In case anyone else runs into this problem with the Fostex FR-2LE,
here is what I've observed since my original post: this high-frequency
artifact occurs consistently when using the supplied AC power supply,
when phantom power is turned on. It has not occurred when using fresh
batteries. I have once encountered a similar, lower-level pulsed tone
at the end of a long recording when using alkali batteries that were
running down.
--- In Carter Scholz
<> wrote:
>
> Hi,
>
> I recently bought a Fostex FR-2LE and I've been making some test
> recordings with it. I've noticed a steady tone that shows up only
> when phantom power is turned on. When sampling at 96/24, the tone is =
> on both channels at about 30,700 Hz; with trim and gain up full,
> using AT 3032s, it is about -66 dB (L channel) and -72dB (R
> channel). If the internal mics are used, with phantom on, the tone
> is there, but at a lower level. When sampling at 44/16, the tone is
> somewhere around 16 kHz, about the same levels. If phantom is turned =
> off, and internal mics used, there is no such noise at any sample rate.
>
> I assume this is electrical noise from the switching circuit used to
> generate the P48. Has anyone else observed it? Is this typical of
> the Fostex, or do I have a bad unit? And why would it change
> frequency depending on the sample rate?
>
> It's a small amount of noise, but if you shift the 96/24 file down
> three octaves, it is definitely audible.
>
> Carter Scholz
>
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