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What kind of power supply will you like to see in our flagship portable amp E12. - Page 2  

Poll Results: What kind of power supply will you like to see in our flagship portable amp E12.

Poll expired: Aug 10, 2012  
  • 32% (8)
    A. 6 AAA li-ion batteries, Supply Voltage: +/- 11V
  • 60% (15)
    B. Build in 11V battery, Supply Voltage: +/- 11V
  • 8% (2)
    C. Build in 3.7V battery, Supply Voltage: +/- 7.4
25 Total Votes  
post #16 of 22
Quote:
Originally Posted by tzjin View Post

Guys, just count the stars. tongue.gif

A has 10, B has 11, C has 12.

 

 

 

In all seriousness A will be extremely inconvenient. B would be my default, while C would be my top choice if you find there is no significant degradation of sound quality.

you forgot to add weighting to each cat assuming SQ =3 Con=2 Price=1

A =23, B= 24.5, C= 24.5

 

Assuming SQ = 3 Price= 2 Con=1

A=22 B= 23.5 C= 23.5

 

If it comes down to this, I rather choose B. But man FiiO, 2x3.7V no conversion true bipolar!!!

post #17 of 22

As always, we're so behind when it comes to storing energy.  There have been like little to no advances. 

 

It's hard to choose really.  I'm not too happy with any of those.  I'd just say whatever is best quality and can be charged through USB and/or doesn't need to be taken out to charge.  If that's not possible than it's too early in time to make such a product.  It's too much for people to want to deal with.  It's too much nuance for a mere amp that in itself would be considered an inconvenience to some.  That's not my understanding, but comfort for something of this nature is the name of the game.  Since quality is sacrificed to such a degree, it's not worth it unless a good compromise can be found.

 

If I had to choose, I'd say B.  Sucks that it's such a difficulty.  I feel for you guys at FiiO and your ambition.


Edited by Typhoon859 - 8/3/12 at 3:16pm
post #18 of 22
Quote:
Originally Posted by Tilpo View Post

The +- 7.4V should be good enough for most headphones.
Let's just take the HD650 as a random example. With a bit of headroom, the reproduced waveform should have a maximum of at least +- 6.5V, that's 9.2V RMS.
The HD650 is rated 103dB at 1V RMS, giving 122dB SPL at 9.2V RMS. That's ear shattering loud.
The HD650 has a rated nominal impedance of 300ohm, which gives us 282mW, this is in fact well above the maximum rated power of the HD650; 200mW.
I think loudness is more than adequate with rail voltages like that on most headphones.
Then the next concern is the quality of the power supply. Putting 6 batteries in series should reduce variation in the rail voltages. But as far as I know most batteries are already pretty darn smooth.
Additionally, and note that I'm no expert on this, a well designed circuit should be able to have a power supply rejection ratio big enough to make the variations in rail voltage that are already small, too small to be audible.
The final point is battery life. I personally think this is more important than that extra 3.4dB SPL. (20*log(11/7.4))
I have no idea how this is better or worse with the 3.7V battery. You'd have to fill me in on this. As well as charge time, but I imagine that option A and B charge faster due to the bigger voltages of the charger (USB voltage is low).
Something I almost forgot, but will option C use the same trick to double the rail supply as the Mini3? That is, an active ground channel? That was the biggest critique on the Mini3, and I would imagine it does indeed affect sound quality. If this is indeed the case, then option B may be a better choice after all, but note that I'm no expert on this.
Finally add in the huge convenience of option C's USB charging. I personally think this is an absolutely huge advantage that should not be underestimated. And especially the inability of option A to be used during charging is a very large minus. I think that it makes option A too inconvenient to be considered. Isn't it possible to change the circuit such that some of the DC adapter's power goes towards the audio circuit as well as charging?
All in all, I think option C is the best, but it does depend on how much sound quality is sacrificed.
Please point out any mistakes I made regarding circuit design, since I am only learning.

 

Even assuming 6.5V peaks (13V peak-to-peak) from 7.4V rails, that gives 4.6V rms, not 9.2V.  rms value is not going to be higher than the peak value (I think you multiplied by sqrt(2) rather than divided, where sqrt(2) comes from us assuming a sine wave.)  Granted, that's more than most people need for most headphones.

 

Mini3 does not double the supply rail.  It splits the ~9V from a 9V batteries in half, for ±4.5V rails.  Hopefully my memory is not failing me on that point.  (Other single-battery amps like some CMOYs use a rail splitter but skip the active ground.)  To double the voltage, you need to do DC-DC conversion or implement a charge pump to generate an effective negative rail from the positive one.  The TPA6130 handling the output on the E5 / E6 / E7 has a charge pump internally.

 

 

Quote:
Originally Posted by firev1 View Post

  Come on Fiio, 2 x 3.7V lithium! I know you can do it! 

 

As long as the amp has enough current,  even 7.4V should be more than enough for portable use. Lithium ions have pretty high discharge rates though so its good. Dacport may run 18v but does the usb bus provide enough current? 5V 500ma usb 2.0 is barely enough for some applications(not enough headroom for the focusrite preamps I borrowed recently) and the DACport is running at +/-18V. Frankly I expect the E12 not to be Class A design since if it is, I think it would be promoted in front. I expect a less energy wasting Class B amp instead.  Of course I could be wrong.

 

Frankly I don't expect E12 to do orthos but most dynamics and especially IEMs.

 

Well, one clear issue with ±3.7V is that not many chips operate (well) on such a low supply, and that would result in lower power output than the E11.  Somehow I don't think that's going to fly.

 

 

 

I voted for B, though if you can get C to work, that would be okay too.  First of all, I think that having an amp that can't be used while being charged, like the E11, is a bad idea.  But if you actually need to take the batteries out to charge them, that's just going to wear out the battery compartment, create more potential points of failure, and so on.  Not to mention:  wearing out the user.

 

But maybe my idea of the E12 is not as a (relative) flagship portable amplifier, but as a missing link in the product stack.  FiiO E9 has both noise and output impedance that are too high for certain headphones, E5 / E6 are great for the price but are not powerful enough for many headphones and have borderline specs, and E11 can't be used without needing to charge and unplug it.  My hope is that the E12 can be recommended for having low noise, low output impedance, desktop operation without needing to unplug it, portable operation, and enough power for many common headphones like Sennheisers, 250 ohm Beyerdynamics, and so on.

post #19 of 22
Quote:
Originally Posted by mikeaj View Post

Even assuming 6.5V peaks (13V peak-to-peak) from 7.4V rails, that gives 4.6V rms, not 9.2V.  rms value is not going to be higher than the peak value (I think you multiplied by sqrt(2) rather than divided, where sqrt(2) comes from us assuming a sine wave.)  Granted, that's more than most people need for most headphones.

Mini3 does not double the supply rail.  It splits the ~9V from a 9V batteries in half, for ±4.5V rails.  Hopefully my memory is not failing me on that point.  (Other single-battery amps like some CMOYs use a rail splitter but skip the active ground.)  To double the voltage, you need to do DC-DC conversion or implement a charge pump to generate an effective negative rail from the positive one.  The TPA6130 handling the output on the E5 / E6 / E7 has a charge pump internally.
I see, thank you for pointing out my silly mistake regarding RMS voltage. For some odd reason I used an amplitude of 13V, but that's peak-to-peak.

It just doesn't stop with the mistakes does it?
You're right in pointing out that the Mini3 splits the rails. My lack of knowledge of electronics makes me jumble things around sometimes.
However, I do hope that the E12 doesn't use an active ground, since I have heard a lot of critique on that point (not just from Voldemort, also from others)
post #20 of 22

-


Edited by firev1 - 8/3/12 at 9:55pm
post #21 of 22
Thread Starter 

OK, Thank everyone who voted the battery of E12. we will choose a build in 11V li-ion battery solution, and it can be charged during listening, and we will see if we can  make it charged by a USB ports.

post #22 of 22
Charged during listening, OH YEAH!
biggrin.gif
Thanks for being awesome FiiO, and for making my firs standalone headphone amp. I think I will wait for this E12, but please make it right! Don't rush out anything unfinished like game companies do these days!
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