[younglu]

thanks you all

2 Deuce_Bigalow,
my pana is about 1996 version,max output volt 0.7Vrms(with 50kohm impandence),5mW(16ohm imp.) is for sure which maybe is unbelieveable. it's old one.

but it's sound quality and music taste is much finer than sony ones .(i have listened so many sony ones).

so,that's the reason i keep using it.(once,i thought to buy a sony latest version of portable,but i considered that is not worthy. To upgrade my headphone is a much brighter way.)


2 MacDEF,
why outputting additional several 10mWs will cause the bettery-life shortened---------it's just several 10mWs.

thanks blr,
you're right, i've found on the Grado's homepage that the Grado SR40 is made in China which gets the driver from SR60.
also,the price is not very important for me. i do not want to buy a cheap but with poor sound one(portable player and headphone both).

 

[younglu]

yes,the sensitivity is more important than just impandence.at least for me.

it's right,amp it,it's a fine good sound source,the need for amplifying it to upgrade the sound-quality level is a must.


any you good advisor could you share experience to suggest a amp for this pana?

 

[MacDEF]

Quote:

why outputting additional several 10mWs will cause the bettery-life shortened---------it's just several 10mWs.

It's a constant flow of twice the output -- a 10mW x 2 headphone output will significantly reduce the battery life of a portable over a 5mW x 2.

 

[Joe Bloggs]

??

I would have thought it is possible for the pcdp to lose energy through the headphone jack when there's something plugged in, and hence a complete circuit for current flow!

Also, does the power consumption remain the same no matter what the volume of the music you're playing??

 

[MacDEF]

Quote:

Also, does the power consumption remain the same no matter what the volume of the music you're playing??

Nope; the louder you listen, the shorter your battery life.

 

[Joe Bloggs]

Yeah, that's my point! I thought that the power rating of headphone outputs is just the *potential* power output--it would only give out as much power as your headphones need to drive out your music at the desired volume, and craps out when the headphones are asking more than it can give. So a higher-power headphone amp shouldn't mean high battery drain unless you're driving your phones louder or a lower-power amp doesn't have enough power to drive the phones...

I suppose it's an issue of efficiency?

 

[MacDEF]

Basically, unless you have VERY efficient headphones, your headphones will use more power driven by a 10mW amp than driven by a 5mW amp at the same apparent volume. They will also sound a better, since they will be able to get a bit more of the power they need to sound their best.

 

[Eagle_Driver]

And not all low-impedance headphones are efficient! In fact, I am using a Sony D-EJ721 PCDP with two 850mAh NiCD AA batteries and with its digital volume control set at 27/30 to test out the effect of headphone impedance on battery life. My first test is with my 16-ohm Sony EX70LPs (so far, the batteries haven't yet pooped out on me - and I had started this test just over 16 hours ago); my second test, with my 120-ohm Sennheiser HD 590s (which sounded about as loud as my EX70s at the same volume control setting).

 

[Joe Bloggs]

You use the D-EJ721 to drive the HD590???

 

[Apheared]

your headphones will use more power driven by a 10mW amp than driven by a 5mW amp at the same apparent volume

Nope... it could be 105mW or 5mW _capable_ but at the same apparent volume it's a toss-up which will use more current. The quiescent current will be specific to the amplifier chip used... and I doubt you'll go much beyond that at sane human volumes. The volume at the same level on the same phones will require the same amount of voltage (implying the same amount of current)

This is where sensitivity comes in; a 120 ohm headphone can actually sound louder than a 32 ohm headphone at the same voltage... even though the 32 ohm will eat up 4x more current... if the 120 was that much more efficient than the 32.

 

[Eagle_Driver]

Quote:

Originally posted by Joe Bloggs You use the D-EJ721 to drive the HD590???

Though I don't recommend using expensive headphones directly from crappy headphone op-amps! With those Sennheiser HD590s, I can easily tell the difference between the Sony D-EJ721's headphone op-amp and the Panasonic SL-CT470's headphone op-amp. The CT470's op-amp definitely sounds louder and more dynamic than that of the D-EJ721 (which sounds flat and lifeless compared to the CT470).

 

[Eagle_Driver]

With 16-ohm Sony MDR-EX70LP: 17.8 hours
With 120-ohm Sennheiser HD 590: 17.5 hours

Both results were based on two 850mAh NiCD RadioShack "original" 23-149 rechargeable batteries; the currently available version of those batteries are now rated at 1000mAh.

Well, that means little or nothing as far as battery life when using small earbuds versus full-size circumaural headphones of the same voltage sensitivity - the batteries may have been charged fully when I tested with the EX70s, but may not have been charged fully enough when I did the same test with the HD 590s. Thus, the results could have gone either way.

Conclusion: A statistical tie.

 

[younglu]

good objective test,thanks Eagle_Driver.

it's just like what i wondered and thought about-----with some 10mWs' output increasement will not signifcantly decrease the bettery life.