Audio Reviewer Becomes Distressed When his Blind Test Fails to Show Expensive USB Cable is the Best

[DanielT]

Any cable that affects jitter or digital waveform indecisiveness is bound to have reactance that is undesirable for proper operation.

But jitter in modern, normally decently constructed DACs, which in principle most I believe and assume are is no longer a problem.If I got it right. Far far below the level of audibility. Could not link pdfn but it can be googled, see picture.

 

[MC_RME]

I do not think his presentation about jitter is correct. This is from that article.

View attachment 152026

This seems to imply that some clock jitter on the wire in the data corresponds to DAC jitter that results in AC waveform distortion. I do not believe that is true. Some DAC chips with built-in USB do try to recover the audio clock from the embedded signal, but that is really an issue with the device's clock. I thought that all good DACs use their own high-quality clock isolated from the I2S or USB clock.

This is from the USB 2.0 standard, page 67, when discussing isochronous transfers (I added the bold):



USB is not simple TTL signaling, like that article shows. It is a NRZI encoding of multiple voltage levels that yield different eye diagrams depending on the USB version.

The article is about USBC (usb 4). USB 4 is nothing like early USB. It is Reed-Solomon FEC encoded, which means the bits are scrambled. USB 4 interfaces have re-timers in them between the cable and a DC-blocking capacitive coupler and the host buffer. It uses a spread-spectrum signal. I believe all the services, like isochronous transfer, are handled by upper layers. They no longer exist on the wire as separate signaling.

I'm not a USB implementor, so maybe I'm missing something here.

Marc

The diagram is correct. It is not about USB. It's about clocking a DAC chip.

Also the article has been written 2018. It is NOT about USB 4. Not at all.

You seem to have misunderstood parts of it.

 

[radix]

The diagram is correct. It is not about USB. It's about clocking a DAC chip.

Also the article has been written 2018. It is NOT about USB 4. Not at all.

You seem to have misunderstood parts of it.

Ok, I see it is about USB 3.1. USB 3.1 is also scrambled then encoded as 8/10 or 128/132. There's no direct correlation of the recovered modulation clock to the output bit timing. The bits have to be recovered from the 8/10 or 128/132 first, then descrambled from a local buffer. My point about the modulation is that the bits on the wire are clocked and encoded entirely differently than the audio samples. The audio clock is referenced from a master clock via clock synchronization protocols to sampling clocks on the DAC. A different cable is not going to make a difference (assuming they are all within spec).

The figure I copied looked like it was making a direct comparison to data clock jitter and DAC clock jitter, and the earlier figure in the article makes it look like you have the same bits and waveform everywhere. I guess I don't understand it.

Marc

 

[sq225917]

Radix, The image you linked to erroneously implies that jitter causes uncertainty as to what a bit is meant to be, 0 or a 1. It doesn't, it just creates uncertainty about the timing and therefore frequency of any encoded signal.

There's no usb 3 or 4 chipsets on any dac, so no point discussing transmission protocols that aren't used In audio.

 

[mslim]

Is it just me or does audiophile nonsense sound just a bit more rational when uttered by a British accent?

Australian accent...... so no. LOL. British perhaps..

 

[tomtoo]

Yes, a believe system can completly knock out the logic department of the brain.
But thats not new.

 

[Sgt. Ear Ache]

One thing to remember about blind testing - it doesn't preclude you from imagining you hear a difference between two things. You do make a choice...and you can still totally imagine you're hearing a difference. The blindness just prevents you from using other senses to bias your imagination in favor of one or the other choice. When this guy took the test he probably thought he was able to identify the differences he was expecting to hear - although he may have experienced some dawning horror at the discovery that the choice wasn't nearly as clear as he thought it would be. The actual choices he made showed that the difference he thought he was hearing was imaginary. When these audiophiles talk about their subjective impressions of the sonic differences, they often talk about things that should be obvious in a blind abx test. They aren't talking about incredibly subtle, difficult to distinguish stuff. They are talking about stuff that is so obvious to them they can hear the difference in comparison to some other component they listened to several hours or days or weeks ago. It's laughable.

Honestly, I think pretty much every audio product review should include some blind abx testing. It won't happen of course...it would totally change the industry.

 

[Promit]

One of the things this guy mentions is that when you are switching and doing A/B testing, you're primed to hear a difference and can force yourself into doing so. That's actually a very good point! This is of course why we either do ABX testing, or sometimes you don't switch. In the ultimate case, you see if someone reports differences but never actually change anything. You don't just go A/B/A/B/A/B because you'll still bias towards hearing something if you know whether you're listening to A or B.

 

[egellings]

He believes he hears a difference. That's all it takes to "hear" one for a subjectivist.

 

[Madjalapeno]

I was just looking for a short USB-A to USB-B cable for my DAC. I want it to look nice, be about 12" long, and as long as it's to spec I'm happy.

Amongst the suggestions was this - https://smile.amazon.com/AudioQuest-Carbon-USB-B-Plug-0-75m/dp/B0041EH0WW/ - so many people convince themselves it has to be better.

 

[DanielT]

Who knows he might get a visit from:

 

[Jimbob54]

Is it just me or does audiophile nonsense sound just a bit more rational when uttered by a British accent?

Isn't he Australian?

 

[HiFidFan]

Isn't he Australian?

Some here need to catch up

 

[Jimbob54]

Some here need to catch up

Usual scenario, "jump to new" and I get sucked in not realising there is 3 pages of chat after that

For British cable bollocks try this guy

 

[DanielT]

Usual scenario, "jump to new" and I get sucked in not realising there is 3 pages of chat after that

For British cable bollocks try this guy

But what is it about these people? Why do they force their ususpecting wife into their blind tests? His wife listened blindly for 90 minutes!

Could it be that he indicated via tone, body language, etc. what she would think about the sound in the various cables? It's easier than you think to be affected in this way.

 

[amirm]

Could it be that he indicated via tone, body language, etc. what she would think about the sound in the various cables?

It could be anything. Shame he didn't record that interaction so we could judge how "exact" his wife described the sound as opposed to how much he read into her comments.

 

[antcollinet]

Many wives:

"I know what he wants to hear - I'll just tell him that. Anything for a quiet life"




Not mine though. If I even suggested something similar, she'd look at me as though I'd lost my mind, and wander off shaking her head

 

[sq225917]

I was just looking for a short USB-A to USB-B cable for my DAC.

I can sell you a 50cm, Hama.de certified, usb cable for £15 plus p&p. I guarantee that's there's technically no better cable. I don't thibk anyone still does certified cables these days. I stocked up years ago.

 

[Madjalapeno]

I can sell you a 50cm, Hama.de certified, usb cable for £15 plus p&p. I guarantee that's there's technically no better cable. I don't thibk anyone still does certified cables these days. I stocked up years ago.

I'm all set, thank you though.

 

[mslim]

One of the things this guy mentions is that when you are switching and doing A/B testing, you're primed to hear a difference and can force yourself into doing so. That's actually a very good point! This is of course why we either do ABX testing, or sometimes you don't switch. In the ultimate case, you see if someone reports differences but never actually change anything. You don't just go A/B/A/B/A/B because you'll still bias towards hearing something if you know whether you're listening to A or B.

That is why you need to do it over a statistically meaningful number of times in a controlled manner.