of taking the 30 pin cable connector apart and reassembling. Here are the connections:

  1. jumper pin 7 to pin 22 (this provides the needed 3volt for enabling the line out pins)
  1. stereo cable right channel to pin 27 (usually red wire)
  1. stereo cable left channel to pin 28 (usually white wire)
  1. stereo cable shield to connector housing shield solder point

Operation will be the same as with the Griffin Dock. Charging still works the same, as the original circuit is not altered.

NOTE: There has been much discussion about this not being a true line out signal, which is probably true. A true line out would be unaffected by volume or tone with constant output. It seems to be all we have to work with in the Fuze though. The volume needs to be at about 50% or greater (doesn’t really increase much from that point on, like the griffin dock). The signal is noticeably stronger than using the headphone out and is still distortion free. It drives my Klipsch Promedia 2.1 very well and my Kenwood car stereo equally well.

The advantage of the cable over the dock is that external power is not needed. You can run off of the battery or connect to a USB power source, your choice.

With the cable connected the headphone out is inactive, same as the Griffin Dock. You could run wires out from the pin 7 to pin 22 jumper to a small switch if you want to shut off the line out and restore headphone out.

Hope this clears up some of the conFuzion!!!

 Hi 14124all

Nice work on the line out cable.  :slight_smile:

I’m curious about what you said about the line out. I’m new here and haven’t found much information about the nature of the line out on the Fuze.  For instance, why does the line out need 3 volts?  What else might you be able to say about how the line out works?

  • My experience with the Griffin dock is that the volume remains constant until the last 25%…  do you think this decrease in volume is attenuation of the line out signal? 

  • I also found that anywhere from about 25% to full volume out of the dock was the same as full volume from the Fuze’s headphone jack, when connected to my M^3 amp and DT880 headphones. 

  • I found both signals to be distortion free but  did not find the dock to be  stronger nor better than the headphone out of the Fuze. 

  • I thought the cleaner signal came out of the headphone jack on the Fuze , which makes sense considering the cheap electronics in the dock and the additional signal path. 

  • It should be noted that the difference in sound quality  between the dock and the headphone jack on the Fuze were quite small and without a very resolving system, would not be heard easily.

Regards

axon

Now the disclaimer:  I did the comparisons quickly and I’m aware that YMMV.  :wink:

axon01 wrote: 

  • I thought the cleaner signal came out of the headphone jack on the Fuze , which makes sense considering the cheap electronics in the dock and the additional signal path.

The cleanest signal in any system should be the line out as, properly implemented, it is the ‘earliest’ analogue signal in the chain and thus not impacted by any additional signal path such as the Fuze’s headphone amplifier stage. In the Fuze, it should be the signal which feeds the input of the headphone amp stage. The cheap electronics in the dock are irrelevant as they come after the line out stage and it’s up to you what standard of electronics you feed it into.

axon01 wrote: 

I’m curious about what you said about the line out. I’m new here and haven’t found much information about the nature of the line out on the Fuze.  For instance, why does the line out need 3 volts?

The 3 volts is not on the line out itself, but is necessary to enable the line out.  Ordinarilly, the dock would supply the 3 volts on a certain pin.  This tells the Fuze it’s connected to a dock and should enable it’s line-out and disable it’s headphone out.

As to the other comments about SQ through the dock, it will be interesting to see how much difference there is between a simple cable with no extra electronics versus the dock where the signal passes through another circuit board.

@axon01 wrote:


@14124all wrote:

NOTE: There has been much discussion about this not being a true line out signal, which is probably true. A true line out would be unaffected by volume or tone with constant output. It seems to be all we have to work with in the Fuze though. The volume needs to be at about 50% or greater (doesn’t really increase much from that point on, like the griffin dock). The signal is noticeably stronger than using the headphone out and is still distortion free.


My understanding is that it’s a true line-out.  The volume adjustment is applied digitally in the DSP before the analog output stage and the analog signal is not altered in any way.  The voltage on the line-out should be constant.

This is quite different from many (all?) ipods where the volume adjustment is applied to the analog signal, causing a variable output and poor sound quality.

Exactly.  The Sansa is doing the modifications in the digital domain, so it’s not an old school issue of “more things in the signal path”.  The gain of the output is variable, but it’s the same device, not an added gain stage or rheostat.

Bob  :wink:

@fifer wrote:


axon01 wrote: 

  • I thought the cleaner signal came out of the headphone jack on the Fuze , which makes sense considering the cheap electronics in the dock and the additional signal path.

The cleanest signal in any system should be the line out as, properly implemented, it is the ‘earliest’ analogue signal in the chain and thus not impacted by any additional signal path such as the Fuze’s headphone amplifier stage. In the Fuze, it should be the signal which feeds the input of the headphone amp stage. The cheap electronics in the dock are irrelevant as they come after the line out stage and it’s up to you what standard of electronics you feed it into.

I would tend to agree with you, but the Fuze appears to be implemented differently.

axon

I have to agree with Skinjob and neutron_bob. The Fuze is implementing the line out in it’s own way. It should not be a concern about if it is a “true” line out or not. This was probably based on home stereo equipment with a 1volt peak signal. Are car stereos true line out with the 5volt pre-out signals?

The main thing is that there is a high quality, high impedance signal available to drive pre-in inputs harder than the headphone out. If I run the Fuze volume all the way to max, the signal is noticeably lower than with the Griffin Dock or the cable mod. The purpose of this project was to get a signal that is more useable with car stereos and line-in home equipment, as the headphone out does not drive them well. It seems to me that it works quite well without signal degradation, so I am happy with it.

If you are looking for audiophile quality, true to spec line out, you probably should not be using a compressed audio player anyway!

Hey,

Great work!

Just had a thought - wouldn’t it be nice to have a line in as well?

Pity you would have to muck with the firmware in order to get it to record.

Just an idea . . .

WR

@skinjob wrote:


axon01 wrote: 

I’m curious about what you said about the line out. I’m new here and haven’t found much information about the nature of the line out on the Fuze.  For instance, why does the line out need 3 volts?


 

The 3 volts is not on the line out itself, but is necessary to enable the line out.  Ordinarily, the dock would supply the 3 volts on a certain pin.  This tells the Fuzz it’s connected to a dock and should enable it’s liniment and disable it’s headphone out.

 

As to the other comments about SQ through the dock, it will be interesting to see how much difference there is between a simple cable with no extra electronics versus the dock where the signal passes through another circuit board.

Hi Skin and Neutron

It will also be interesting to compare the signals from a line out cable, a high quality dock and the headphone jack.

From what I am beginning to understand, the Fuzz is applying it’s amplification (or attenuation), digitally, through the chip, (thank you Neutron).  It makes sense then, that when the dock is deployed, the headphone jack is not, because the signal from the chip is routed to either the jack or the line out. 

The fact that you are able to get a signal from either the line out or headphone jack but not both and the position SanDisk placed the headphone jack, (intentionally precluding use while docking), seems to bear out that there are not two amplifiers, as I have read. 

The digital concept makes further sense because there is no distortion regardless of the volume level.  The interesting thing is that if Neutron’s supposition is correct,  that the gain is being applied digitally by the chip, the exact same signal would be available through the jack or the line out.   This, btw, agrees with what I heard when comparing the Griffin dock to the headphone jack.  The headphone jack, having less to go through, had the cleaner signal. 

More digital evidence might be when someone reported that when they used the remote on the sansa dock to change the volume, it did so by changing the volume on the Fuze.

axon

@14124all wrote:

I have to agree with Skinjob and neutron_bob. The Fuze is implementing the line out in it’s own way. It should not be a concern about if it is a “true” line out or not. This was probably based on home stereo equipment with a 1volt peak signal. Are car stereos true line out with the 5volt pre-out signals?

The main thing is that there is a high quality, high impedance signal available to drive pre-in inputs harder than the headphone out. If I run the Fuze volume all the way to max, the signal is noticeably lower than with the Griffin Dock or the cable mod. The purpose of this project was to get a signal that is more useable with car stereos and line-in home equipment, as the headphone out does not drive them well. It seems to me that it works quite well without signal degradation, so I am happy with it.

If you are looking for audiophile quality, true to spec line out, you probably should not be using a compressed audio player anyway!

Hi 14

This is really strange.  I don’t know why this was not what I found?  Fuze volume set to 100% gave me the same volume from the Griffin dock and the headphone jack.  I used an 18" Zu  Pivot (mini to RCA) to my M^3 and DT880s for the comparison.  

 

axon

 

Edit to add link:  What I used 

Message Edited by axon01 on 12-02-2008 11:29 AM

@axon01 wrote:


@14124all wrote:

I have to agree with Skinjob and neutron_bob. The Fuze is implementing the line out in it’s own way. It should not be a concern about if it is a “true” line out or not. This was probably based on home stereo equipment with a 1volt peak signal. Are car stereos true line out with the 5volt pre-out signals?

The main thing is that there is a high quality, high impedance signal available to drive pre-in inputs harder than the headphone out. If I run the Fuze volume all the way to max, the signal is noticeably lower than with the Griffin Dock or the cable mod. The purpose of this project was to get a signal that is more useable with car stereos and line-in home equipment, as the headphone out does not drive them well. It seems to me that it works quite well without signal degradation, so I am happy with it.

If you are looking for audiophile quality, true to spec line out, you probably should not be using a compressed audio player anyway!


Hi 14

 

This is really strange.  I don’t know why this was not what I found?  Fuze volume set to 100% gave me the same volume from the Griffin dock and the headphone jack.  I used an 18" Zu  Pivot (mini to RCA) to my M^3 and DT880s for the comparison.  

 

axon

 

Edit to add link:  What I used 

Message Edited by axon01 on 12-02-2008 11:29 AM

Hmm, not sure why you’re not hearing a noticable difference.  It’s fully expected that a headphone-out connected to a normal line-in will result in a low level.  The difference is usually very obvious.  Is it possible the line device you are plugging into has some kind of auto-sensing jack and is compensating for the headphone input?  A lot of newer devices that were designed with portable gear in mind handle headphone input better than devices designed for traditional home a/v gear.

axon01, take a look at the block diagram for the AMS AS3525 SOC. It may answer some of your questions. The system chip has 3 independent audio outputs on chip: headphone amp, line out and speaker amp. All of their inputs are driven by a common signal with the DAC and AGC limiter upstream. Easily manipulated digitally before the DAC output. Note that the line out output does not feed the headphone out input. This may clear up some confusion.

Google for AustriaMicrosystems AS3525 to find the function sheet and block diagram. Sorry, I do not have a URL handy.

WhiiteRaven, the AMS chip does have 2 dedicated line inputs. There most likely is no hardware connection on the Fuze board to the chip pins and no enable in the firmware. Maybe the next generation Fuze or another model will enable it. This chip is loaded with features that are not used in the Fuze.

@skinjob wrote:


@axon01 wrote:


@14124all wrote:

I have to agree with Skinjob and neutron_bob. The Fuze is implementing the line out in it’s own way. It should not be a concern about if it is a “true” line out or not. This was probably based on home stereo equipment with a 1volt peak signal. Are car stereos true line out with the 5volt pre-out signals?

The main thing is that there is a high quality, high impedance signal available to drive pre-in inputs harder than the headphone out. If I run the Fuze volume all the way to max, the signal is noticeably lower than with the Griffin Dock or the cable mod. The purpose of this project was to get a signal that is more useable with car stereos and line-in home equipment, as the headphone out does not drive them well. It seems to me that it works quite well without signal degradation, so I am happy with it.

If you are looking for audiophile quality, true to spec line out, you probably should not be using a compressed audio player anyway!


Hi 14

 

This is really strange.  I don’t know why this was not what I found?  Fuze volume set to 100% gave me the same volume from the Griffin dock and the headphone jack.  I used an 18" Zu  Pivot (mini to RCA) to my M^3 and DT880s for the comparison.  

 

axon

 

Edit to add link:  What I used 

Message Edited by axon01 on 12-02-2008 11:29 AM


 

Hmm, not sure why you’re not hearing a noticeable difference.  It’s fully expected that a headphone-out connected to a normal line-in will result in a low level.  The difference is usually very obvious.  Is it possible the line device you are plugging into has some kind of auto-sensing jack and is compensating for the headphone input?  A lot of newer devices that were designed with portable gear in mind handle headphone input better than devices designed for traditional home a/v gear.

Hey Skin and 1412

I ran some comparisons today in my office using the Griffin dock connected to the tape loop out on a mini component unit I bought in the 80’s.  There was no obvious difference between volumes of the headphone out jack and the dock jack, with the Fuze set to 100%. 

For some reason, I am not getting the expected results.  I had more than one person listen as I switched back and forth and no one seemed to feel there was an obvious volume difference. 

This bears out what I was hearing from my headphone amp at home. 

This is not the case, however, if the Fuze is set to less than 100% volume.  In that scenario, the dock is noticeably louder than the Fuze, by degrees, as the Fuze approaches 100% volume. 

I’ll try it again tomorrow, but I’m very confident in what I’ve heard, through both my headphone amplifier and now my office stereo.

I also discovered that (while listening to speakers), I was able to notice a slight increase in volume as I dialed up from 50% to 100% with the Fuze plugged into the dock.  This is not an obvious volume change, but it is detectable.  I only mention this because previously I thought there was no volume increase from 50% upward.

axon

axon, See what version firmware is on your player. If it is the 07 version try upgrading to the 11 version and retry your testing at 100% volume. I need to further test, but I have players with both versions and they do react differently. The volume control acts different when on my lineout cable between these 2 versions. I will verify with the Griffin Dock what happens (it should still be the same as my cable) and get back to this thread. I don’t use the current firmware version 15 due to playback problems encountered with it. Version 11 seems to work the best for audio playback, which is all i’m concerned with.

axon, WOW!!! Disregard previous post. There is a difference in firmware versions, but not with affected volume. What I found - You are correct!!! At 100% volume there is barely any differnce in volume output from the Griffin dock out or player headphone out. With my lineout cable there is a noticeable increase in volume! This renders the Griffin Dock rather useless as is for a lineout connection. This should be easy to alter the Griffin Dock to get the signal straight through. The Griffin Dock has series 220uf decoupling caps and parallel 10k impedance output resistors feeding the output jack. Time to bypass the resistors and maybe the caps!

NOTE: Another problem with the Griffin Dock is loss of the FM antenna. The player seems to only connect the FM antenna through the headphone jack common audio connection with no connection on the 30 pin connector. The Griffin dock has no connection for the antenna! Activating it will probably require an internal jump in the player to an unused pin on the 30 pin connector and a single wire to act as antenna on my cable. Getting the antenna to work might take some doing for other alternatives.

More finds! Sorry had a typo in the previous post. The output resistors are 100k not 10k. I disconnected them and had no difference in volume level, so it doesn’t seem to be impedance mismatch related. I’m going to reverse-engineer the Griffin board completely and come up with a full circuit diagram and hopefully see what is going on here. Since my cable does get a noticeable volume increase, it may be the voltage on pin7 may act as a gain control. Only speculation right now, I need to do more tinkering with the dock.

@14124all wrote:

axon, WOW!!! Disregard previous post. There is a difference in firmware versions, but not with affected volume. What I found - You are correct!!! At 100% volume there is barely any differnce in volume output from the Griffin dock out or player headphone out. With my lineout cable there is a noticeable increase in volume! This renders the Griffin Dock rather useless as is for a lineout connection. This should be easy to alter the Griffin Dock to get the signal straight through. The Griffin Dock has series 220uf decoupling caps and parallel 10k impedance output resistors feeding the output jack. Time to bypass the resistors and maybe the caps!

NOTE: Another problem with the Griffin Dock is loss of the FM antenna. The player seems to only connect the FM antenna through the headphone jack common audio connection with no connection on the 30 pin connector. The Griffin dock has no connection for the antenna! Activating it will probably require an internal jump in the player to an unused pin on the 30 pin connector and a single wire to act as antenna on my cable. Getting the antenna to work might take some doing for other alternatives.

Interesting.  I was going to get one of the Griffin docs while they were still on clearance, but if it doesn’t solve the level issue then there’s really no point.  Man, it really shouldn’t be this hard to get a decent line out.

I still haven’t had a chance to mod my cable, but I’m hoping to try this week.

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

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: