Are we measuring enough parameters?

[AweLoi]

I was reading an interview with John Siau, chief designer at Benchmark and he was asked if he had ever learned something from a subjective test that was not captured by measurements. Here is his answer:

"A few years back I was evaluating an asynchronous sample rate conversion chip (ASRC) and I noticed a difference when I switched the chip in and out in a listening test. The music sounded brighter when the chip was inserted. The measurements showed a ruler-flat frequency response with THD+N well below the threshold of hearing in our playback system. Additional measurements confirmed that there was no change in the transient response. Something was happening, but we could not see it in the measurements. Eventually, we were able to prove that the audible difference was caused by the clipping of intersample peaks that exceeded 0 dBFS. The DSP in the ASRC was clipping intersample peaks and this added the impression of brightness. We now have a test signal that we can use to measure this defect which can occur whenever a digital source is upsampled. Starting with the DAC2, all of our sigma-delta D/A converters have an “extra” 3 dB of DSP headroom in order to accommodate the highest possible intersample peaks. The elimination of intersample clipping is a gamechanger, but most of our competitors still seem to be ignoring this problem."

Reading his answer showed that yes, measurements do tell the whole story, but only if we are measuring everything needed and that it is possible that we think that we are aware of everything while we are in fact not. Since I am not very knowable when it comes to the technical aspect of audio measurements I wonder if Amir is taking the extra db headroom into consideration when he is measuring DACs or not?

 

[NTK]

Adding the inter-sample peak test has been proposed and discussed. I would summarize the outcome as "inconclusive". Other perhaps will disagree.

Let's develop an ASR inter-sample test procedure for DACs!

Hi there, It's been a while since I thought about this, but why aren't DACs tested for their ability to handle inter-sample overs (or ISP, inter-sample peaks) in ASR reviews? Here are some established facts: ISPs are very real, and almost any material that's been released after the 90's can...

www.audiosciencereview.com

 

[AweLoi]

Adding the inter-sample peak test has been proposed and discussed. I would summarize the outcome as "inconclusive". Other perhaps will disagree.

Let's develop an ASR inter-sample test procedure for DACs!

Hi there, It's been a while since I thought about this, but why aren't DACs tested for their ability to handle inter-sample overs (or ISP, inter-sample peaks) in ASR reviews? Here are some established facts: ISPs are very real, and almost any material that's been released after the 90's can...

www.audiosciencereview.com

Thank you! Exactly the answer I was looking for. Looks like it´s easy to remedy if you have a digital volume control on your DAC. My DAC do not have a volume control though. Benchmark and RME both seems to have taken care of this potential problem.

I own a MiniDSP Studio placed before my DAC. It has a digital volume control. When using Dirac it automatically lowers the volume to -10db to give headroom for Dirac. Could I use the volume control on my MiniDSP and set it to -13db to handle inter-sample peaks as well?

 

[NTK]

I think if Dirac already lowers the volume by 10 dB, it would be unnecessary to lower another 3 dB to avoid inter-sample overs.

 

[ppataki]

What I do to prevent any type of clipping is that I use 64-bit digital volume control upstream (i.e. that is the first DSP item in the signal chain in Jriver)

This also allows me to set the volume of all other DSP items (plugins, including Dirac Live) in the signal chain to 0dB, avoiding the risk of decreasing the dynamic range due to lower resolution volume control in those

 

[AnalogSteph]

I think if Dirac already lowers the volume by 10 dB, it would be unnecessary to lower another 3 dB to avoid inter-sample overs.

Along the same lines, using playback volume normalization (e.g. ReplayGain) tends to take care of these concerns as well - pretty much without fail, the material that has real issues with overs is mastered very hot, usually from the time before oversampling brickwall limiters became commonplace (2012ish).

 

[617]

The only valid test of sound quality is a perceptual test.

Our technical tests poorly correlate to sound quality, or only correlate tangentially. Every technical test you see on this website contains a huge amount of information irrelevant to perception and only a small amount of information that may correlate to perception.

These tests are useful for other things, like quality control.

So no, we are not measuring the correct things, but more technical tests are not the answer.

Audio companies cannot be trusted as authorities on the process of assessing sound quality. They have an enormous incentive to differentiate their products and history has shown that they will rely on extremely minute or dubious differences to do so.

It is a fact that in 99.9% of cases nobody will ever be able to tell the difference between a benchmark DAC and any other non broken DAC based on sound quality. For amplifiers it might be 98% simply because they can distort if pushed enough.

Perfect audio electronics are essentially commodities like wheat or nitrogen. Innovation in this space is not going to come from sound quality, it will come from feature set, price, durability, aesthetics and pride of ownership. Benchmark is quite competitive in most of these categories.