Digital volume control

[DJ_Looly]

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

 

[gmarsh]

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]

thanx a lot...

 

[hacknet]

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

 

[DJ_Looly]

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]

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]

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]

thanx guys very much.

 

[gmarsh]

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]

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

 

[rfbrw]

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.

It isn't hard, just that if the dspics do that 1 instruction cycle = 4 clock cycles thing, it might prove a little slow.

 

[jhenderson01075]

I use the Roland M1000 mixer as a digital volume control on my stereo. It also acts in the capacity of a pre-amp switcher, allowing me to listen to CD player, or PC via it's USB connection.

For 16-bit music sources, such as Redbook CDs, up to 45 dB of digital attenuation is completely lossless using the M1000.

 

[amp_guy]

digital volume pot

re. digital volume control

look at the dallas semi ds1802.
ihave a hand full but havent tried them yet
they can be used without a cpu just a couple of pushbuttons
so no clock noise to deal with.
look on their site they have a report of some testing done with audio precision gear that looks pretty respectable.

 

[gmarsh]

It isn't hard, just that if the dspics do that 1 instruction cycle = 4 clock cycles thing, it might prove a little slow.

AFAIK, the dsPICs are 1 instruction per clock.

 

[apollyon25]

alternative to DSP

Hi,

Try a Cygnal (now Silicon Labs) micro. 8051 core (C with Keil) and runs at 25MIPS!

apollyon25

 

[Rookie]

TI's SRC4193 would be the simplest solution. It is a stereo asynchronous sample rate converter, but has a built-in digital volume control (0dB to -127.5dB, 0.5dB steps). It needs a microcontroler for controling. I'm not sure, but I think that the input/output sampling ratio can be set to 1:1 (44.1kHz input, 44.1kHz output).

 

[Ryssen]

I use the Roland M1000 mixer as a digital volume control on my stereo

How is the M-1000 compared to a usual volpot.as good as or better?

 

[Ryssen]

What I mean is,I have a DCX2496 is it better to use a M-1000 inbetween the CD and the DCX2496 as a digital vol,kontrol,or an ordinary alps pot after the DCX2496.