FR2 and white noise.

[Mikkel Nielsen]

Hi all

Im having a bit of a problem with my Fostex FR2 and 2 connected mics.

Here is the deal:

I connect my figure-8 (+48 volt) mic together with my 416 to my FR2 Left and Right input, and I get a low volume white noise. Take out the figure-8 mic and all is good. Putting another +48 volts mic in, all is is good. Bringing back the figure-8, white noise again.

So I figured it might be the mic, and just for fun tried to connect the 416 and the figure-8 to my DAW. Everything is fine
Could this be because my FR2 cant deliver enough phantom power?
Or maybe some software bug in the FR2?

Your help is greatly appreciated! Thanks alot.

Best wishes,

Mikkel

[John Willett]

What is the fig-8?

The 48V phantom spec. actually states 10mA - but many equipment can't supply it.

The Sennheiser MKH 30 draws 2mA, The Neumann specs 4mA and the Schoeps is similar to the Neumann at 4mA (but rises to 8 or 11mA on 12V phantom).

Or could it just be the fig-8 picking up air movements - the diaphragm is fully open both sides and is more prone to these things.

[Mikkel Nielsen]

Hi John
Thanks alot for replying.
The fig-8 is the Emesser from Ambient Recording.

Here are the specs:
polar pattern bidirectional / "figure of eight"
frequency response +/- 3 dB 200 – 16.000 Hz
sensitivty 12 mV/Pa
signal to noise ratio CCIR 66 dB
signal to noise ratio DIN/IEC 79 dB - A
equivalent SPL rated at CCIR 28 dB
equivalent SPL rated at DIN/IEC 15 dB - A
max. SPL 132 dB SPL
dimensions l x d 53 mm x Ø 20 mm
weight 40 grs.
powering 48 V phantom power
mating connector TA3F
wiring pin 1 = ground
pin 2 = audio (+)
pin 3 = audio (-)


Dont think the Emesser is picking up the air. It doesnt happen when Im recording onto my DAW. The FR2 and DAW recordings are recorded the same place.


Best wishes,

Mikkel

[John Willett]

I don't know your mic. personally - is it a single diaphragm? or back-to-back cardioids?

It's sensitivity is not that high, so it's unlikely to be air noise.

It could be it draws a lot of current (you don't say in the specs you quoted) and the FR-2 can't provide it.

I never had this problem with my own FR-2 (not got it now, though - I sold it when I bought the Nagra VI), but I only ever used mine with Sennheiser MKH mics which only draw 2mA.

I would look up your mic. on Google, but I have to rush off to Pinewood Studios and don't have the time at the mo.

[Mikkel Nielsen]

Thanks John.
Here is the homepage:
Ambient Products Emesser

I have emailed the company too. Hopefully they will know what to do.

Best wishes,

Mikkel

[ghellquist]

What you can do meanwhile is to use a multimeter and measure the Voltage. ( Unless you have one, you should be able to find one for less than 20 Euro ).

First measure without any mics. Between pin 1 and either 2 or 3. This should read roughly 48 V (the phantom specs says 44 to 52 Volts).

Secondly connect your figure 8 mic and measure on the other mic channel. A good phantom power supply will not sag very much, a less well-done might show a much lower voltage.

Maybe your figure 8 mic is faulty and drawing a lot of current, and this in combination with a less than perfect power supply might be the culprit. Or again, something completely different might be the reason.

// Gunnar

[Mikkel Nielsen]

Thanks Gunnar.
I´ll try that.

Best wishes,

Mikkel

[Mikkel Nielsen]

Didnt have time to measure the FR2 with a multimeter, but I have tried the mics on a Sony PCM d50 recorder, and everything works fine.
Must be something wrong with the FR2.
Guess I have to be buying, either a portable phantom power unit now, or a new recorder.

Thanks to all.

Mikkel

[Mikkel Nielsen]

Have measured the volts on the FR2. Everything is fine. +48.8 on every pin I measure.
I have tried to connect a Røde NT4 stereo mic to the FR2, and the same noise actually appears when I turn on the FR2´s phantom.
When I also turn on the internal battery in the NT4 (together with the FR2´s phantom)...The noise is no more present
Seems like the problem comes whenever I use the 5-pin stereo XLR, to stereo 3-pin XLR(s) cable.
Really frustrating!
This cable is also used when everything is connected to the Sony PCM D50, with no problem what so ever.


Mikkel

[John Willett]

Originally Posted by Pindebraende

Seems like the problem comes whenever I use the 5-pin stereo XLR, to stereo 3-pin XLR(s) cable.

Sounds like it could be the cable, then.

Check how it's wired.

5-pin should be:-
pin 1 = screen
pin 2 = Left +ve
pin 3 = Left -ve
pin 4 = Right +ve
pin 5 = Right -ve.

[Mikkel Nielsen]

Thanks again John.
Yes I thought so too, but the cable and mics works perfectly on the Sony recorder No noise here.

Mikkel