• Registered: 2014-10-23
  • Posts: 10

Topic: Quadmic II SIG less while on phantom power

I was doing some tests the other day involving my Quadmic II and noticed something unusual (at least, I think it is unusual).

The testing involved running a Rode NT4 through the quadmic going line into a Tascam DR-680, alternatively using phantom power and the NT4's onboard battery.

I first powered the NT4 with the battery (so quadmic wasn't providing phantom power) and set the levels on the quadmic based on the level display of the DR-680. The green SIG light on the quadmic turned on as expected when the NT4 is given a signal.

Then I removed the NT4's battery and switched on the Quadmic's phantom power. Adjusted levels on the quadmic so things would show the same on the DR-680's display. The resulting files did indeed give the same level. However, the quadmic's SIG light didn't turn on until it was provided much more level, enough level through the NT4 to come very close to overload (red light).

I noticed something similar before with different (non stereo) mics, that can't be powered from a battery. I didn't think anything of it at the time, but should retry those mics with an outboard phantom power source.

In other words, the behavior of my quadmic's SIG indicator appears to be somehow connected (and adversely related) to the presence of phantom power on the quadmic.

The workaround is to go by the signal level indicator on whatever device the audio is going to from the quadmic. But is this a known problem?

Regards, Christine

2 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,599

Re: Quadmic II SIG less while on phantom power

I can not explain this behavior. In the circuit design it is impossible that phantom power on/off changes the SIG LED. But you could do some simple tests to further evaluate it. First switch off/on the Low cut and Phase to see if one of both changes the effect. Second please measure the point where the SIG LED turns on with and without phantom power by reading the meters in your DAW (best level meters of TotalMix FX or DIGICheck).

Regards
Matthias Carstens
RME

MC's Website

3 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
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Re: Quadmic II SIG less while on phantom power

I just rechecked - as expected my QuadMic II does not show any difference on the SIG LED with phantom on or off.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2014-10-23
  • Posts: 10

Re: Quadmic II SIG less while on phantom power

I will do some more testing this evening and will let you know what the results are.

Regards, Christine

  • Registered: 2014-10-23
  • Posts: 10

Re: Quadmic II SIG less while on phantom power

Well, I can't reproduce the problem using a somewhat different setup.

What I did now was take a Shure KSM141, with an external phantom power supply, into the Quadmic II and then line into the DR680. Set the Quadmic's gain to 30dB.

The SIG light on the Quadmic lights up right where the dotted line is on the DR680's level indicator. Perfect.

Then I took the external phantom unit out and used the Quadmic II's phantom power. The SIG light came on exactly the same as before.

I did the same thing with a Rode NT5, same result: works just fine.

So "problem" solved: there never was a problem to start with.

Perhaps previously with the Rode NT4 being a stereo mic the power requirements a bit different and providing phantom power to only one of the two cables causes things to be a bit different.

Either way, thank you for your patience... 

Regards, Christine