Originally Posted by zilch0md
This [dual 9V alkaline battery rig] is only a prototype that I wouldn't bother using in the field, as the battery capacity is too limited. I have not yet tested this cabling with two Anker Astro3 batteries (I have to buy a second one if I decide to go ahead with this):
This wouldn't exactly be "portable," but it could be considered "transportable" - for extended play in the absence of AC outlets.I suspect a single Anker Astro 3 could be used by employing blocking diodes to prevent the two circuits from seeing each other...
Thanks to Brunk's suggestion to research this with the folks at DIYaudio, we've determined that two 9V batteries are needed because (I've deduced this by taking resistance measurements of the AC adapter's connector plugs)... the HM-801 pulls 18V for one circuit (batteries in series) and 9V for another (batteries in parallel).
So, my friends, whatever you try to pull together in the way of an external power supply, you will need TWO independent 9VDC battery packs, as I had hoped to avoid.
But here's the good news: You can buy two (2) Anker Astro 3 for $110 and enjoy at least 5x the play time (20,000 mAh vs. 4,000 mAh) for only 1/3 the cost ($110 vs. $80 x 4). Four additional HiFiMan HM-801 batteries (totaling 20,000 mAH with the original) would cost $320 vs. $110 to achieve the same play time.
I still haven't tried this, and readers beware, you have to wire one 9V battery to the two connector tips and the other battery to the two connector barrels, checking polarities of both, as shown in my earlier posts. You also have to connect the two batteries serially, but I'm not going to document the schematic for that just yet because I haven't tested it. Proceed at you own risk - I'm just reporting what I know for sure.
Also: HiFIMan says they've never made a charging tray for the HM-801.
MikeEdited by zilch0md - 9/11/13 at 6:14am