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Old 2nd November 2004, 11:03 AM   #1
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Default Digital volume control

Hello.How to adjust digital signal(volume)?How to make digital volume?
regards
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Old 2nd November 2004, 12:41 PM   #2
gmarsh is online now gmarsh  Canada
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The PGA2310/2311/4311 chips from TI are very good.

I've tried using a MAX5437 digital pot in the past, but the results were awful - the Audio Precision gear gave it a THD approaching 1%. But there's probably better pots out there...
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Old 2nd November 2004, 01:27 PM   #3
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thanx a lot...
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Old 2nd November 2004, 03:08 PM   #4
hacknet is offline hacknet  Singapore
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is there anyway to get it to work with a micropro?
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Old 2nd November 2004, 03:58 PM   #5
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I saw characteristics for pga chips.
I don't need to adjust analog signal digitaly.I need something to adjust digital signal.
Example:
Input is digital>>>volume control>>>output digital
but no conversion to analog present

regards
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Old 3rd November 2004, 12:21 PM   #6
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Usually a DSP is used for control in digital domain. For volume control maybe the DSPIC controller from Microchip would be nice as it could do the job and you could use the same chip for remote controller. In addition you'll need S/PDIF reciever and transmitter chips (see www.cirrus.com).
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Old 3rd November 2004, 06:57 PM   #7
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Quote:
Originally posted by mhelin
Usually a DSP is used for control in digital domain. For volume control maybe the DSPIC controller from Microchip would be nice as it could do the job and you could use the same chip for remote controller. In addition you'll need S/PDIF reciever and transmitter chips (see www.cirrus.com).
Deserialize, multiply, dither and serialize in a 30MHz PIC.Even trickier with greater than 16 bit data. And a bit of rc stuff thrown in. Hope you're not worried about latency.
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Old 4th November 2004, 09:11 AM   #8
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thanx guys very much.
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Old 8th November 2004, 04:00 PM   #9
gmarsh is online now gmarsh  Canada
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Quote:
Originally posted by rfbrw


Deserialize, multiply, dither and serialize in a 30MHz PIC.Even trickier with greater than 16 bit data. And a bit of rc stuff thrown in. Hope you're not worried about latency.
Can't be that hard - I've written DSP code on an ancient Motorola DSP that does far more stuff with an even lower instruction rate.

Here's what you need...

deserialize - handled by a dsPIC's codec interface.
multiply - 1 or 2 multiplies per instruction, depending on 16 or 32 bit data (assuming a 16 bit scale factor). Multiply by 2 for 2 channels.
dither - 2 multiplies, a couple of shifts and a few adds to update a LCG generator, generate a triangle PDF and sum it into the signal. You can use the same dither data for both channels.
serialize - again, handled by hardware.

With a 30MHz core clock, manipulating a 44KHz (or even 96KHz) audio stream still gives you plenty of spare clock cycles.
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Old 9th November 2004, 12:35 AM   #10
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somebody plz put a price/bom on these dsp solutions
$1000?
$100?
$10?
$1?
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