Question about the iPod/USB option. Please help.

[vanbmw]

The gap between songs is about the same as you would find on a CD. I do not know if that can be changed or modified. It is very fast to access the songs and the menu is very easy to use. You can load songs or jump between songs faster then on a CD. I just have the base 135 stereo.

[jeremyc74]

Originally Posted by clived

Jeremy, can you exaplain how the docking connector and the headphone jack use exactly the same signal when the former is not attenuated by the latter's volume control.....?

If you can't hear a difference, that's finr, but it doesn't make the blantantly untrue correct ;-)

Sure I can explain it. When you plug something into the min-jack, the volume control is set to a specific volume that matches a line output, because all the thumbwheel controls are disabled.

Do you seriously thing they're using a different D/A converter and amplifier for each one? :iono:

[clived]

No, I'm not saying they use a different D/A - where do I say that....?

You're saying that the output from the docking connector and the output from the headphone socket are *exactly* the same. I'm saying that they are not - if nothing else, the connectors, the signal path proximity to noisy digital circuitry, the circuit board traces and any cabling that carry the signal to and out of each output are different and will be subject to different levels of interference, impedence and colouration. These are not *exactly* the same, and the way those changes interact with the myriad different loads that various headphones and pre-amps present can't really be predicted.

Whatever the reason - be it an alledged additional headphone amp in the jack plug output circuit (many sites talk about this, but I've never seen an iPod schematic, so I'll reserve judgement on that) or some combo of the connector / path stuff I've outlined below, I do know the outputs sound different.

Very happy to agree with you that my "different" is your "pretty much the same" or that any difference I hear as "better", you'd consider "worse". But I won't agree that both outputs sound exactly the same.

[john970]

Originally Posted by jeremyc74

Audiophile and IPod don't belong in the same sentence together to begin with, but the mini-plug and the headphone jack on the IPod use the exact same output signal. There's no way ANYONE will ever convince me the mini-jack provides a better connection, or that you're going to be able to hear a difference between 6 inches of headphone cable.

This comes up about every two weeks and no one seems to want to search on this. The line out and headphone jack do indeed share the same signal path, and the dac used in most ipods is very good.

There is probably as much info on this in this forum than any audio forum, if you can find it.

[john970]

Originally Posted by clived

No, I'm not saying they use a different D/A - where do I say that....?

You're saying that the output from the docking connector and the output from the headphone socket are *exactly* the same. I'm saying that they are not - if nothing else, the connectors, the signal path proximity to noisy digital circuitry, the circuit board traces and any cabling that carry the signal to and out of each output are different and will be subject to different levels of interference, impedence and colouration. These are not *exactly* the same, and the way those changes interact with the myriad different loads that various headphones and pre-amps present can't really be predicted.

Whatever the reason - be it an alledged additional headphone amp in the jack plug output circuit (many sites talk about this, but I've never seen an iPod schematic, so I'll reserve judgement on that) or some combo of the connector / path stuff I've outlined below, I do know the outputs sound different.

Very happy to agree with you that my "different" is your "pretty much the same" or that any difference I hear as "better", you'd consider "worse". But I won't agree that both outputs sound exactly the same.

Sorry to burst your bubble, but both outputs sound exactly the same provided the volume is set to the same level as the fixed out on the line out.

[john970]

Originally Posted by jeremyc74

Sure I can explain it. When you plug something into the min-jack, the volume control is set to a specific volume that matches a line output, because all the thumbwheel controls are disabled.

Do you seriously thing they're using a different D/A converter and amplifier for each one? :iono:

+1

[john970]

Originally Posted by arrons1969

Yeah, the problem with the IPod is that the sound is played over the stereo headphone socket out of the Ipod, which is already amped, then into the system. The USB port is ONLY used for Command and Control. Assuming the MP3 decoder on the HU of the system is any good, then keeping the signal digital from the USB port, then decoding it on the HU should produce a cleaner sound, with no preamp issues or interferance while in the analogue transmission.

The only reasons you need the stupid split cable is to allow you to play itunes DRM crap, and for playlists if you use them. I think it's better to rip to MP3, and avoid DRM. But if you buy all your music from itunes ... well you've got no option. Die DRM ... Die !!!

Wow, people are actually using their brains in this thread. This is mostly correct but let me clarify a few things and take it a step further...

The only difference is you are using the DAC in the head unit in place of the ipod's DAC, which based on info we have on the headunit dac (none) might be better or worse. The amp in the ipod, when set to a resonable level (like in the line-out) shouldn't introduce any detectable distortion (unless you have an oscilloscope).

It's funny to me people will spend hours and hours on this .0001% stuff, and then listen to a 40kbps Sirius or XM stream and say it sounds good.

[jeremyc74]

Originally Posted by john970

This comes up about every two weeks and no one seems to want to search on this. The line out and headphone jack do indeed share the same signal path, and the dac used in most ipods is very good.

I didn't mean that as a dig on the Ipod from a hardware point of view, but the compressed data format it's playing.

Personally I don't have any issue with the sound from an MP3 player (the higher the bit rate the better obviously), I just think a lot of people take things way to far when dealing with signal cables and such. :w00t:

[john970]

Originally Posted by jeremyc74

I didn't mean that as a dig on the Ipod from a hardware point of view, but the compressed data format it's playing.

Personally I don't have any issue with the sound from an MP3 player (the higher the bit rate the better obviously), I just think a lot of people take things way to far when dealing with signal cables and such. :w00t:

Yeah, it's voodoo. Like pear audio and "shielded" optical cables.

Some of the DACs/amps in portable electronics are crap though, just not in most ipods. An iPod can also play apple lossless, but I did a blind test and I can't tell the different on my high end home system (B&W/Denon/MIT) so I use 256K AAC now.

[jeremyc74]

Originally Posted by john970

Yeah, it's voodoo. Like pear audio and "shielded" optical cables.

I stopped reading one particular magazine back in the day when they claimed to be able to hear the difference between two quality fiber optic cables, claiming one sounded "warmer" than the other. Total BS.

[john970]

Originally Posted by jeremyc74

I stopped reading one particular magazine back in the day when they claimed to be able to hear the difference between two quality fiber optic cables, claiming one sounded "warmer" than the other. Total BS.

My favorite is "more musical". WTF?

[clived]

Originally Posted by john970

The line out and headphone jack do indeed share the same signal path

If the jack socket is on the top of the iPod and the docking connector is on the bottom, how on earth can the signal paths be the same?

Same DAC, obviously. Same signal path? Well, we must have very different definitions of signal path

[clived]

Guys, so, this whole conversation was *issing me off a little as, well, I knew I was right. And now I shall prove it.

Originally Posted by jeremyc74

Sure I can explain it. When you plug something into the min-jack, the volume control is set to a specific volume that matches a line output, because all the thumbwheel controls are disabled.

This, simply, is not correct, I've just tried it. I used the following:

1) My Gen 5 iPod
2) The Russ Andrews docking connector -> mini jack cable, connecting the iPod to a small set of portable powered speakers
3) A "Monster" iPod AV cable to connect the headphone socket of the iPod to my home AV system.

If what Jeremy says is correct, using both outputs at the same time would result in a) the volume being set to something specific, b) the thumbweel controls being disabled and therefore c) the same, fixed, level coming from both outputs.

None of this happened.

The output, as expected, from the docking connector is fixed. The output from the headphone socket can be changed from nothing to maximum using the thumbwheel. The output from the docking connector remained the same at all times.

This proves that there is seperate processing going on in the headphone output signal path and the signal paths are not "exactly the same".

As my barrister friends would say, I rest my case :wink:

Of course, I respect that some of you may not be able to hear any difference between the two outputs, but at least now we can agree that you're not hearing processing that is happening, not processing that isn't

[john970]

Originally Posted by clived

Guys, so, this whole conversation was *issing me off a little as, well, I knew I was right. And now I shall prove it.



This, simply, is not correct, I've just tried it. I used the following:

1) My Gen 5 iPod
2) The Russ Andrews docking connector -> mini jack cable, connecting the iPod to a small set of portable powered speakers
3) A "Monster" iPod AV cable to connect the headphone socket of the iPod to my home AV system.

If what Jeremy says is correct, using both outputs at the same time would result in a) the volume being set to something specific, b) the thumbweel controls being disabled and therefore c) the same, fixed, level coming from both outputs.

None of this happened.

The output, as expected, from the docking connector is fixed. The output from the headphone socket can be changed from nothing to maximum using the thumbwheel. The output from the docking connector remained the same at all times.

This proves that there is seperate processing going on in the headphone output signal path and the signal paths are not "exactly the same".

As my barrister friends would say, I rest my case :wink:

Of course, I respect that some of you may not be able to hear any difference between the two outputs, but at least now we can agree that you're not hearing processing that is happening, not processing that isn't

Sigh...

I believe what was meant by signal path is that it goes through the same dac, the same capacitors, and the same opamp stages. Both jacks produce output that has gone through the opamp stage with different output voltage (unless the volume is set to the same level as the line out, in which case they would be literally identical).

So if you can hear a difference, it is in your head. Wolfson (Apple's supplier for most of the iPod audio components) publishes their circuit boards online, you can google the 4th gen dac/opamp boards and see for yourself.

There is a company called Red Wine Audio that will crack open the case and solder on some leads so you can get a true line out from it, but I doubt anyone would be able to tell the difference.

[jeremyc74]

Originally Posted by clived

Guys, so, this whole conversation was *issing me off a little as, well, I knew I was right. And now I shall prove it.



This, simply, is not correct, I've just tried it. I used the following:

1) My Gen 5 iPod
2) The Russ Andrews docking connector -> mini jack cable, connecting the iPod to a small set of portable powered speakers
3) A "Monster" iPod AV cable to connect the headphone socket of the iPod to my home AV system.

If what Jeremy says is correct, using both outputs at the same time would result in a) the volume being set to something specific, b) the thumbweel controls being disabled and therefore c) the same, fixed, level coming from both outputs.

None of this happened.

The output, as expected, from the docking connector is fixed. The output from the headphone socket can be changed from nothing to maximum using the thumbwheel. The output from the docking connector remained the same at all times.

This proves that there is seperate processing going on in the headphone output signal path and the signal paths are not "exactly the same".

As my barrister friends would say, I rest my case :wink:

Of course, I respect that some of you may not be able to hear any difference between the two outputs, but at least now we can agree that you're not hearing processing that is happening, not processing that isn't

I don't have the equipment to test this, but if you say so, I'll believe it. So there is an attenuation circuit on the headphone output that isn't on the mini-connector.

I don't believe however that you can hear the difference in a couple of inches of copper signal trace on a circuit board, and I never will.

[clived]

I notice my question has somewhat been avoided. Jeremy very explicitly stated that "When you plug something into the min-jack, the volume control is set to a specific volume that matches a line output, because all the thumbwheel controls are disabled".

This is the point I was responding to and I'd like to see Jeremy comment.

However John, you're making a lot more sense and I understand you description of the op-amp path being the same for both outputs - and this explaination isn't inconsistent with the observed behaviour, unlikely Jeremy's theory.

I'm therefore wondering how much of the differences heard are down to cabling - I'm certainly not using exactly the same cables (or, obviously connectors) for both connection types - for docking connector it is Kimber and for headphone it is a different Kimber or Monster. Or do you not beleive that cables can have their own influence on sound?

[jeremyc74]

Originally Posted by clived

I notice my question has somewhat been avoided. Jeremy very explicitly stated that "When you plug something into the min-jack, the volume control is set to a specific volume that matches a line output, because all the thumbwheel controls are disabled".

This is the point I was responding to and I'd like to see Jeremy comment.

?

I commented specifically on that. I said I don't have the equipment to verify it, so I'll take your word for it. I also conceded that there is an attenuation circuit in the headphone line out if what you are saying is true. What question exactly would you like answered?

As for the cables, NO, I absolutly don't believe that you can hear the difference between two 6 inch audio cables of reasonable quality.

[john970]

Originally Posted by clived

However John, you're making a lot more sense and I understand you description of the op-amp path being the same for both outputs - and this explaination isn't inconsistent with the observed behaviour, unlikely Jeremy's theory.

I'm therefore wondering how much of the differences heard are down to cabling - I'm certainly not using exactly the same cables (or, obviously connectors) for both connection types - for docking connector it is Kimber and for headphone it is a different Kimber or Monster. Or do you not beleive that cables can have their own influence on sound?

I would do a blind test - you would be surprised how different the results can be.

Connection types and how they are soldered to the wires can have some effect, but not the cable. Line out / headphone signals are in the vicinity of 1 volt RMS at 1W. I would make sure you keep all cables away from any power cables, and anything wireless (especially cell phones). This has been an issue for me as my computer and wireless router are in the same vicinity as my stereo, so I try to keep all my interconnects optical and I have some MIT speaker cables with giant filters on them. High end interconnects usually have more flexible casing though. If you crack open a high end receiver or speaker you'll find the interconnects/wiring inside the unit are just unshielded soldered copper or even PCB traces. Come to think of it if you crack open that dock of yours you might be surprised at what you find...

It should say a lot about any of their cables when companies advertise performance advantages for digital cables when most of the digital protocols have error correction built in (HDMI comes to mind).

[john970]

Originally Posted by WhiteOne

Doesn't USB+thumbdrive sound much better than using an ipod?

No.

[clived]

Jerermy, I started writing my response before you'd replied (check the close timestamps) I don't think there is an attenuation circuit in the headphone side of the house that isn't also in the docking connector side - I think John is correct re the twin op-amp topologym which is why we're on the cable discussion ;-)

[john970]

For those interested, here is the chipset (dac, amp, mixer, eq, etc.) used in most iPods and every detail you could possibly want.

http://www.wolfsonmicro.com/uploads/.../en/WM8750.pdf

[taiheung]

Originally Posted by elp_jc

Thank you very much for your help folks. I guess I can figure that out. Let me just summarize what I need to do:

Download the latest version of the Windows Media Player, and try to 'load' my CDs into MP3 files, then record the files into folders (a CD per folder, maybe?) on 'my documents', and finally dragging the folders into the USB drive? Please let me know if I'm missing a step.
I guess I should be able to figure out how to do that. Thank you very much.
JC

While you're at it though, upgrade that USB stick. You can get some ridiculous sizes now - and if you want to make 1 permanent usb stick with all your music from forever (at 46 you must have a fair collection, hehe) then bump up your memory size.

Get one chunky one and never buy another again.