Hunt for RFI offenders

[sandyk]

18 minutes ago, Spacehound said:

Anyway, "appeals to authority", of which you seem so fond, are a logical fallacy because they  prove nothing either way.

 

As for your summing up of the knowledge and abilities of the 3 people linked to, I would say that they almost certainly have far more expertise , and are far more up to date than you are in this area !

 

 

[One and a half]

2 hours ago, Spacehound said:

While I agree about it being analogue, it's a representation, as you say. It's not somethin that you have to amplify or whatever accurately.

Silberman is only a snake oil cable  manufacturer so I take no notice of him. As for  the others, Rankin talks  pure bollox at times. Swenson  is better but I think he is mistaken on some things.

 

Anyway, "appeals to authority", of which you seem so fond, are a logical fallacy because they  prove nothing either way.

 

 

So are these references worthless?

 

Footnote 1
For those who are truly interested in diving in deeper...

High Speed Digital Design: A Handbook of Black Magic
Howard Johnson, Martin Graham, 1993

High Speed Signal Propagation: Advanced Black Magic
Howard Johnson, 2003

Electromagnetic Compatibility Engineering
Henry W. Ott, 2009

EMC for Product Designers, Fourth Edition
Tim Williams, 2007

Grounding and Shielding: Circuits and Interference
Ralph Morrison, 2007

Digital Circuit Boards: Mach 1 GHz
Ralph Morrison, 2012

Solving Interference Problems in Electronics
Ralph Morrison, 1995

Noise and Other Interfering Signals
Ralph Morrison, 1991

Read more at https://www.audiostream.com/content/theres-no-such-thing-digital-conversation-charles-hansen-gordon-rankin-and-steve-silberman-p#RSUrc61YKh1Tmc9z.99

[mansr]

5 hours ago, sandyk said:

What is exported from the USB Port to the DAC is an ANALOGUE  representation of the digital data

In a USB signal, a voltage transition during a bit interval signifies a zero, lack of transition signifies a one (NRZI code). There either is or isn't a transition. Very binary.

[motberg]

FWIW.. I have a TriField meter.. from memory, worst offenders in my room are the LPS´s, I wrap these with a few layers of Mumetal if they are close to anything I think may be sensitive. However iirc 18 CM distance = 2 layers of 1.5mm Mumetal. Also 1 large sheet Mumetal =$25 USD .. so....

 

I have a strange situation on the analog side... I think it is related to tube gear only.. if I have a tube preamp connected with non-shielded XLR or RCA cables, I get an intermittent audible whistle at 7.5kz (similar sound to what I think I hear sometimes from a computer monitor). If I use balanced shielded cables, then this whistle seems to be reduced to near inaudibility or eliminated. I am not sure if it is the tube preamps, but seems to not happen with SS preamps... I have tried trouble shooting the exact source with no success. I think I had the same problem with 4 different tube preamps, though again, not sure if that is the source due to the intermittent nature of the whistle makes it difficult to positively identify (not only that, is that I think during troubleshooting I start to hear the whistle and I am not sure if it is really present.. the frequency seems similar to what is described as tinnitus..).

 

I was thinking it should be pretty easy to test RFI effects by introducing the offensive stuff into the system and record silence into a DAW equipped battery laptop, but haven't yet sketched out the test procedures or checked the noise floor of a typical laptop mic input (could always use a home studio USB ADC I guess). That way, no need rely on hearing sensitivity, transducer accuracy or eliminating masking during music playback.

[Spacehound]

4 hours ago, One and a half said:

So are these references worthless?

 

Footnote 1
For those who are truly interested in diving in deeper...

High Speed Digital Design: A Handbook of Black Magic
Howard Johnson, Martin Graham, 1993

High Speed Signal Propagation: Advanced Black Magic
Howard Johnson, 2003

Electromagnetic Compatibility Engineering
Henry W. Ott, 2009

EMC for Product Designers, Fourth Edition
Tim Williams, 2007

Grounding and Shielding: Circuits and Interference
Ralph Morrison, 2007

Digital Circuit Boards: Mach 1 GHz
Ralph Morrison, 2012

Solving Interference Problems in Electronics
Ralph Morrison, 1995

Noise and Other Interfering Signals
Ralph Morrison, 1991

Read more at https://www.audiostream.com/content/theres-no-such-thing-digital-conversation-charles-hansen-gordon-rankin-and-steve-silberman-p#RSUrc61YKh1Tmc9z.99

Not at all. The 'analog' books are fine, from what I can see from the Amazon 'blurb'.

 

But the two 'black magic' books  with their calling 'high speed digital design' being from  10 Mhz up have an extremely low concept of the bottom end of high speed. But they might be useful, our  data rates are pretty slow.

 

One part I did note is where analog and digital circuits meet.  Which of course applies very much to our stuff (as your binary/decimal to voltage chart showed yesterday). That of course is in a DAC.

 

But in our stuff  it isn't anywhere else. 

 

And that's why I think these  USB 'improvement' devices and similar gadgets are a complete waste of money. As  is most of this stuff (maybe all of it) INSIDE the computer, such as using SSD's rather than disks..  And I include these software 'optimizers' in that.

 

Internally generated RFI. Don't use a 'chip' converter. It is impossible to separate the noisy digital  part from the output as they are too close together, the 'active' part of the chip  is probably only about 1/8 to 1/4  inch square.

 

Protect the DAC and amplifier from externally generated RFI. This must be part of their design of course, unless you want to shield each box in a faraday cage. Don't bother about the computer, it generates so much itself that it won't notice outside influences. 

 

And of course follow the ages old 'good electronic practice'. That can never do any harm, even if in some boxes it won't give much, if any,  benefit.

[Spacehound]

9 hours ago, fas42 said:

 

Possibly misreading ... I'm talking about any system that relies on the music source being stored in digital form - that data, while being considered as bits, is always fine - as you say. The troubles arise in the conversion to analogue, and anywhere from that point on. Those systems which are full analogue - tape, vinyl, etc - seem more immune to the particularly pernicious interference issues - hence, people talk of getting "analogue sound" ...

 

Further to that, I have a CDP here which is extremely flaky in pulling off CDR material - it struggles, the sound glitches like crazy at times, as the error recovery and interpolation circuitry does its best - but, it still manages to read the disk. So, the data integrity there is badly 'degraded', corrupted, from the interpolation - yet the music still comes through with full tonality ... I have no problems with even severe digital corruption, in terms of getting good sound.

"The troubles arise in the conversion to analogue"

 

Exactly. That's where it all matters. The analogue stuff  afterwards  has been fully understood for a very long time and is largely  'non-controversial'.

 

The digital part in front should not  be controversial either. But there are two problems that make it so.

 

1) There are many who don't actually know how computers work, so they figure out how they MIGHT work. And then try to 'solve' the problems their incorrect  'method' causes. 

They don't understand that  the design, which is not as they think,  was all figured out in the 1940's to AVOID those problems before anyone even picked up a soldering iron and got stuck in. Or it would never have worked at all. And the basic  principles have not changed since. (But they probably soon will so keep paying attention  )

 

2) There are some firmly stuck in an 'analogue' paradigm and refuse point blank to come out of it. 

[adamdea]

2 hours ago, mansr said:

In a USB signal, a voltage transition during a bit interval signifies a zero, lack of transition signifies a one (NRZI code). There either is or isn't a transition. Very binary.

Digital and analogue are terms which describe the way in which information is coded not the medium in which it is transmitted or stored. Describing the medium as analogue is a category error. Like many category errors and basic misuses of terminology which afflict audio writing, it  is not a matter of pedantic nicety: there is a foolish thing which people like to say because it sounds as though it means something.

It is quite difficult to say the thing which SandyK wishes to say without getting it wrong. This number 1 is a piece of digital information. It can be written on a piece of paper using a continuous line of graphite approximating to a straight line. Does that mean the 1 is really an analogue piece of information ? Does it mean that deviations in the line of graphite from absolute rectilinearity are material to its interpretation? Does it become 0.9998 if you photocopy it 50 times?   

There is no such thing as an analogue representation of a digital signal; it does not mean anything and no meaningful thought can proceed from it. The nearest I can get to a way of saying it is- the digital data is encoded in a medium which looks quite similar to an analogue signal. The beauty of the attempt to put it clearly is that it conjures its own answer (so what?) out of thin air. 

[Speedskater]

7 hours ago, One and a half said:

Footnote 1
For those who are truly interested in diving in deeper...

This is an excellent list of experts. Lets add Keith Armstrong to the list:

Keith Armstrong

I see that his papers have been moved from his consulting company.

 January 2018: All of the free material that was available here, and much more,
is now available for free from emcstandards.co.uk. 

https://www.emcstandards.co.uk/

https://www.emcstandards.co.uk/sitemap

[sandyk]

8 hours ago, mansr said:

In a USB signal, a voltage transition during a bit interval signifies a zero, lack of transition signifies a one (NRZI code). There either is or isn't a transition. Very binary.

 

It is no longer a case of the "  DAC receives a bright shiny string of brand new bits." and requires further processing, just as the stored binary waveforms on a HDD do.

If the Signal Integrity of the data received at the USB input of the DAC is so bloody good, why do so many members need to use USB widgets,  cleaner USB PSUs,  and higher quality USB cables with improved isolation between the Data and power leads to obtain half decent USB audio, with many STILL reporting that a good quality CD player still sounds better to them , despite the PC having the advantage of reading from System Memory ?

 

Perhaps you need to have a good read of the information in the links that one and a half and myself have provided too ???

[Ralf11]

a real sloppy 1 could be read as a 7

 

 

I'd love to expound on errors & their correction but I have to go get my telomeres rewrapped right now

[fas42]

1 hour ago, sandyk said:

 

If the Signal Integrity of the data received at the USB input of the DAC is so bloody good, why do so many members need to use USB widgets,  cleaner USB PSUs,  and higher quality USB cables with improved isolation between the Data and power leads to obtain half decent USB audio, with many STILL reporting that a good quality CD player still sounds better to them , despite the PC having the advantage of reading from System Memory ?

 

Because, there is not "perfect" isolation between the workings on the digital side, from that on the analogue side - just because you've added in some of the usual bits and pieces to make it so, doesn't actually guarantee that you've reached 100% success. And in my experience 99.9% success still ain't good enough, so to speak ... the slightest breakthrough of noise from the digital side, via any coupling mechanism, will be audible - only scrupulous attention to every last detail will excise all the noise demons - the sloppiness of implementation and setup one can get away with in analogue source rigs ain't good enough for digital.

 

The plus side is that digital playback, if clean enough, is absolutely amazing - but that won't happen if the efforts aren't made.

[Don Hills]

1 hour ago, sandyk said:

(...) If the Signal Integrity of the data received at the USB input of the DAC is so bloody good, why do so many members need to use (...) widgets (...)  to obtain half decent USB audio (...)

 

In some cases, it's simply because they believe the widgets help. In others, it's because their DACs are poorly designed. Affordable DACs exist where the perturbation of the output by "unclean" input is so low as to be down in the DAC's self noise.

[sandyk]

1 hour ago, Ralf11 said:

a real sloppy 1 could be read as a 7

 

 

I'd love to expound on errors & their correction but I have to go get my telomeres rewrapped right now

 

 Sorry Mr. Anti Audiophile, but nobody has claimed that Data errors arise from mediocre USB implementation,

so you can go back into your kennel and lay in wait for the Postman.

 There are however many reports about noise via the USB cable affecting generic USB DAC inputs, resulting in lacklustre performance.

[sandyk]

29 minutes ago, Don Hills said:

 

In some cases, it's simply because they believe the widgets help. In others, it's because their DACs are poorly designed. Affordable DACs exist where the perturbation of the output by "unclean" input is so low as to be down in the DAC's self noise.

 

 Come on Don, it's about time you guys stopped portraying so many C.A. members as either gullible or stupid !

Some of you seem to think you are infallible in this area , but it's the Consumer who compares your design's performance AND reliability, with designs from other companies, and helps decide whether you keep your job or are made redundant.

[mansr]

13 minutes ago, sandyk said:

it's about time you guys stopped portraying so many C.A. members as either gullible or stupid !

As soon as they stop being those things.

[fas42]

1 hour ago, sandyk said:

 

 Come on Don, it's about time you guys stopped portraying so many C.A. members as either gullible or stupid !

 

People who are sensitive to the audible issues that impact here can certainly hear the variation when various things are tried - their difficulty is more likely to be in the area of determining which variation is closer to eliminating the key anomalies; IOW, which is the "most accurate". Unless one has heard extremely clean reproduction of a particular track, and thus has a reference to go by, one can easily be led astray in thinking that they're getting "better" quality when in fact that is not the case.

[Ralf11]

1 hour ago, sandyk said:

 

 Sorry Mr. Anti Audiophile, but nobody has claimed that Data errors arise from mediocre USB implementation,

so you can go back into your kennel and lay in wait for the Postman.

 

 

 

you are barking up the wrong tree scruffy

[One and a half]

16 hours ago, motberg said:

FWIW.. I have a TriField meter.. from memory, worst offenders in my room are the LPS´s, I wrap these with a few layers of Mumetal if they are close to anything I think may be sensitive. However iirc 18 CM distance = 2 layers of 1.5mm Mumetal. Also 1 large sheet Mumetal =$25 USD .. so....

 

I have a strange situation on the analog side... I think it is related to tube gear only.. if I have a tube preamp connected with non-shielded XLR or RCA cables, I get an intermittent audible whistle at 7.5kz (similar sound to what I think I hear sometimes from a computer monitor). If I use balanced shielded cables, then this whistle seems to be reduced to near inaudibility or eliminated. I am not sure if it is the tube preamps, but seems to not happen with SS preamps... I have tried trouble shooting the exact source with no success. I think I had the same problem with 4 different tube preamps, though again, not sure if that is the source due to the intermittent nature of the whistle makes it difficult to positively identify (not only that, is that I think during troubleshooting I start to hear the whistle and I am not sure if it is really present.. the frequency seems similar to what is described as tinnitus..).

 

I was thinking it should be pretty easy to test RFI effects by introducing the offensive stuff into the system and record silence into a DAW equipped battery laptop, but haven't yet sketched out the test procedures or checked the noise floor of a typical laptop mic input (could always use a home studio USB ADC I guess). That way, no need rely on hearing sensitivity, transducer accuracy or eliminating masking during music playback.

This is an interesting problem you have and out of this thread but related. Could you copy the contents and start a new thread? You would obtain better focus and outcome. 

[Spacehound]

10 hours ago, sandyk said:

 

It is no longer a case of the "  DAC receives a bright shiny string of brand new bits." and requires further processing, just as the stored binary waveforms on a HDD do.

If the Signal Integrity of the data received at the USB input of the DAC is so bloody good, why do so many members need to use USB widgets,  cleaner USB PSUs,  and higher quality USB cables with improved isolation between the Data and power leads to obtain half decent USB audio, with many STILL reporting that a good quality CD player still sounds better to them , despite the PC having the advantage of reading from System Memory ?

 

Perhaps you need to have a good read of the information in the links that one and a half and myself have provided too ???

"so many members"

 

With 100,000 plus 'members' and only a tiny number ever posting anything whatsoever you can  have no idea  what  percentage  of us use or even consider these gadgets.

 

Or know what percentage of us think  CD players sound "better".

 

And the received bits are not "further processed" they are read and bright shiny new ones are sent on.

Also as Mansr pointed out, and which you chose to ignore,  it's all about 'transitions' (and I will add that  the 'value' of the 'crossing point' is not at all critical).

[Spacehound]

That's inside the computer. This is what the USB port sends to the DAC.

Note that as it depends on transitions both one and zero can have an 'analogue value'  of either  a positive or negative voltage. Also the voltages   can wobble about a lot as neither the zero  high, or low are at all critical.

 

[sandyk]

23 minutes ago, Spacehound said:

And the received bits are not "further processed" they are read and bright shiny new ones are sent on.

Also as Mansr pointed out, and which you chose to ignore,  it's all about 'transitions' (and I will add that  the 'value' of the 'crossing point' is not at all critical).

 

Since when have differential receivers been perfect, and also able to ignore all noise riding along with the Data ?

 USB is no better in that respect than Coax SPDIF where typically a Schmidt trigger regenerates the waveform at hopefully the correct point of the incoming waveform to avoid Jitter.

 Since when has mansr been any better informed about the USB area than you are?

 You are both out of touch with recent developments in this area, and ignore the contents of the links posted because you both think you know better than the authors of those reports,  despite not being actively involved in investigations in this area !

 

[sandyk]

17 minutes ago, Spacehound said:

That's inside the computer. This is what the USB port sends to the DAC.

 

 

So what ???

 That waveform is nowhere near as perfect when received at the USB input of the DAC via a USB cable that may be more than a couple of metres long. There is also noise riding along with the analogue representation of the digital data. 

Have you ever looked at the D+ and D- leads at the DAC end with a CRO ?  (I have.)  You will even see low level binary data on the +5V wire in the REAL world . 

[Spacehound]

20 minutes ago, sandyk said:

So what ???

 That waveform is nowhere near as perfect when received at the USB input of the DAC via a USB cable that may be more than a couple of metres long. There is also noise riding along with the analogue representation of the digital data. 

Have you ever looked at the D+ and D- leads at the DAC end with a CRO ?   You will even see low level binary data on the +5V wire in the REAL world . 

It doesn't have to  be 'perfect' or even close. That's  the whole point. This stuff was all figured out before they built the first 'Colossus'  in 1943 or it wouldn't have worked.

 

As for your previous post:

 

You hold up  as a 'master'  anyone who agrees with you and dismiss, sometimes even insult, everyone that doesnt.

 

I can't speak for mansr (who knows far more than me about most things), but I am as 'up to date' as so far physically  exists, on computing stuff you probably can't even comprehend.  I'm actually doing it though supposed to be retired - they asked for me back, but I'm not doing it full time. Here's a picture:

 

Anyway it's all way of topic and I don't want to upset one and a half.

 

 

[Spacehound]

Just now, Spacehound said:

 

 

 

sorry, double post.

[sandyk]

1 hour ago, Spacehound said:

"so many members"

 

With 100,000 plus 'members' and only a tiny number ever posting anything whatsoever you can  have no idea  what  percentage  of us use or even consider these gadgets.

 

Or know what percentage of us think  CD players sound "better".

 

And the received bits are not "further processed" they are read and bright shiny new ones are sent on.

Also as Mansr pointed out, and which you chose to ignore,  it's all about 'transitions' (and I will add that  the 'value' of the 'crossing point' is not at all critical).

 

The attached is more like what is received at the DAC !

From :  https://www.rs-online.com/designspark/raspberry-pi-waveforms