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So, what would the operator of this thing use to control this mixer? Would
it still have dials and slide controls like normal mixers do, or would it
be hooked in a computer, or what? I thought some mixers had the ability to
set presets, and motorized controls would give a tactile representation of
where the controls end up when buttons are pressed.
At 07:25 PM 8/1/01 -0400, you wrote:
>
>
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> = be more selective when quoting text =
> ===================================================
>
>Here are some sites that have information on the LM1973 audio mixer
>chip.
>
>http://search.dogpile.com/texis/search?q=LM1973&geo=no&fs=web
>
>Timothy Stockman wrote:
>>
>> >|3. Adjust levels *before* the A/D to prevent overload while
maximizing dynamic
>> >| range. Most modern MD recorders have fixed gain *berfore* the A/D;
not a
>> >| good thing!
>>
>> >Absolutely. So you use the LM1973's you mentioned in a programmable gain
>> >configuration, right? Are these parts quiet enough to work with
>> >microphone-level signals?
>>
>> I was planning on using a topology that had the LM1973 in the *feedback*
loop
>> of the microphone preamp stage. Therefore, it would get its drive from
the output
>> of the mic preamp, after 40 dB or so of gain and attenuate it back to
microphone
>> level before feeding it to the inverting input. They spec these chips
at over 100 dB
>> S/N, and this configuration exploits the available S/N to the max, so my
guess is
>> that it would be quite acceptable. This topology is what I was refering
to when I
>> was talking about channel trim.
>>
>> The LM1973 contains three pots; I'd use the first one for level trim as
described\
>> above, and the other two as conventional attenuators, one feeding the left
>> channel and one feeding the right. That would allow the controlling
microprocessor
>> to emulate channel gain and pan, all the while maintaing an optimum gain
>> structure to maximize S/N while minimizing overload.
>>
>> >you're well over
>> >1/2 watt--roughly 20 hrs. with 3-4 AA cells-- is this what you have in
mind
>> >for a portable MD system?
>>
>> That would be great... I'd planned to use NiHM AA cells...
>>
>> >Also, I would think that some MD titling interface built into the mixer
>> >might be a nice feature that would distinguish your mixer from anything
else
>> >that's commercially available.
>>
>> A great idea! I'd probably use an 8051 derivative (we've had great success
>> here at work with the Philips 87c552 in battery powered equiopment; it has
>> some nifty power-save and sleep modes). This CPU would probably have
>> enough resources left over to run a titling program.
>>
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>
>--
>Jim Coon
>Not just another pretty mandolin picker.
>mailto:[EMAIL PROTECTED]
>If Gibson made cars, would they sound so sweet?
>
>My first web page
>
>http://www.tir.com/~liteways
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