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Thread: Digital noise on a sound recorder

  1. #21
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    No. It was digital noise from the Tascam coming back into the pre-amp down the wire which takes power from the pre-amp battery to the Tascam.
    I don't want to use the Tascam batteries because they run out too fast, but use the rechargeable battery in the pre-amp.
    Last edited by timtimtim; 1 Week Ago at 07:16.

  2. #22
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    Can anyone explain why the noise is virtually confined to one channel?

    Seems to have been power line borne so maybe a poor internal grounding regime?

    Dave.
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    Quote Originally Posted by timtimtim View Post
    No. It was digital noise from the Tascam coming back into the pre-amp down the wire which takes power from the pre-amp battery to the Tascam.
    I don't want to use the Tascam batteries because they run out too fast, but use the rechargeable battery in the pre-amp.
    OK, I am still a little confused. Are you saying you modified the power cord or you modified this inside the recorder its self? The battery provide power to the Tascam regardless if you use the pre amp feature or not. I often use a AT Pro 70 lav mic that supply's its own phantom power and I get around 12 to 14 hrs from the batts.

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    I only record on one channel - its film sound recorded with one mic.
    I use a very low-noise home-made pre-amp for the mic. I take power from the rechargeable battery in this pre-amp to drive the Tascam. Digital noise from the Tascam was coming down the power lead connecting the pre-amp to the Tascam, into the pre-amp where it was being picked up by the pre-amp circuit and sent as audio noise into the Tascam down the audio connector. I fixed this by adding three 3.3 ohm resistors in series with the power line to the Tascam, with three .1uF capacitors from the junctions of the resistors to ground, thus filtering out the digital noise. This has reduced the noise from quite loud down to almost imperceptible, barely noticeable above the mic hiss. Yesterday I thought it was perfect, but re-testing has shown it's not. This is disappointing. Now I'm wondering how to remove the last bit of noise?

  5. #25
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    Quote Originally Posted by timtimtim View Post
    I only record on one channel - its film sound recorded with one mic.
    I use a very low-noise home-made pre-amp for the mic. I take power from the rechargeable battery in this pre-amp to drive the Tascam. Digital noise from the Tascam was coming down the power lead connecting the pre-amp to the Tascam, into the pre-amp where it was being picked up by the pre-amp circuit and sent as audio noise into the Tascam down the audio connector. I fixed this by adding three 3.3 ohm resistors in series with the power line to the Tascam, with three .1uF capacitors from the junctions of the resistors to ground, thus filtering out the digital noise. This has reduced the noise from quite loud down to almost imperceptible, barely noticeable above the mic hiss. Yesterday I thought it was perfect, but re-testing has shown it's not. This is disappointing. Now I'm wondering how to remove the last bit of noise?
    There is a noise reduction plug in in Reaper, not used that one but I have had good results with one in Abobe Audition 1.5. These noise reducers can product artefacts in the wanted signal and work best when the noise is low level and you don't need heavy treatment. Do you sir?

    For the future CM Series : 1 to 60 Amps Small Size Toroidal Common Mode Inductors : CWS Coil Winding Specialist, manufacturer of transformers, inductors, coils and chokes One of those toroidal filters with caps each side could replace or augment the 3r3 Ohm stoppers. You can just buy a core and wind your own, a good source of solid wire is old CAT5 cable.

    Dave.

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    I tried noise reduction, not in Reaper but in Audacity, to reduce this noise in one film scene which I recently did in a very quiet environment where the noise was very noticeable. The noise reduction worked very well for the 1kHz component of the noise, but didn't touch the clicking noise. I removed that in the spaces between the actors talking by simply cutting out the piece of soundtrack where the click occurred, and replacing it with a bit of noiseless soundtrack. Very laborious, but it worked.

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