Advantage of multiple 1-bit audio DACs?

[jrichrds]

My Discman has a single 1-bit D/A, my room stereo has dual 1-bit D/A, and my car stereo has quad 1-bit D/A. What's the advantage in the latter?

 

[Lynx516]

You realy sure they are 1 bit DACs as that makes no sence what so ever

 

[Fallen Kell]

I think you might have read it wrong and that it said 1 DAC, not a 1 bit DAC.... As Lynx516 is correct, a 1 bit DAC does not make any sense.

Basically think of it in this sense. If this was a 1 bit DAC, there would be 2 settings on or off. In sound terms that would be the same thing, loud or nothing. If you want to visuallize it think in terms of black and white. Either there is something there, or there isn't anything.

Now the difference in using a quad DAC verses a 1 bit DAC would be easiest to again visuallize it in terms of graphics. It would be the difference between looking at a picture in true black and white (i.e. no gray scale) or a picture with 16 colors.

 

[AbsolutDealage]

1-bit DAC = a Comparator, which makes no sense as Lynx and Fallen pointed out.

 

[Lynx516]

1 bit DAC doesnt = a comparator it = a wire

 

[Lynx516]

Ok after looking into this a 1 bit DAC does actually exist. though it isnt a normal DAC. What it does is it notices the change in energy in the signal that enters it and then outputs a pulse that coresponds to the average of the input. This takes advantage of the human ears inability to detect difference in phase and then outputs. It is not the most elegant solution. I assume having 4 1 bit DACs enable a higher quality of sound because I assume the system splits the signal up bettween them but that is alot of assuming on my behalf.

Edit: a 1 bit DAC shoudl be called a Delta Sigma modulator. this page describes in detail the cuirctity of one. Link

 

[AbsolutDealage]

Originally posted by: Lynx516
Ok after looking into this a 1 bit DAC does actually exist. though it isnt a normal DAC. What it does is it notices the change in energy in the signal that enters it and then outputs a pulse that coresponds to the average of the input. This takes advantage of the human ears inability to detect difference in phase and then outputs. It is not the most elegant solution. I assume having 4 1 bit DACs enable a higher quality of sound because I assume the system splits the signal up bettween them but that is alot of assuming on my behalf.

Edit: a 1 bit DAC shoudl be called a Delta Sigma modulator. this page describes in detail the cuirctity of one. Link

Ahhhh... that makes more sense.

1 bit DAC doesnt = a comparator it = a wire

Oh yea... I was thinking ADC... I need to start paying attention.

 

[Mark R]

'1-bit' is just the marketing name for a delta-sigma modulator. The modulator essentially uses a very fast low-precision DAC (usually 1 bit, but sometimes as much as 4 bits) and a processor that converts low-frequency high-precision sample data into high-speed low precision data. There are practical problems with making high precision DACs/ADCs, and 'conventional' high-precision DACs and ADCs are considerably more expensive than delta-sigma devices and despite this usually only offer a maximum precision of 16 or 18 bits. The disadvantages of phase shift, high-frequency noise and time delay are not significant in audio devices - as a result virtually all 'audio' DACs, these days, are delta-sigma modulator types.

To improve performance further it is possible to 'daisy chain' several modulators together - to give better resolution and frequency range. Modern 3 or 4 stage delta-sigma DACs are capable of accepting a 24-bit 192 kHz signal and outputting a signal with 22-usable bits of dynamic range.

 

[blahblah99]

1-bit dac doesn't mean its a 1-bit DAC in the usual sense... it just means the type of architecture that is in the DAC... in this case, sigma-delta.

 

[Howard]

http://www.sharp-usa.com/products/ModelLanding/0,1058,302,00.html

 

[mAdD INDIAN]

How hard would it be to make a very simple DAC or ADC using digital logic and CAD software (such as Altera Quartus)??


Also is it possible to make simple sounds by moving the switches (connected to a board with the Altera FLEX chip that we use)?

 

[Mark R]

You could make a very crude DAC with a PWM output and a suitable analogue Low-pass filter.

ADC is a bit more problematic and you can't make one simply from digital logic. You certainly won't be able to build one that costs less than an equivalent off-the-shelf part - unless you want something extremely specialised.