To S. Andrea Sundaram,
I enjoyed your well-written article about digital volume controls. I run a Wyred 4 Sound DAC-2 (a 32-bit DAC) directly into a pair of Wyred 4 Sound mAMPs. I cannot hear any loss of resolution over a large range of attenuation (0 to -40dB). And it sounds superior in every way compared to using a very high-quality analog preamp.
I would like to point out that 24-bit and 32-bit DACs are more marketing than reality. The intermediate processing may be done in 24 or 32 bits, but the final resolution of a DAC is only around 22 bits due to the S/N ratio of about 130dB (thermal noise issues). The best of the DACs today can achieve only 21 or maybe 22 bits of resolution. That still gives about 6 bits of attenuation before any theoretical resolution loss occurs with 16-bit material. That is quite a range: 36dB. In practice, I don't hear any resolution loss until I drop below -45dB.
I am thrilled by the advances in digital audio (DACs, class-D amps) during the 21st century. Digital is no longer a dirty word. Modern DACs and class-D amps are closing the gap with analog playback and class-A amps, respectively, and at a huge savings in cost and power consumption!
Cheers,
Gautam
Since most modern DACs perform some mathematical manipulations of the audio signal -- and must do so, if you are using digital volume control -- a 24- or 32-bit data path means that those calculations will be done to greater precision than if the DAC used fewer bits. Ultimately, the result is higher fidelity -- even though it doesn't show up in simple numbers like dynamic range or signal-to-noise ratio. The title of the article -- "What's Wrong with Digital Volume Controls?" -- was chosen to generate interest. The conclusion -- as you read, and as your experience suggests, is that there is nothing wrong with them -- provided they are properly implemented on a DAC with suitably high SNR. I still find that analog and class A have the edge, but I agree that digital technologies have made tremendous strides toward closing that gap. . . . S. Andrea Sundaram
