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I'm guessing that the AIC23 is AC coupled. Does anyone know at what
frequencies this audio codec begin to induce phase shifts? Would below
40Hz be a reasonable assumption? Lower still perhaps?

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a...@yahoo.com (Àine Canby) wrote in message news:<5...@posting.google.com>...
> I'm guessing that the AIC23 is AC coupled. Does anyone know at what
> frequencies this audio codec begin to induce phase shifts? Would below
> 40Hz be a reasonable assumption? Lower still perhaps?


I can use an all-pass filter to fix the phase distortion for low
frequency signals, correct?

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Àine Canby wrote:
> 
> I'm guessing that the AIC23 is AC coupled. Does anyone know at what
> frequencies this audio codec begin to induce phase shifts? Would below
> 40Hz be a reasonable assumption? Lower still perhaps?

Is a data sheet available?

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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Jerry Avins <j...@ieee.org> wrote in news:3...@ieee.org:

> Àine Canby wrote:
>> 
>> I'm guessing that the AIC23 is AC coupled. Does anyone know at what
>> frequencies this audio codec begin to induce phase shifts? Would below
>> 40Hz be a reasonable assumption? Lower still perhaps?
> 
> Is a data sheet available?
> 
> Jerry


The full part number is TLV320AIC23 (TI). This part is very similar to the 
Wolfson WM8731. (Pins 21 & 22 are swapped).

It operates on a single supply. Like virtually all new audio converters it 
assumes AC response. Usually the lower frequency limit is determined by the 
external capacitors. 


-- 
Al Clark
Danville Signal Processing, Inc.
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Available at http://www.danvillesignal.com

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>I can use an all-pass filter to fix the phase distortion for low
>frequency signals, correct?

I would rather build a amplitude equalizer which also linearizes the
phase. Say you have 10Hz -3dB cutoff and want to shift that to 2Hz, so
you must apply 15dB gain (10/2) at 2Hz. One implements that filter as
IIR filter, so one needs rather much footroom. Other people can tell
you more about the different IIR filter forms. 

One could also use bigger capacitors in the inputs. If you have the
AIC23 datasheet you should also watch out for a highpass on the
digital side, which codecs often have nowadays in order to fix
possible DC offset caused by the input stage of the A/D-C.

Uli

-- 
------- http://grassomusic.de -------

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