any 5v 1amp source.
lots of those "USB packs" seem to work. wouldn't be difficult.
I have just done some measurements. MR-1 is said to draw ~1/2 ampere at 5 volts = 2.5 (running) watts, measured ~.25 amps charge when off, NOT running.
Connected to charger draw turned on running goes to .45 amps so charging/running
together seems the maximum; near KORG's spec power.
Charger
drops out to then run on the internal battery at ~4.6 volts external applied charger voltage, but ICON on LCD shows
still charging until external voltage drops down to 4.1 volt. At 4.1 input volts the BATT ICON shows the battery bars.
This means MR-1 hard connected to 4 NiMH cells will NOT work well to fully use NiMH cell's full capacity (to ~4.2 volts) before deck disconnects charging/running 4.6 volts and depending make/condition of NiMH cell, leaving as much as 50% external cell capacity
untapped.
Now I'm waiting for the battery to fully charge so
just deck running power is measured to know external battery power budget for just running the deck.
BATTERY SIZING 101:
If looking for a battery pack for running
so many hours, and know the external pack internal battery size, do the math with battery
voltage x ampere capacity = ~
watt capacity of the external pack maximum.
Sometimes the selling retailer does not list the pack's internal battery voltage and ampere capacity, but try to find this going to the pack maker's web page technical description for best chance of finding this. Most of these external rechargeable packs use just ONE 3.7 volt lithium battery at some ampere capacity.
Actual available watts at 5 volts pack output will be (10%-25%)
less than that, but you'll know at least
ideal run time by dividing external pack watts by 2.5 deck watts. So be conservative in estimated running time from any pack until fully 'rundown' tested.
TIP: New packs need 2-3 use to ~60% remaining, recharges to fully wake up to maximum capacity, and then will last up to 2 years before losing 20%
or more capacity/runtime ability.
So SUGGEST best to BUY NEW having
50% MORE capacity
than expected to actually need.
PERSONAL EXAMPLE: My own BC-MT4 for Microtrack deck with USB output plug can be instead fitted with 4 x 1.7 mm locking barrel connector required by MR-1 power jack
. I planned to do this if there's time. This external pack has ~40 watt capacity using 4 C alkaline cells that when divided by 2.5 watts needed by MR-1 = ~16 hours 'ideal' runtime. This pack 'recharges' in seconds anywhere with fresh cells inserted.
16 hours runtime is far more than most recordists need for doing an evening concert or session, and then returning home, but exactly what's very needed for those doing days of recording in remote locations where recharging external packs is not so practical, or simply wanting recording runtime reliability as moot issue.
AND, however convenient, reliable, and powerful, disposable flashlight cell type packs seem
not environmentally kind!
This is less an issue with packs using much larger capacity D cells having 35-50 Hr recording time, and needing 'refreshing'
every year or two(!) if used every month for recording one or two events.
What's interesting is most lithium rechargeable pack batteries fully work same 1-2 Yr. length of time, and have lost enough reliability/capacity for owners
to be disposed for cheaply getting another! So in some situations, about the same burden on the environment using either battery type, or so I am thinking.
