[zilch0md]

Quote:

Well that puts it within range of the Energizer power packs without needing any fiddly adapters.

 
Yes, but my brand new fully charged Energizer XP8000 or XP18000 could output 20.2 Volts (for loads up to 3 Amps) from its blue jack - which exceeds the Hi-Fi-M8 (and DACmini CX) maximum input voltage of 20.0 Volts (per Michael Goodman, above) by 1%.  
 
This might be OK, but there's a safer alternative - use the green jack instead.
 
 

Now that my XP8000 is 18 months old, following many charge cycles, the blue jack is putting out 19.50 Volts, when fully charged - still more than the 19.30 Volts (measured) that the DACmini CX AC power supply (and that of the Hi-Fi-M8 ?) can produce - but well below Michael's specified maximum of 20V.
 
In my opinion, one should use the green (12-Volt) jack when powering a HiFi-M8 or DACmini CX from the Energizer XP8000 or XP18000, especially when the power pack is brand new.  It will sound just as good with 12.6 Volts instead of 20.2 Volts, because, as Michael wrote, above:
 
 

... we re-manufacture all power inside, so we don't care what you feed the unit, as long as the power supply can feed several amps of current [and it's within the range 9 to 20 Volts].

 
When choosing an external battery pack, you have to make sure it supplies enough current (Amps) in addition to a DC voltage that fist the range Michael has specified.
 
The Anker Astro3 10,000 mAh LiPo battery pack, for example, which I've used with the Meier Stepdance and the iBasso PB2, gives you a choice of 5V (via a USB jack) and switchable 9V or 12V output via a barrel connector, but it's maximum current output is only 2.0 Amps vs. the XP8000 and XP18000's 3.0 Amps. 
 
Going by Michael's spec for the HiFi-M8's switch-mode power supply, both the Hi-Fi-M8 and the DACmini CX power supplies provide 19V at 2.6 Amps.  (My DACmini CX power supply is labeled 19V 2630mA.)  Thus, at only 2.0 Amps, the Anker Astro 3 might not supply enough current for either the DACmini CX or the Hi-Fi-M8.
 
Here's a great article, dated 9 March 2011, from Tom's Hardware, reviewing several external battery packs.  Don't miss the charts that show how they rated in terms of capacity (play time) per pound as well as other measurements.  (Unfortunately, Tom's Hardware failed to test/confirm any of the rated output voltages.)
 
Mike

 

[NorthernAvengeR]

So is the rectangular usb port for idevices only and the square one for computers/android etc? Just asking if I need a new cable if I want to use the m8 with my Gnote2. Not sure Ive seen any micro to to regular usb-a otg cables before.

 

[mgoodman]

Quote:

So is the rectangular usb port for idevices only and the square one for computers/android etc? Just asking if I need a new cable if I want to use the m8 with my Gnote2. Not sure Ive seen any micro to to regular usb-a otg cables before.

Yes, rectangular one is for iDevices (M8 takes usb audio from them, charges them). Square one is for laptops, desktops and [compatible] androids. In order to feed an andorid into M8 you'd need a cable that terminates on the M8 side with a large square USB plug.

 

[mgoodman]

Quote:

 
Yes, but my brand new fully charged Energizer XP8000 or XP18000 could output 20.2 Volts (for loads up to 3 Amps) from its blue jack - which exceeds the Hi-Fi-M8 (and DACmini CX) maximum input voltage of 20.0 Volts (per Michael Goodman, above) by 1%.  
...
 

...

I believe you will be safe with either the blue or the green jack. We publish 20V as the top limit, but the circuit can take up to 23V, so you should be ok. Thanks for a nice picture with explanations.

 

[Audiowood]

Thanks Zilch0md. I actually follow your step dance thread with the research of the battery enhancement and have enjoy every minute of it. I actually bought everything you have recommended and it brought up the sq. Had never thank you enough, so thank you again.

 

[NorthernAvengeR]

Okay. That complicates things slightly. I don't think anyone makes an elegant micro-USB to USB Type-B OTG cable solution.

 

[FraGGleR]

Quote:

Okay. That complicates things slightly. I don't think anyone makes an elegant micro-USB to USB Type-B OTG cable solution.

 
If you jumper pins 4 and 5 on a standard micro-USB B connector, it should trigger the USB Host mode of your phone.  Then it is as simple as hooking up the rest of the wires to a USB B connector.  I'd be surprised if you couldn't find something on eBay that could do the trick.  If not, PM me.  I have made many different permutations of short USB cables, including the obscure mini-A to 30-pin used on the new CLAS dB.  Very happy CEntrance is using standard USB plugs instead of outdated mini A/B connectors.

 

[Akula1321]

Do you know if these phones work with an external DAC? If so, they should work with the Hifi-M8. Give me a model number and I will research further.

Yes they do, I use one as well as many others. There are DACs, DAC/Amps that take digital USB from Nokias, Samsungs and iPads w/ camera connection kits. I think the USB receiver chip has to be capable as well. PM'd.

 

[zilch0md]

Quote:

I believe you will be safe with either the blue or the green jack. We publish 20V as the top limit, but the circuit can take up to 23V, so you should be ok. Thanks for a nice picture with explanations.

 
Excellent, thank you!   I'll start using the XP8000's "16-20V" blue jack with the DACmini CX (when I want to be off the grid).
 
Quote:

Thanks Zilch0md. I actually follow your step dance thread with the research of the battery enhancement and have enjoy every minute of it. I actually bought everything you have recommended and it brought up the sq. Had never thank you enough, so thank you again.

 
You're very welcome!  
 
Many portable amps lack the power management sophistication of the HiFi-M8, but can be "tweaked" by increasing the supply voltage to the maximum allowed by the amp's designer.  In my limited experience, both the Meier Stepdance and the iBasso PB2 enjoy greater dynamics and bass authority when using a max'd out external battery rather than their respective internal batteries.
 
Personally, I am amazed that CEntrance has given the HiFi-M8 the same "any-voltage-between-9V-and-20V-is-fine" power management technology that the DACmini CX incorporates - maximizing sound quality independent of supply voltage.  I've tested this thoroughly with the DACmini CX - it sounds just as good with a 9V power supply as it does with 19V power supply - even with relatively inefficient headphones like the Beyerdynamics T1.
 
Try reducing the supply voltage with just about any other brand of portable amp that has an internal battery pack.  As the voltage of an internal battery pack decays with use, the sound quality will also decay because the amp's output power (Watts rms) will decrease as the input voltage to the op-amps decreases.  Not so with the HiFi-M8.  I don't even have to listen to a HiFi-M8 to know that what I'm saying here, is true.  As soon as I read Michael's comment that the HiFi M8 can use any voltage between 9V and 20V, I recognized the REAL value of this is that the HiFi-M8 will deliver a CONSTANT, best-possible sound quality, throughout the battery's discharge cycle, during portable operation!
 
I would guess that the vast majority of portable amp users have no awareness of the impact that supply voltage can have on sound quality. Given that nobody is out there demanding this technology, this is a gift from CEntrance to the community -allowing the HiFi-M8  to deliver the best possible sound, all the time - even as the voltage of the internal LiPo pack decays with use, until it's time to recharge it again!   I personally don't know of any other portable amp that does this. 
 
It just makes me wonder what else is happening under the covers of this spectacular piece of portable Head-Fi gear!  
 

 
Mike

 

[Armaegis]

Quote:

Personally, I am amazed that CEntrance has given the HiFi-M8 the same "any-voltage-between-9V-and-20V-is-fine" power management technology that the DACmini CX incorporates - maximizing sound quality independent of supply voltage.  I've tested this thoroughly with the DACmini CX - it sounds just as good with a 9V power supply as it does with 19V power supply - even with relatively inefficient headphones like the Beyerdynamics T1.
 

 
Is there a difference in life on your battery pack when feeding the DACmini CX the 9V vs the 19V ?

 

[zilch0md]

Quote:

Is there a difference in life on your battery pack when feeding the DACmini CX the 9V vs the 19V ?

 
I've never tested XP8000 playback times at different voltages. I suppose I'm not patient enough to keep track of that.  

 
I have a theory though, that warrants testing:  I suspect that the XP8000 and XP18000 each have five cells producing a maximum of 4.2V, three of which are tapped in series to produce 12.6V at the green jack, with all five of the cells tapped in series to produce a maximum of 21.0V at the blue jack.  Again, I'm only guessing.
 
If this is true, that you're only using 3 of 5 cells when plugged into the green jack vs. 5 of 5 cells when plugged into the blue jack, you would get more minutes of playtime when using all five cells, instead of just three, assuming the HiFi-M8 (or DACmini CX) pulls the same total number of Watts whether you supply it with 12.6V vs. 21.0V.  
 
So, just guessing, I'd say you'd likely enjoy a greater run time using the highest voltage offered by the XP8000 (all five cells, instead of only three) - but I'm only conjecturing.  At least we now know that the HiFi-M8 can handle up to 23V, so there's no problem with using the blue (16-20V) jack, in any case.
 
Mike

 

[Armaegis]

I kinda doubt that's how it would be, since that would lead to premature wear of some cells over the others.

 

[zilch0md]

I hear you.  

 

[Armaegis]

If the M8 does it's own voltage regulation, then I think using the minimum voltage required would offer the greatest life out of a battery pack. Otherwise all that excess voltage gets shunted off as heat or whatever else it does. Well, maybe/maybe not. I'm not fully educated on what exactly goes on in a voltage regulator. A resistor divider would waste all the energy as heat, but I imagine a proper regulator is significantly more sophisticated than that.

 

[mgoodman]

Quote:

Personally, I am amazed that CEntrance has given the HiFi-M8 the same "any-voltage-between-9V-and-20V-is-fine" power management technology that the DACmini CX incorporates - maximizing sound quality independent of supply voltage.

Thanks, Mike. There is only one draw-back to this approach. The audio will be fine all they way up until it just drops out. There will be no "gradual worsening". The circuit will hold the voltage until it decides that it's a "lost cause" due to significant battery discharge. Then, it's just off, like a cell phone. There will be LED indication for battery voltage on the side, so you will know whether you are at 15%, 50% or 100% of battery.