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Posted by jakdedert on 03/31/06 21:43
Rick Merrill wrote:
> jakdedert wrote:
>> mv@movingvision.co.uk wrote:
>>
>>> In message <1143805585.304897.289310@u72g2000cwu.googlegroups.com>,
>>> Oleg Kaizerman <KAIZERO1@gmail.com> writes
>>>
>>>> pd150 or 170 do not have automatic level control
>>>> they have fixed input stage with hard limiter around-1 dbfs
>>>> common mistake .
>>>> alc its wrong term only
>>>> the Panasonic 100 also has the same structure but without fixed input
>>>> stage m the limiter kicks at -6 dbfs till -4.5 (ganged)
>>>>
>>>
>>> Oleg dear chap, you're being pedantic to a fault. Of course the PD's
>>> have, for all practical purposes, automatic audio level response with
>>> options for 0db limiter/cut off.
>>>
>>> Nevertheless the issue is one of using an external mixer, such as an
>>> SQN, as a means of over riding, to a significant degree, the cameras
>>> auto level response using the cameras proportional responsiveness to
>>> such an input.
>>
>>
>> There is a significant difference. ALC is exactly what it says:
>> Automatic Level Control. IOW, it raises the gain for quiet inputs,
>> and lowers it for louder signals...leaving everything squashed within
>> a narrow dynamic range. A hard limiter does nothing at all to the
>> signal until it reaches a preset level, then chokes it off (in a
>> usually unfriendly fashion).
>>
>> However, given that the it does nothing until then, it's only a matter
>> of keeping the input below that threshold to get decent recorded
>> dynamics. That can be done with a mixer or even a simple level
>> control between the mic and camera. Some experimentation is in order
>> to stay below the threshold, but overall, it's good news for the OP.
>>
>> A 'sort of' ALC can be achieved with a limiter by raising the gain of
>> the mic to the point that almost any audible sound will hit the
>> limiter threshold; but it's not true ALC, which is variable.
>>
>> jak
>
> Suppose one were to raise the gain of Just One Channel (e.g. the right
> channel of a stereo input) - would that force the ALC (I'm unclear on
> the diff. from AGC) to be a constant?
>
>
Probably, but the key is to stay below the threshold...either channel.
BTW, AGC = ALC: Automatic Level Control / Automatic Gain Control...same
thing, although AGC is used more in RF and video, IIRC.
jak
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