I received the boost converters today and can confirm they work perfectly. I have tested them with input voltages between 1.5v and 5.0v and the output voltage remains stable at 5.0v. [..snip..]
Any suggestions?
Try powering them using PIP from the recorder, and from a few different recorders if you have them available, confirming good output voltage. I'd then modify a standard battery box circuit, replacing the battery with one of the converters. Should be able to use a single converter in place of the battery.
1) +V in to the converter taps into Signal+ on the recorder side of the series DC blocking capacitor in the battery box circuit. Do so through a series resistor, same value as the others in the circuit.
2) +V out from converter gets connected the same as the battery it is replacing (through the resistor on the microphone side of the blocking capacitor).
^ Duplicated for both channels, you'll end up with 4 resistors total, in pairs arranged symmetrically on either side of the capacitors.
3) Try it.
4) Maybe add capacitance in parallel to the V+ out from the converter to achieve a cleaner supply to the mics if needed. Not sure if such supply filtering will be needed or not or what the appropriate value might be, but won't hurt to include it. Intent is to filter out any high frequency switching noise from the converter. The converter's stated operating frequency is 150kHz.
I'm not a circuit designer! Pretty sure the above should work, but fully open to correction from anyone who knows better!
If this works, it will eliminate the battery box battery and should work with any recorder that provides PIP. PIP current draw from the recorder will increase, so check battery run time while recording. Current draw for powering a pair of electret mics is pretty minimal, so hopefully the additional current draw due to the inefficiency mentioned below is a non issue. The converter along with the two additional resistors and possible filter capacitors should be smaller than a battery.. guessing maybe half the size of a 9V. Small enough that I'd look into building it into a small node placed at the Y junction of the mics>recorder cable.
No modification of the recorder is necessary as long as the recorder provides PIP on the desired input. But of course you can also could build it into the recorder if you like.
I took a look at the link posted for the converters. Here is the most helpful review-
"They are super-simple to use (just 3-wires), and they worked well out of the box. The 5V is stable and clean (add a few caps, downstream, of course).
They are not at all efficient. Best case, when the input voltage is 4.5V+ (fully charged battery), they yielded about 84% efficiency. However (and this dramatic a drop was surprising to me), the efficiency drops as the input voltage drops. With 2.8V going in (like when a battery is nearing exhaustion), the efficiency is 44%. Around 2.8V they get a little wonky and won't up-convert voltage much below that.
So this means that as your battery drains, the efficiency drops, requiring more and more power from the battery to satisfy a constant load, for example. It's an accelerating cycle that drains the battery really quickly.
That's too bad, since these are tiny, easy to deploy units with a relatively clean output. They're kind-of battery killers, though. Modern DC/DC converters should be able to maintain 90%+ efficiency over their full range of input voltages.
For non-battery powered applications where power does not matter, or your load is very, very light, and all you need to do is convert a voltage between about 3V-5V to a stable 5.0V output, they'd probably be OK."
Topic: CA-UGLY bit the dust, need another preamp solution for DPA 4061s (Read 25648 times)