What about 32 bit DACs

What about 32 bit DACs

A DAC is a circuit that converts digital measures of audio amplitude in discrete steps into a continuous analog electrical equivalent of the sound to be reproduced. We have been taught to associate the number of bits in that digital word with the quality of the calculation, but the rate of the converter also comes into play. If we do conversion at 16 bits, 48,000 times per second, it is not the same as doing conversion at 16 bits and 96,000 times per second. Along comes 1 bit DACs and SACD that convert at a much higher rates and the whole idea of performance and bit depth falls apart. But in a ladder DAC like MSB uses, the performance of the DAC is directly linked to the precision of the ladder, and the number of bits in that ladder are critical.

MSB has been shipping a true 24 bit DAC for many years, and now has produced a true 26 bit DAC in the Diamond DAC IV. But we are now facing bold product claims about new 32 bit DAC's. These are DAC chips just like any other from Burr Brown, AKM or Analog Devices. Lets look a little deeper to avoid any confusion about what these DACs actually are.

Here is what a typical web site says. “The advantage of using this 32-bit process to reconstruct a 16-bit digital signal (i.e. Redbook CD) is simple; This process interpolates the digital information more accurately by calculating the finer steps with 32-bit resolution that were lost during the analog-to-digital 16-bit mastering process.

Notice that they use the word “process “ not DAC. Notice they talk about “reconstruct “ and “interpolate “ - both digital terms, not analog conversion. All this is saying is that they are using a digital filter with “32 bit resolution “ to do their math.

Looking into a typical Datasheet: Input resolution is 32 bit. Digital filter: 32 bit architecture. Thats all it has to say except it has a THD of -110 dB. So what is the DAC technology? They do not even say!

We dig deeper and find it is a delta sigma DAC just like everyone else's. Then we find this quote. “After all the DSP and complex noise shaping of the signal is complete the digital number must be converted to an analog output. In principle the typically six bit number may be applied to a six bit DAC and the analog output is produced.

So the hot new 32 bit DACs are actually 6 bit DACs with a 32 bit digital filter. It is undoubtably a good DAC for the market it was designed for. The MSB digital filter runs at 80 bit resolution and the MSB DACs are 24 or more bits.

So be informed and do not be fooled by the over-the-top advertising made by the audio companies who actually use these Delta Sigma chips.