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HeadAmp Pico Power: Pre-Order Thread - Page 21

post #301 of 730
Thread Starter 
Originally Posted by bcwang View Post

I have a couple of questions about the pico power that hopefully Justin can answer.


1.  Is the background hiss level for sensitive IEMs less than that of the Pico Slim?


It depends on the gain setting.  In low gain yes, in high gain no.


2.  At the lowest gain with sensitive IEMs listening at low levels, will you be listening above the volume pot's unbalanced portion?


Yes.  i hand test every volume pot that is used, and only take the ones that have good channel balance at low levels.


3.  Do the two 9v batteries have to be equivalent, what happens if one dies first.  I guess the real question is are the batteries connected in series?


Yes, they need to be the same.  The batteries are in series.  The amp will not function with a dead battery.


4.  Are there sound quality differences if you use different voltage 9v batteries, in the nimh variety they exist as 7.2v,8.4v, and 9.6v variants nominal voltage.


The higher the voltage battery, the more power you can get out of the amp.


5.  What is the max voltage the batteries can be?  The voltage can reach 11.52v each for a fully charged 9.6v nimh version.


i wouldn't go any higher than that


6.  Are there sound quality differences using batteries that can deliver more current (li-ion) vs those that can't (carbon-zinc)


if you are trying to drive a very inefficient headphone such as the hifiman he-6, the li-ion may be better.  they also maintain a more stable voltage thru their discharge.


7.  Does sound quality degrade as the batteries run down?


You would lose max output power


8.  Does it have a mechanism to let you know it's time to replace the batteries before just hearing distortion?


The power LED will turn off when the combined voltage is below ~12V



HeadAmp Audio Electronics - home of the Pico and Gilmore amps.  Now with Audeze, Fostex, HiFiMAN, Sennheiser, and STAX.
Find us at www.HeadAmp.com

post #302 of 730
Thanks for the answers Justin!

One clarification about one of the questions. So if the batteries are used in series meaning two of the terminals are just to connect the positive of one side of the battery to the negative of the other battery and nothing else? I've had problems with other dual 9v amps related to batteries not being exactly the same voltage.

Thought of three more questions:
1. Will the milliampere draw from the battery differ if source battery is a different voltage? Meaning if 2 sets of batteries are 200mah, one set being 7.2v and the other set being 9.6v, which one will last longer or it makes no difference.
2. What is the output impedance?
3. Can we order directly from the preorder page now without getting added to the spreadsheet?


Edit: updated with more questions
Edited by bcwang - 2/1/13 at 4:02pm
post #303 of 730

Just match your freeakin' batteries and let him finish the amps.....so close we can taste it.rolleyes.gif  If you are getting an amp close to $500. retail price how hard is it to match your batteries.cool.gif

post #304 of 730

^  biggrin.gif

Edited by cooperpwc - 2/1/13 at 3:35am
post #305 of 730
Originally Posted by dallan View Post

Just match your freeakin' batteries and let him finish the amps.....so close we can taste it.rolleyes.gif  If you are getting an amp close to $500. retail price how hard is it to match your batteries.cool.gif

I can tell you it is very hard to take care of 9v rechargeable batteries, especially of the nimh variety.  They have 6-8 cells (nimh) and having all of them all perform optimally among two sets of batteries, it's difficult since they are easy to damage by overcharge or over discharge due to not every cell being exactly the same but charged in series.  Then you won't have two similarly performing batteries with varying voltages throughout the discharge cycle and differing capacities.  There is no easy way to match two batteries, and my many 9v batteries are all in different states of performance over time. 


If the two 9v are truly used in series, then there is no fear of anything other than damaging the battery with over discharge.  But if they are not in series and require to be at nearly equivalent voltages otherwise potential dc current passing events could occur with the circuit, that would be dangerous for the headphone or the amp itself.  It sounded like Justin said they are in series but his other comment about the two batteries having to be equivalent gave me hesitation to really understanding what he actually meant by "in series".  If they are in series, I could mix a 7.2v and 9.6v battery in there and the amp would operate fine.  If they were the same mah capacity that would be no problem either as it would be the same as putting in two identical 8.4v batteries.


I do wish the circuit or power led cut off at something higher than 12v though, at a level that could protect the rechargeable batteries from reaching over-discharge.  However I do understand the difficulty of doing that as different chemistries (li-ion, nimh) and different available cell configurations make it difficult to choose one cut-off voltage for all cases.  Oh well, one just has to be careful with monitoring runtime and recharge before running the batteries too low.

post #306 of 730


post #307 of 730

can this drive HD800s?

post #308 of 730
Originally Posted by BoxBoxBox View Post

can this drive HD800s?

Based on the specs listed yes should output plenty of volume. This should also technically drive orthos like the HIfimans or audezes, plenty of output and gain. Keep in mind the output stage is discrete with current sources, Justin is not messing around with this one.
post #309 of 730

Paid, pre-order number 44 (orange)

post #310 of 730

Hey Justin,


Sorry if I missed these, but have you listed the amp's output impedance? What about the output  power into a 50 ohm load?



post #311 of 730


Are we getting close?   o2smile.gif

post #312 of 730

For me, this is such a tough call! I've never heard a Pico amp and would love to hear some impressions first, but that preorder price is mighty tempting. So far though, I've been really impressed with what two 9V batteries can do, whether in the RSA SR71a or the Neco Soundlab V3. Seems to be the sweet spot in powering headphones like the HD600/650... I also love when you can replace batteries yourself, as compared to sending something away to get a new battery. And Justin's 3 year warranty is really impressive too! 

post #313 of 730
About to pick up the li-po set from battery junction, but worried about the 8.4V nominal voltage. I might just go all alkaline.
post #314 of 730

I seem to recall someone selling a 4-set of Powerex 9V and charger on the forums not too long ago. 

post #315 of 730

I haven't even pre-ordered this and I'm recommending it! What are the odds that we'll hear more of how it sounds by Friday?! I read the InnerFidelity article but would have loved someone who had some more experience w/ portable amps to give a comparison. 


Edit: What the heck! I'm ordering one! 

Edit: Done and Paid! So much to love about the form, build and function. I hope it sounds as good as it's design! 


Cannot wait to know when they'll begin to ship! 

Edited by imackler - 2/5/13 at 2:44pm
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