Digital volume control

DJ_Looly · 2nd November 2004, 10:03 AM

Hello.How to adjust digital signal(volume)?How to make digital volume?
regards

gmarsh · 2nd November 2004, 11:41 AM

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...

DJ_Looly · 2nd November 2004, 12:27 PM

thanx a lot...

hacknet · 2nd November 2004, 02:08 PM

is there anyway to get it to work with a micropro?

DJ_Looly · 2nd November 2004, 02:58 PM

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

mhelin · 3rd November 2004, 11:21 AM

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).

rfbrw · 3rd November 2004, 05:57 PM

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.

DJ_Looly · 4th November 2004, 08:11 AM

thanx guys very much.

gmarsh · 8th November 2004, 03:00 PM

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.

davesaudio · 8th November 2004, 11:35 PM

somebody plz put a price/bom on these dsp solutions
$1000?
$100?
$10?
$1?

2nd November 2004, 10:03 AM	#1
DJ_Looly diyAudio Member Join Date: Nov 2004 Location: Montenegro - Podgorica	Digital volume control Hello.How to adjust digital signal(volume)?How to make digital volume? regards

8th November 2004, 11:35 PM	#10
davesaudio diyAudio Member Join Date: Feb 2003 Location: GTA	somebody plz put a price/bom on these dsp solutions $1000? $100? $10? $1? __________________ intentionally blank

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2nd November 2004, 11:41 AM	#2
gmarsh diyAudio Member Join Date: Apr 2004 Location: Halifax, NS, Canada	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...

2nd November 2004, 12:27 PM	#3
DJ_Looly diyAudio Member Join Date: Nov 2004 Location: Montenegro - Podgorica	thanx a lot...

2nd November 2004, 02:08 PM	#4
hacknet diyAudio Member Join Date: Nov 2002 Location: sg	is there anyway to get it to work with a micropro?

2nd November 2004, 02:58 PM	#5
DJ_Looly diyAudio Member Join Date: Nov 2004 Location: Montenegro - Podgorica	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

3rd November 2004, 11:21 AM	#6
mhelin diyAudio Member Join Date: Apr 2003 Location: Tampere Finland Europe	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).

4th November 2004, 08:11 AM	#8
DJ_Looly diyAudio Member Join Date: Nov 2004 Location: Montenegro - Podgorica	thanx guys very much.

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