Objective-Fi Optical Networking & SFPs

[pkane2001]

1 hour ago, cat6man said:

 

i personally define objective proof in audio as requiring measurements that confirm a hypothesis.

i do not include blind or double blind testing as 'objective' (your mileage may vary)

so let's continue on my version of a possibly 'objective' answer.

any engineers or scientists here?

 

i'll assume the audio precision top end stuff is sufficiently accurate (correct me if that is not right).

 

now, can the audioprecision (or other) equipment collect a histogram of DAC output as well as instantaneous peak errors or just averages?  when it plots snr vs. frequency for a single or multi-tone test, can it save peak or just average noise?

 

if so, can anyone point me to published material where the average vs. instantaneous and peak distortions are shown?

 

I have a feeling we've had this discussion before. First, you don't have to use FFTs to average the results. Use peak-hold or maximum value, instead. Any sudden temporary peaks will be present in the spectrum.

 

Second, you don't have to do the comparison in the frequency domain, you could do it all in the time domain. Exactly what DeltaWave software does: take two signals and subtract them so as to find the difference. No averages used and any instantaneous peak errors will become obvious. It computes all kinds of metrics from this, including jitter, group delay, linearity, etc., etc. or just zoom-in on the difference waveform. Look at the individual samples, if you want, or look at it in the frequency domain, on a phase plot, or a spectrogram. It'll even tell you how close to bit-perfect the capture is.

[pkane2001]

3 hours ago, Audiophile Neuroscience said:

 

I agree it seems to be assumed by some as fairly simple and infallible procedure, or at least highly validated, and can even be used by amateurs as a weapon to push a particular view. It is just a test tool and as alluded to above, like all tools, one needs to know how good the tool is at telling you what you think it is telling you - in the context and setting of the whole test methodology .........I think we are heading OT.....

 

All things being equal, DBTs are better than sighted testing, unless you are testing for confirmation bias or a placebo effect. Whether DBTs are infallible or not is not a question, at least in my mind. Of course they can be done wrong, and the results may not be accurate. It's important to understand the limitations and follow a proper test design.

 

But, it's an audio malpractice, IMHO, to deny that DBTs can, with proper controls, produce a much more accurate, repeatable and reproducible result than sighted testing. And such controls are not voodoo or a mystery. They are studied, reported and well documented.

 

A sighted test cannot be done right: there's no way to eliminate or separate the effect of biases related to other senses and preconceived ideas and knowledge. A DBT can be done wrong, but when properly planned and conducted, it is a scientific instrument that can be measured and calibrated.