Topic: CA-Ugly vs SP-SPSB-10

[one8ung]

CA-Ugly vs SP-SPSB-10


I soldered two DPA 4061 microphones to a 1/8-inch stereo jack.
The specifications says the microphones need Min. 5 V - max. 10 V

I measure 2x 4.35v on the 9v CA-Ugly box, now I thought I was smart and bought a 12v SP-SPSB-10 battery box and was hoping on 2x 6v but now I measure 2x 4.1v on it!

I measure with a standard electrical tester, has anyone measured with a true RMS meter?

[breakonthru]

10V is too high dont run those with a 12V bat box

"RMS" doesnt apply to dc voltage measurements

[one8ung]

The Ugly box is a parallel circuit in my understanding that's why both mics get 4.35 V

Or am I seeing that wrong too?

[audBall]

SP will modify the SPSB-10 to accept the smaller (mini) 9V batteries and did for mine. I haven't tested the output voltage or how long they last though.

[one8ung]

Installed a fresh battery but it gives me 4,1 volts again

[aaronji]

Maybe I am mistaken, but I think that you need to measure it under a load.

[jefflester]

Maybe I am mistaken, but I think that you need to measure it under a load.

Sure, but that would only make it go lower.

[DavidPuddy]

What are your batteries each measuring?

[one8ung]

It's a fresh battery...

[kuba e]

I think you should measure the same voltage on the battery box and the battery themselve. I'll try it when I get home. Maybe you have a damaged cable or a dirty connector. Try measuring the voltage directly on the battery box pins. In the first picture, is  the white wire ground?

[Sebastian]

Your Fluke tester is probably the problem here. The manual lists only a 2 kΩ input impedance for DC (see screenshot). This is a really low value. Almost all modern testing equipment has an input impedance in the 10 MΩ range, even the very cheap Chinese stuff.

I don't know the specifics of your battery boxes, but they will most likely connect the positive battery terminal to your mics through a resistor. This resistor forms a voltage divider together with your Fluke tester's input impedance. And since the input impedance is only 2 kΩ, the Fluke tester does not "see" the full voltage. My guess is that the internal resistor in your battery box is somewhere in the 2.2 kΩ range. Given a 9V battery, the voltage divider would result in a 9V * 2 kΩ / (2 kΩ + 2.2 kΩ) = 4.3 V measurement. That looks to correlate with your real-world measurement. Throw any cheap modern testing equipment at it with a 10 MΩ input impedance and that measurement becomes 9V * 10 MΩ / (10 MΩ + 2.2 kΩ) = 8.998... V (rounded to 9V).

The good news is that this also means your battery box is probably outputting the full 9V from the battery.

Just get rid of the old Fluke. It's no good, except for measuring a battery's open circuit voltage (and a few other things).

[kuba e]

I can confirm, I measured the same voltage on the battery itself and on the battery box. Looks like Sebastian has found where the problem is. Also Breakonthru is right. Be careful with the 12V battery, it can burn the dpa mics.

[one8ung]

Thanks for the explanation

I was thinking about the resistor or capacitors.

But of course it is also just a simple "tester" that I measure with.

[one8ung]

Just did a measurement with a voltcraft multimeter and 12 volts it is.

[one8ung]

SP will modify the SPSB-10 to accept the smaller (mini) 9V batteries and did for mine. I haven't tested the output voltage or how long they last though.

Working on it...