I first decided to try 4 NiMH AA batteries to power a HiMD recorder,
because I measured the output from the supplied 120VAC to 3VDC adapter
and found it supplies 5V.
Since the HiMD manual states 3V, I am hesitant to use anything much
above the 5V that the adapter provides. Each time I have used my 4xAA
battery pack, I have measure its output before hooking up to the
recorder. The first times I tried it I used batteries that supplied
about 4.8V, but have gradually tried higher voltages up to 5.6V (newly
charged NiMH) with no noticeable problems.
For peace of mind, adding a voltage regulator would seem to make
sense. I plan to try the LM317 that Rich Peet mentioned. Another
option might be using the 5V USB battery holder that Oryoki recently
pointed out -
http://www.batteryspace.com/index.asp?PageAction=3DVIEWPROD&ProdID=3D2970
- then adapting it for a type-A plug.
John Hartog
--- In "Adam Liberman" <> wrote:
>
> Hi,
>
> --- In "Rich Peet" <richpeet@> wrote:
> > DC-DC converter in the normal primitive sense is a Voltage Regulation
> > IC. A common one is the LC7805 which is a 5 volt regulator.
> ...
> > In recent years some manufacturers are getting smart and using this as
> > an advertising plus. The SD722 recorder markets their recorder as
> > being able to accept 10 to 18 volts. They likely are using a LC7805
> > and allowed a 2X safty for voltage spikes and the like.
>
> This is incorrect. A xx7805 is a IC linear regulator. A DC-DC
> converter is completely different -- it is a switching regulator, and
> contains various ICs and transistors as well as capacitors and
> inductors. Sometimes all this is contained within a sealed module. A
> linear regulator works by dropping the excess voltage as heat, so it
> is wasted. A switching regulator turns on and off very rapidly
> (usually 40KHz and up) to regulate the voltage, so it can be very
> efficient (up to 93% or so), and wastes very little power as heat. The
> trick in designing audio devices is to prevent any of the switching
> noise from becoming audible.
>
> Virtually all portable battery operated devices use switching
> regulators in order to conserve battery life and reduce heat, and do
> not use linear regulators like the 7805. When the SD722 says 10 - 18
> volts, that is an absolute range. The switcher likely can not reduce
> its duty cycle any further to regulate a higher voltage. In addition,
> a higher voltage may exceed the maximum voltage and power ratings of
> the semiconductors, inductors, and capacitors in the circuit and
> damage the recorder. Some devices, like some cassette and minidisc
> recorders, also use the unregulated battery voltage to power some
> circuits, and exceeding the specified voltage range may destroy these
> components.
>
> On portable recorders that only specify one input voltage, like 6
> Volts, it is likely they can tolerate a little more, like 6.4 (fresh
> batteries) or 7.5 (unloaded unregulated power adapter). But without
> analyzing the schematic for voltage and power ratings, and testing the
> internal heat dissipation at various voltage levels and ambient
> temperatures (which no-one is likely to go to the trouble to do), or
> having input voltage specifications from the manufacturer, you should
> keep the input voltage very close to the specified figure.
>
> Thanks,
> Adam
>
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