Taking out the garbage
I mentioned in yesterday’s post it’s not a good idea to rely upon a low pass filter to reduce transient input problems if it is in the feedback loop of an output stage. The raw output of a DAC chip has lots of high frequency components that can agitate an output stage into sounding aggressive, bright, and unpleasant. The unfortunate proof of this can be found in DACs of all prices.
Modern DAC chips have more high frequency garbage than those of old because of higher sample rates for PCM, and greater noise levels with DSD. The stress on output stages following the DAC chips are at an all time high.
One simple method of reducing the stress on output stages is the use of a simple, passive filter between the DAC and the output stage. The chain would look like this: DAC raw output->passive low pass filter->output stage. Passive filters do not get upset by what you feed into them. Their output is simply a function of their configuration.
Why is this method preferable to redesigning the output amplifier to be less affected by its input? Because pre-cleaning noise allows the output amplifier to be designed with best sound first, immunity to noise second. The end result is a much better sounding output stage, free of transient overload.
Both methods work and measure well. It is the sonic differences that matter and those engineers that listen to their designs will nearly always triumph over the technologists who just measure.
It sure ain’t all the same
Yesterday we sharpened our understanding of why the multitude of digital storage mechanisms sound different despite the fact they produce the same data. What we learned is that while the data may be identical, its timing, noise levels, and quality presented to our DAC is not. In the same way we likely would not question why different turntables do not produce the same results, despite the fact they spin at the same speeds, it should not be too great a surprise when our digital systems produce unique sonic signatures.
So the question I would next ask myself is this: what’s the best storage and delivery system for me? And the answer is a tough one to give in clear form, because the truth is that none are perfect and all have their issues. For example, using a memory player like our own PWT narrows the differences between optical storage media and hard or soft drives to the point of near confusion. But the PWT can be bettered by the proper implementation of a soft drive in the right computer setup, and the opposite is easily true.
Here’s the bottom line: digital storage mediums, like their analog counterparts, are completely at the mercy of connected equipment to produce a final outcome. Thus, no blanket statement can be made unless it includes the entire chain. We all want the silver bullet: this drive sounds better than that drive but the truth is more elusive than that. The bullet does not exist alone in a vacuum.
We are getting set to release our first album and we are excited. But how shall we present the data to our customers so they might hear it in all its glory? Downloads? Specially mastered CD? DSD high resolution? SACD? DSD or PCM? You get the point. For some who have optimized their CD based systems, the answer is obvious. For others, who have managed to produce stunning results from their solid state drives and computers, their solution is different again.
Bottom line? We have to be open to producing media in enough formats that makes the choice to optimize performance an easy one for those of us that have grown comfortable for which is better. And so far, for me, the physical disc reigns supreme.