Jump to content

Upgrade Power supply vs cable vs DAC


DomT
 Share

Recommended Posts

13 minutes ago, rabski said:

There is sound science behind the suggestion to make digital coax cable a specific length. I need to look it up or work it out, but it relates to the wavelength and internal signal reflections cancelling or reinforcing.

I posted a link earlier in the thread:

https://positive-feedback.com/Issue14/spdif.htm
 

I agree that it sounds logical but it is intriguing that no DAC or cable manufacturer, pro or foo, has picked up or made reference to it

Link to comment
Share on other sites

36 minutes ago, rabski said:

There is sound science behind the suggestion to make digital coax cable a specific length. I need to look it up or work it out, but it relates to the wavelength and internal signal reflections cancelling or reinforcing.

In the early days when I was starting to look at digital coax cables I did some listening tests of 0.5m, 1m and 2m cables. To me there was a clear progression of sound quality starting from 0.5m, through 1m to 2m which was the best. Best or better in this instance being categorised by being smoother in sound and less fatiguing. However it was a marginal improvement and simply adding 4 ferrites to a shorter cable overtook the benefits of the long cable by quite a margin. So the 20 ferrites that I eventually decided upon was an overwhelming advantage.

I discussed the effect of the longer cable with Rob Watts at the time and who coincidentally had also done a similar experiment with the different lengths of cables. His view was that the length of the cable affected the impedance in the frequency range of the RF noise and this might account for the different sound signatures of the different cable lengths.

  • Like 1
Link to comment
Share on other sites

33 minutes ago, tuga said:

I posted a link earlier in the thread:

https://positive-feedback.com/Issue14/spdif.htm
 

I agree that it sounds logical but it is intriguing that no DAC or cable manufacturer, pro or foo, has picked up or made reference to it

That article concludes by saying, "Once the impedance is accurately matched and the transition times decreased, the Transport will become less sensitive to different digital cables, shorter cables can be used with confidence and the result is cleaner audio with better focus, definition and clarity."

I have highlighted the last three words because in my experience the use of those descriptive words is usually a dead give away for the presence of RF noise induced artifacts giving an initial impression of 'better focus, definition and clarity' but which often becomes fatiguing with extended listening.

  • Upvote 1
Link to comment
Share on other sites

  • Moderator

I suspect different issues are being mixed up here to an extent. There are also a few howlers. Characteristic impedance is not related to the length of a cable, assuming the construction is the same along its length.

  • Upvote 1
Link to comment
Share on other sites

I did not mean to imply characterisic impedance and that is not what I meant and I don't think it is what Rob Watts meant when he described it to me - assuming you are accusing me and Rob Watts of howling at the moon.

Edited by Fourlegs
Link to comment
Share on other sites

Interesting observations and thanks for taking the time to write them.

I've also experienced something similar (but different examples).

In the end though, it all depends on the system context. This can get incredibly complicated once you throw cables and power supply into the mix!

Link to comment
Share on other sites

  • Moderator
Posted (edited)
27 minutes ago, Fourlegs said:

I did not mean to imply characterisic impedance and that is not what I meant and I don't think it is what Rob Watts meant when he described it to me - assuming you are accusing me and Rob Watts of howling at the moon.

No, but there are some comments along those lines. Also, there are a lot of 'may be due to', where there are already perfectly simple and far more likely explanations. I agree with the 'noise' being one, though as the general suggestion is that it comes from the source, then cable length is likely to be irrelevant. The impedance having an effect at RF would be the characteristic impedance, which, as above, is independent of the cable length. Effects from resistance and capacitance are a different issue, but trying to filter RF in this way would be nonsensical, as it would be frequency dependent.

Edited by rabski
Link to comment
Share on other sites

7 minutes ago, rabski said:

No, but there are some comments along those lines. Also, there are a lot of 'may be due to', where there are already perfectly simple and far more likely explanations. I agree with the 'noise' being one, though as the general suggestion it that it comes from the source, then cable length is likely to be irrelevant. The impedance having an effect at RF would be the characteristic impedance, which, as above, is independent of the cable length. Effects from resistance and capacitance are a different issue, but trying to filter RF in this way would be nonsensical, as it would be frequency dependent.

and of course when postulating what difference a digital cable might make to the signal that must also be accompanied with an explanation of how that might affect the sound. Most seem to think just mentioning jitter or some other word is enough in itself.

Many explanations of the process are similar to the South Park explanation as to how to make a profit out of stealing underpants, ie

Phase 1.  Steal underpants.

Phase 2.

Phase 3. Profit.

Our kids loved this show.

  • Haha 1
Link to comment
Share on other sites

  • Moderator

I don't subscribe to the idea that everyone with an interest in hifi is gullible and easy prey for advertising. On the other hand, I have to laugh at the amount of sheer bull droppings abundant, a lot of which revolves around the suggestion that cause automatically means effect. You can spend a lot of time and money eliminating something in the signal chain that is actually already rejected further down the line, or makes no difference anyway. Alternatively, in doing so you can easily ignore something that does have an (unexpected) effect.

Link to comment
Share on other sites

2 hours ago, rabski said:

There is sound science behind the suggestion to make digital coax cable a specific length. I need to look it up or work it out, but it relates to the wavelength and internal signal reflections cancelling or reinforcing.

"The wavelengths of radio waves range from thousands of metres to 30 cm."

https://www.britannica.com/science/radio-wave

If the max wavelength is 30 cm, surely any cable longer than that will not encourage reflections?

Link to comment
Share on other sites

2 hours ago, tuga said:

I posted a link earlier in the thread:

https://positive-feedback.com/Issue14/spdif.htm
 

I agree that it sounds logical but it is intriguing that no DAC or cable manufacturer, pro or foo, has picked up or made reference to it

I read the link (monograph). It reads like an opinion piece. No references to textbooks or research articles are given to back up what he's saying.

Edited by Blzebub
  • Upvote 1
Link to comment
Share on other sites

  • Moderator
4 minutes ago, Blzebub said:

"The wavelengths of radio waves range from thousands of metres to 30 cm."

https://www.britannica.com/science/radio-wave

If the max wavelength is 30 cm, surely any cable longer than that will not encourage reflections?

Reflections within a cable will always occcur. The issue is when they can interract and result in reinforcement or cancellation. This is a perfectly well-known phenomenon in high-frequency work and is a major consideration in designing PCBs for higher frequencies.

The extent of any issue affecting digital transmission in 'our' applications is more likely to depend on the robustness of the signal and the ability of the receiver to reject unwanted signals. For the sake of 'it cannot do any harm', I prefer to keep SPDIF cables at multiples of 1.5m, but frankly it's almost certainly unnecessary.

  • Like 1
  • Upvote 2
Link to comment
Share on other sites

46 minutes ago, Fourlegs said:

and of course when postulating what difference a digital cable might make to the signal that must also be accompanied with an explanation of how that might affect the sound. Most seem to think just mentioning jitter or some other word is enough in itself.

I agree in principle.

With the caveat that there isn't a universal language for characterising sound and thus any description of potential audible attributes can go from explicit through confusing to meaningless depending on the adjectives and the receiving entityphile.

.

I would also add that in my view improvements in performance are always desirable even when not producing audible advantages, unlike many at ASR which believe in "adequate" or "good enough".

  • Upvote 1
Link to comment
Share on other sites

2 hours ago, Fourlegs said:

That article concludes by saying, "Once the impedance is accurately matched and the transition times decreased, the Transport will become less sensitive to different digital cables, shorter cables can be used with confidence and the result is cleaner audio with better focus, definition and clarity."

I have highlighted the last three words because in my experience the use of those descriptive words is usually a dead give away for the presence of RF noise induced artifacts giving an initial impression of 'better focus, definition and clarity' but which often becomes fatiguing with extended listening.

This, in bold, is what I was referring to in my previous post.

There's a huge chance that someone else may not use those descriptive words in the same manner, and thus the "presence of RF noise induced artifacts" is not a given/fact.

Higher fidelity / increased "transparency" / lower noise and distortions will, in my view and experience, produce "cleaner audio with better focus, definition and clarity".

.

Though I agree that artifacts may produce a perceived "better focus, definition and clarity". Depends on the listener.

Which is why I am dismissive of subjective reports most of the time...

Edited by tuga
  • Upvote 1
Link to comment
Share on other sites

1 hour ago, rabski said:

Reflections within a cable will always occcur. The issue is when they can interract and result in reinforcement or cancellation. This is a perfectly well-known phenomenon in high-frequency work and is a major consideration in designing PCBs for higher frequencies.

The extent of any issue affecting digital transmission in 'our' applications is more likely to depend on the robustness of the signal and the ability of the receiver to reject unwanted signals. For the sake of 'it cannot do any harm', I prefer to keep SPDIF cables at multiples of 1.5m, but frankly it's almost certainly unnecessary.

But until those musings are linked to either an observed change in sound quality or a proposal as to how they might affect sound quality then they are just musings with just as likely no impact on the the digital cables in our systems. 
 

The other way of looking at it is to consider just how bad a digital cable has to be before it impacts on the digital signal. I suspect the answer is it has to be very poor indeed to do that. More likely is a badly crimped connected on the plug that causes intermittent contact with clicks and other noises being the result but in between any clicks it probably sounds ok.  
 

The harmful noise I am discussing is generally mentioned as being in the 2 to 5 GHz area, ie well outside the music carrying digital signal. I have yet to see anything that concludes that any half decent digital cable cannot preserve the integrity of the digital signal for the 1m or 2m (or longer) length of cable in normal use.

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...