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Re: Fostex FR-2LE ?

Subject: Re: Fostex FR-2LE ?
From: "Gregory O'Drobinak" gmo_dunes=
2
Date: Wed May 14, 2014 12:33 am ((PDT))

Greetings!

I have used my DR-680 for several years and have had my share of practical =
issues with remote powering via batteries.

In order to have the least amount of grief, I would strongly suggest using =
batteries that do NOT go below around 11.0 volts when drained (end of cycle=
 before recharge).
This is in agreement with Tascam's spec of not going below 12 volts or abov=
e 15 volts.
I have verified this, along with several of my colleagues, to be true.=C2=
=A0

When recording using 12 volt AGM batteries (gel cells) to power the unit, t=
he DR-680 mic preamps start to degrade at some point below 11 volts, with m=
otor-boating occurring first, then no audio for some time before the track =
audio stops due to extreme voltage drop. The solution is to use 12 volt (AG=
M) batteries with at least an 18 AH (Ampere Hour) rating (mine are 22 AH) f=
or an overnight 'drop' of around 12 hours maximum.=C2=A0
In order to not have the battery go below the safe discharge voltage level =
for the DR-680, I would size the battery to have 1.5 AH per hour of recordi=
ng.
So 12 hours would require a 12 x 1.5 =3D 18 AH 12 volt battery. This is wor=
st-case with all six mic preamps running with phantom power.

I have measured the current draw of the DR-680 to be 0.8 amps with all=C2=
=A0six mic preamps running with phantom power.=C2=A0
But you have to take into consideration that the battery powering the DR-68=
0 cannot go below around 11 volts.
Then you need to take into account the discharge rate curves for the batter=
y that you use so that the output voltage stays above the ~11 volt cutoff p=
oint for the entire period of your recording session.=C2=A0
That is why you need to size the battery at around twice the actual current=
 draw rate.
And it doesn't much matter what kind of battery technology one uses, as the=
 voltage starts to fall more than about a volt below 12 volts, the mic prea=
mps start to degrade, then quit.

One other observation is that the DR-680's internal circuitry is not smart =
enough to switch over to the internal batteries as the external battery vol=
tage slowly drops.
If you have an external battery that is still above ~ 11.5 volts and you pu=
ll out the plug to the unit, it does seem to switch over properly.=C2=A0
But not when the external voltage drops slowly, as in the case of an extern=
al battery that follows a slowly-falling discharge curve.

Given these observations, I can't believe that those Sony 7.2 volt camcorde=
r batteries would work properly with the DR-680 for any period of time.=C2=
=A0
The fellow from Raven must be running the internal circuitry of the DR-680 =
so low that the internal regulator is not even operating as designed, which=
 is quite sub-optimal and not to be done if you want the unit to last for v=
ery long.=C2=A0
I wouldn't do it, myself, under any circumstances.=C2=A0

It is true that the Sound Devices recorders can use such camcorder batterie=
s, but it is important to note that where that battery connects internally =
to power the recorder is different from the path from the 10 - 18 volt exte=
rnal power jack.=C2=A0
This is NOT true for the DR-680.
So my advice is to not use those camcorder batteries on the DR-680.

If you do some searching of this group's archives, you will find some posts=
 by David Michael regarding some specific (lithium-ion ?) light weight batt=
eries that gave him some good record time with the DR-680.
But these were 12 volt packs, not 7,2 volt camcorder batteries.


Good luck & happy recording!

- Greg


From: "H=C3=A5kan Olsson  [naturerecordists]" <natur=
>
To: "" <>
Sent: Tuesday, May 13, 2014 3:55 AM
Subject: [Nature Recordists] Re: Fostex FR-2LE ?



=C2=A0
Hi John.
Yes they have a minimum of 12v in the specification for the DR-680. Actuall=
y I don't think there is something wrong with experimenting but if you go o=
utside the specs you shouldn't blame the manufacturer...
It seems that using 9v DVD batteries is very common on this and other units=
.
I watched this (http://www.blackravenfilms.com/#!Tascam-DR-680-Field-Record=
er-Review-and-How-I-Power-It/chsu/633EF75D-44F0-4EE1-A20A-DE54BAA54049) vid=
eo and he recommends Sony DVD batteries. I don't know but I think they are =
9v batteries.



--
/*
H=C3=A5kan Olsson
*/





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