At 03:59 PM 2009-08-03, Marinos Koutsomichalis wrote:
>I just noticed sth strange with my pmd661
>
>I wanted to test if the noise I got on a recording was due to the
>mics I used or the pre-amps of the machine, so
>I just plugged the headphones and without anything connected I pumped
>up the gain.
>I noticed that I got 2 times more noise when phantom power was on !
>
>I was wandering if this is normal.. or it might be a problem with my
>machine only ??
Normally, testing an input open circuited is pretty much meaningless.
The inputs are fed from a specific (low) source impedance that helps
determine the noise.
The ideal way to test is to terminate the input in the anticipated
microphone source impedance (200 ohms is a good choice for a balanced
microphone, although many specs also use 150 ohms as the source impedance).
Do not rely on any tests you make open circuit.
If this unit has XLR inputs, then connect the resistors between pins
2 and 3. Metal film resistors of 1/4 watt or greater would be fine
(you'd need higher wattage resistors if you were connecting either
pin 2 or pin 3 to ground, but since you're not, then 1/4 W would be fine.
Cheers,
Richard
Richard L. Hess
Aurora, Ontario, Canada http://www.richardhess.com/
Detailed contact information: http://www.richardhess.com/tape/contact.htm =
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