there is a slew of problems with phantom power in these low voltage digital
devices.
i first came up with it with a digidesign mbox, intermittent whine on one or
the other channels which went away when phantom was switched off. not so
serious, but occassionally audible whine on a presonus inspire (a firewire
device). i heard some awful noises on the zoom which i think came from the
phantom power. i heard the noises on the m-audio 24/96 as well.
i think the culprit in all these is the switched mode phantom power and
probably the best thing would be an outboarded phantom power. it does not
always have to be 48 volts - depends on the mike of course, but i have run
oktava mko12 (a simple resistor for the condensor DC voltge) on 18 volts with
only a small loss in sensitivity.
umashankar
----- Original Message ----
From: Klas Strandberg <>
To:
Sent: Wednesday, March 21, 2007 5:02:15 PM
Subject: [Nature Recordists] Phantom power noise - again!!!
Lindsay Cargil reported here on the list a while ago, that he had
problems using his Telinga PRO6 handle with the Fostex FR2. In the
end, the Fostex repair shop in UK replaced a PC-board and the problem
was solved. No more noise.
Lindsay had the same noise problems when running his Sennheiser EM62.
I got my FR2 on a sale here in Sweden, and found that the phantom
power caused noise with the PRO6, similar to the noise which Lindsay
reported. The only difference was that his noise appeared after a few
seconds, while my noise appeared instantly.
The tested PRO6 handle worked fine into the FR2 when the phantom
power was off and the PRO6 running on battery.
Then the similar problem / noise was detected when testing another
FR2 machine with PRO6. Again, the noise disappeared when the handle
was run on battery.
The noise is gentle and low-frequent and sounds very much like
distant traffic noise. One can easily think it is normal background noise!!!!
Lindsay first though that it was the PRO6 base filter turning on and
off, by random!
Both PRO6 handles which I have tested, worked fine into my bench amp,
into SD702, into the Zoom H4 and into Tascam DA-P1.
One of the tested FR2 was also tested with MHK20. No problem.
I have now got in touch with Sennheiser, Sweden, which sold my
machine. I want it repaired as Lindsay got his repaired, or send it back.
Phantom power is created by chopping direct current from the battery
into pieces and stepping it up to a higher voltage, 48v. If the
chopping process is not frequency stable, all kinds of problems may
occur, often different from machine to machine, and dependant on
temperature and other conditions. Also type of batteries used.
Either it is stable, or it is not, and this depends on the technical
design used.
As I said, one of the FR2 worked fine with MKH20. But that doesn't
mean that it is going to work as fine when the temperature is
changed. I also made a mistake when testing it - I only tested it
with one MKH20 connected. It may very well start making noise if I
had connected two MKH.
So, there might be a little warning sign about the new Fostex. Are
they using the same principal design as in the FR2, or a stable one??
The PRO6 handle can run both on phantom power and battery. That way,
it is simple to detect even a low phantom power noise. You just have
to make two recordings and compare - one with phantom power and one
on battery.
But how does the user of a ME62, for example, detect an error, when
the error sounds like normal background noise??
Lindsay detected his error, as it appeared after a few seconds. But
in my case it is there from the start. I'm not sure that I had
detected it, if it hadn't been for Lindsay.
Micro-Track 24/96 is the other machine with the same problem, but
here it is easily detected, as the noise is high-frequent and "scratchy".
I am going to make a power box for PRO6, with balanced outputs, which
can be sent around between PRO6 users around the world. It would be
very interesting to find out the difference between battery power and
phantom power on the Marantz PMD-series, for eample.
If you are running a PMD of some kind, or some other model with
phantom power (NOT Sound Devices, MT 24/96 or FR2) - please get in
touch with Telinga.
As everyone can understand, I don't want anybody to blame the PRI6
handle, when the cause is in the recorder.
Klas.
. I had the same At 09:56 2007-03-21, you wrote:
>looks good, but no specs on the mic pre-amps?
>if the mic pre's are good it could be a great machine,
>doesn't look too big either.
>i might just hang fire on buying an MZ-RH1 as this
>costs only a little bit more, but it all hangs on
>those mic pre's.
>
>Phil
>
>--- david briggs <> wrote:
>
> > new info on fostex page:
> >
>http://www.fostexinternational.com/docs/pro_products/fr2le.shtml
> > prices upon studio spares site and HHB...also Us
> > sites zzsounds etc.
> >
> > dave
> >
> > [Non-text portions of this message have been
> > removed]
> >
> >
>
>
>
>
>
>
>___________________________________________________________
>New Yahoo! Mail is the ultimate force in competitive emailing. Find
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>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
Telinga Microphones, Botarbo,
S-748 96 Tobo, Sweden.
Phone & fax int + 295 310 01
email:
website: www.telinga.com
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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A listening room is not nature."
Klas Strandberg
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