digital versus analog volume attenuation

[frdchang]

hello,

i couldn't find a thread regarding this, but would digital volume attenuation be better than analog (like a stepped attenuator) volume control?

if i went about building a DAC would it be best to have the volume control at the DAC level?

thanks,
fred

[CrisTUFR]

I just ran into this today for posting on another forum, so I might as well re-paste it here:

http://pdfserv.maxim-ic.com/en/an/AN1828.pdf

No sense using ADCs/DACs. There are already devices that do the trick for you.

I can't see this approach being any worse than using a stepped attenuator, unless you go all out on the resistors that you choose to use for the attenuator. Even then, I'm not sure the difference is worth the money. :P

If I ever get a chance, I will likely use the parts listed in the app note above and give it a go.

Cheers,

Chris

[frdchang]

hello,


what i'm asking is the digital attenuation of the signal pre-dac stage.

so if a sample is at 175, i attenuate it to 100 etc., then i but that 100 value into the dac, hence an attenuated signal without aditional circuitry.

thanks,
fred

[CrisTUFR]

In this case, it is most certainly better to attenuate in the digital domain if you can. I'm not too sure how to go about this, though.

Perhaps the DAC can do this internally?

Chris

[carlosfm]

Originally posted by CrisTUFR
In this case, it is most certainly better to attenuate in the digital domain if you can.

No, because you loose resolution (bits).
It's not the way to go.

[tiroth]

You lose S/N ratio no matter what you do, digital or analog. There are pros and cons to both methods, although the only really decent digital attenuation will be DSP-based.

I think that as long as we are speaking of 20-30dB max attenuation, a good digital domain attenuator will be just as good as an analog one, especially if it means eliminating buffers etc from the signal path. This is provided we are attenuating 24 bit data.

YMMV.

[frdchang]

hello,

thanks for the reponses:

[CrisTUFR]

Originally posted by carlosfm

No, because you loose resolution (bits).

Good point.

I always opt to do all other types of processing in the digital domain if I can, when the signal is starting off in the digital domain.

Personally, I just know how to do things in the digital domain properly, so I always take that route if I can.

Chris

[Gasho]

I have similar question . In my tube preamp (AR LS8) i have two chips (one for each channel) as electronic attenuator that are microprocessor controled, so I am wondering is this better approach then the classic high quality analogue pots like Alps "Black beauty" or mechanic step atenuattor.

[matt20102]

Why not use a digital variable resistor such as the ones featured here ? I've got several projects in the design phase and most use these as volume controls.