I'm thinking of buying a portable player (never had one before),
and here are a few questions to you, folks. What is your experience with your players:

1.
the battery in the HDD-based players (20 Gb)
All or most of them seem to have a "built-in battery". Does it mean it's not possible to replace it?

The batteries for laptops deteriorate very quickly after a couple of years, for example, a 3-hour battery will last less and less, all the way down to 15 minutes.
It would be very sad if a battery in the player died like this after just a year or two, and then what - to throw away the player because of the battery?


2.
The output power - how strong is it usually? Is it only possible to listen via those tiny earbuds or is it strong enough for the normal, bigger headphones?
Any difference between flash-players and HDD-players in this respect?
(I think I tend to listen at higher volumes, with classical music especially)


3.
if I want to connect the player to a stereo in the car, should I look for a player with any specific features? line-out? some native docking accessoiry should be available for the player?


4.
Does anybody know if the site dapreview.net is worth to read?
any reliable review sites out there?


that's all for now. perhaps I'll have more questions later...


thanks

1. I am interested in this too. Are there any harddisk-based players that do not require exotic batteries and still have an acceptable playtime? Does anyone have one?

2. My experience with my current mp3-player tells me the output is strong enough to use headphones. Volume will tend to be lower though, but still hard enough.

3. If you've got a line-in in your car-stereo you're perfectly set. You probably won't hear the theoretically loss of using your headphones out instead of a line-out in such a noisy environment as a car.

4. I don't know.

I only have direct experience with the iPod. You can replace the batteries on those pretty cheaply. For example: http://eshop.macsales.com/shop/ipod/batteryreplacement/ That site doesn't have any replacement batteries for the newest iPod revision yet, but if experience is any guide, they should be along shortly.

All of frodoontop's other answers also apply to the iPod.

It is possible to replace the battery on some HD players -- it depends on finding the right size/type battery to fit. If you do not mind opening up and doing some soldering, it's an option.



I don't know. We can only speculate. But consider that usually you can send in the player and have the batter replaced for about $100USD. In any case, it seems like a very low respect for the consumers to use non-user replacable batteries in products such as this.




As a general rule, the maxmum output voltage is limited by the power supply voltage, and can be calculated from that. However, if a special circuit called a DC-DC convertor is used, this can be potentially increased. I have not measured the output voltage on various portables. Only on my ZenXtra. It does not even reach the calculated max. output voltage based on battery voltage limits. It seems to be limited artifically. For example, it can output a measured 0.86VRMS. It has a 3.6 VDC battery. It should be capable of 1.27VRMS when fully charged based on 3.6VDC[(VDC/2)0.707=VRMSMAX]. So, you can't even base what the maximum output will be based on supply voltage.

BTW, I don't think you will find any that will provide enough voltage for a Sennheiser HD650, for example. Something like that needs around 2.0 VRMS, or more if very dynamic source material is used.




Line out is not important. The headphone out IS a line out. Just one with adjustable volume. As for docking stations, that is a personal preference that only you can answer.

-Chris

Chris, this is another thing I always wanted to know - what is the limiting factor here: is it the high "Nominal Impedance" (300ohms for HD650) or is it possibly low "sensitivity" (which I read is sometimes given in dB/mW) ?



Otherwise, thanks everyone for your answers. In the meantime I've been doing some internet research myself too. The options seem more clear now.

Now I'm considering this 20 Gb HDD player: Archos Gmini XS 202. More photos here
Advantages (for me):
* no special software needed to upload files, can handle directories too
* flexible navigation and display both by filenames and by id3 tags
* No video - cheaper price.
Possible drawbacks:
* built-in battery (Archos can replace it for a reasonable price if you send them the unit. Also I see similar older models have cheap 3rd party batteries available. Don't know how tricky it is to replace it myself)
* one person reported the LCD screen was easily broken
* no FM radio

The problem is both. A headphone jack[if properly designed] will function correctly if the headphone is 30 ohms or 300 ohms. It will produce the same voltage[within a percent or so difference] into either impedance[assuming it's a low source impedance headphone amplifier design, which is most of them]. Current is not a problem on any properly designed headphone amplification circuit. The only issue of importance[with a proper designed headphone amp stage] here is voltage. If you have headphone A with 30 ohms nominal impedance and 98db/mw sensitivity it may operate just fine with X VRMS max. available. However, take that same 98db/mw sensitivity and apply it to a 300 ohms nominal impedance load and call this headphone B. This will not operate at sufficient SPL with X VRMS. The 98db/mw only refers to POWER EFFICIENCY. It is a very poorly chosen specification for headphone senstivity, because power requirement of a headphone is almost never an issue, even on portable audio players. You can not discern if a headphone will work at sufficient SPL by referring to the dB/mW of the headphone and then referring to the mW output spec of the headphone line. The issue that is relevant is VOLTAGE EFFICIENCY. Headphone B is not going to have sufficient SPL, because while it needs the same amount of power as headphone A, it needs much more voltage to reach the same SPL. It needs less current than headphone A, but it also needs more voltage -- senstivity should be rated with voltage, not power, for headphones. In this proposed hypothetical circumstance, you have a situation where the headphones require the same power(V*I=P) but that power can NOT be developed into the higher impedance due to voltage limitations of the amplification. You will have to compensate for the use of dB/mW ratings on headphone by calculating the required voltage, basing this on the nominal impedance and dB/mW rating. To do this accurately, you need to use a headphone with a known sensitivity and impedance and determine a baseline in relation to available gain/voltage. But this is hardly of any help without knowing the voltage output of a specific product, but you can estimate based on typical performances. I would say that under 1VRMS is expected typical for portable players. It should be noted that you will run into two different problems depending on if you discussing gain or voltage limitation. If your portable player simply does not get loud enough, then it will not usually clip -- the egineers have designed it so that maximum gain at 0dBFs[maximum relative value in digital signal] will never exceed the amplified rail voltage. However, if using a battery powered portable amp, no such limitiation will probably exist. You could have insufficient voltage but sufficient gain. This would mean that for most of the time, the nominal signal level of the music would sound okay, as it is operating within the voltage envelope of the available power supply, and the gain is sufficient to have good SPL. However, on dynamic peaks the gain would be too high for the available voltage, thus voltage limit induced clipping[and dynamic compression] would occur as the input signal, factored by X gain amount, required higher voltage then was available to remain at X gain amount. Result: chopped off waveform peaks.

-Chris

Thanks, Chris!

OK, so I'll have to try my headphones with the player and see what loudness they can produce without clipping. Maybe I'll have to buy the in-ear phones after all. we'll see...

Two things :
1) your calculation is flawed when calculating the potential output based on battery voltage. A typical push-pull output stage loses about 0.6V in each of the two output transistors if they are bipolar types (usually they are) so you need to deduct 1.2V from the supply before your calculations. A 3.6V battery means about 2.4V peak-to-peak output, so the RMS value would be 2.4 / 2 x 0.707V. i.e. 0.85V, which is very close to your measured 0.86V. For a headphone of 16 Ohms that equates to only 45mW power. FET output transistors (less common in small output stages) drop a variable voltage depending on the load and can, theoretically, reach supply voltage on infinite load impedance. All this depends, as you rightly point out, on there being no DC-DC converter in use.

2) A headphone output actually isn't a line out. Line out, according to the hi-fi industry "standards" is 0.775V RMS. You can generally use it as one though and I often connect headphone outputs from portables into the line-in of an amp.

Shoot me if ya like, but we use a cheap RCA branded cassette adapter, and have no issues with the sound quality other than reripping all the stuff my wife did at 128k for her old Rio.

We mostly use a Archos 20, now about 3 years old, takes 4x normal AA NiMh batteries which we recently replaced for the first time while swapping in a 80 GB drive.

We have several sets of earbuds and various other headphones, with Sennheiser MX400 used the most with all portables and plenty loud.

****************** Issues I didn't see mentioned that I found important.

Is the device proprietary, ie somebody else controls my music and what I do with it.

Or does the device just look like a normal hard drive to my PC and I can freely move ANY files I want back and forth, with no special music file formats required.

Does it include tetris that can be played while listening to music?

Thank you for pointing out this detail. Then I guess the Zen is producing it's maximum possible voltage without artifical limitation. Is this also a typical drop for the standard configuration op-amp based amplifiers as opposed to discrete designs?



It may not be line out by this standardized definition, but it can serve an identical purpose, and that is what I intended to state.

-Chris

It doesn't make any difference whether an amp is discrete components or not, the output transistors use the same principle of operation and the voltage drop will be the same, give or take. That's true for bipolar transistors in general, they have about 0.6V across them when "saturated". FET transistors are a different matter, they act more like a resistor, so the voltage drop depends heavily on the load current.

Regarding the line-out, you are of course quite right about using a headphone out as a line-out (usually anyway!). My reply wasn't meant contradictively :-)

Some HDD players have replaceable ones (as in you can easily open the back and put in a new one, usually the bateries are 40$ on their site) and some (like the ipod) need you to send it in and they will charge you 100$ to replace it.



You could get a casette adapter, or a radio transmitter. Both can plug into your headphone jack.

Line out bypasses the player's amp, whereas headphone out does not. Therefore, line out has the potential to provide a cleaner signal.

Has anyone compared the signal quality between the two when the signal is fed into a home or car stereo? Is there a noticeable difference? I am considering the Cowon iAudio X5 because it has very good audio specs and has a line out, but I am also wondering if I am overemphasizing the importance of having a line out.

What is the difference? The output from the DAC is buffered(this is basicly an amp stage) before being sent to an external output jack, even on a 'line out'. Perhaps there is yet 'another' amplification stage after the buffer on devices that feature both a line out and headphone out, but even if so, there is not reason for it to degrade the signal in any appreciable degree unless it is just a bad circuit design. On a device without a line out, I fail to see a distinction except that it has a volume control adjustment added.



My ZenXtra performs perfectly(no audible noise, even on very efficient Sony MDR-CD3000 headphone, distortion products well below audible thresholds, frequency response is very flat), it has no line out. Since it does not degrade the signal in any appreciable manner, I can not imagine how a 'dedicated' line out would benefit the performance of any device over what a headphone output can do.

-Chris

Strictly speaking, he's right about a line-out having the potential for a cleaner signal since it doesn't go through the power-amp stages required for a headphone output. Generally, a line-out tends to be connected to the "live" end of the volume control for the output amp.

In reality, however, the output amp should not add any distortion or noise that would be audible unless it's very, very poorly designed. Actually I have a Sony Discman of a few years vintage. It has line-out and headphone-out and the line-out is significantly cleaner because the output amp clearly has problems. It buzzes due to a digital signal bleed somewhere, probably in the power supply or from lack of screening.

I am a bit confused by your reply to me in this case because it seems as if you just agreed with everything I said.

WmAx: "What is the difference? The output from the DAC is buffered(this is basicly an amp stage) before being sent to an external output jack, even on a 'line out'. Perhaps there is yet 'another' amplification stage after the buffer on devices that feature both a line out and headphone out, but even if so, there is not reason for it to degrade the signal in any appreciable degree unless it is just a bad circuit design. On a device without a line out, I fail to see a distinction except that it has a volume control adjustment added."

-Chris

OK, I'm satisfied. With a high-quality device, line out is not essential, as it will be virtually identical to the headphone out in terms of sound quality. Thanks.

- Brad