CD Block Errors, Servos, and the Audible Threshold

[garylkoh]

What is "AVR fluid"?

It's this: http://www.antivibrationmagic.ca/

 

[JackD201]

Hi Don,

Unless I may have made a mistake in the name, but this is the fluid that has been applied to some of the component circuitry by David, and other people that is being referred to as the Blue goo. It is a very expensive material that is applied in a liquid form that hardens and is supposed to lessen vibration and I believe to act as a dampening material.

Rich

Slight correction. The fluid is AVM not AVR. Works well on small signal tubes for damping. It stands up to the heat and if you want to take it off it peels easily.

 

[garylkoh]

I haven't tried to measure the use of AVM on devices, but we coated blank CDR's with it. It reduced block read errors consistently from 7 to 10 down to 5 to 9.

Here's how a AVM is being applied:

View attachment 2066

 

[JackD201]

FIM Super Analog Series? Dimfer gave me a copy of Le Fille and I've had a good listen to the Linda Rondstat. If these two CDs are any indication, it must be a great series. I had no idea the AVM dropped read errors. I just figured the extra weight helped. Winston should make his guys wear masks to avoid blue booger syndrome.

 

[garylkoh]

FIM Super Analog Series? Dimfer gave me a copy of Le Fille and I've had a good listen to the Linda Rondstat. If these two CDs are any indication, it must be a great series. I had no idea the AVM dropped read errors. I just figured the extra weight helped. Winston should make his guys wear masks to avoid blue booger syndrome.

Yeah. I was initially skeptical as well, but also tried other things as well that added weight - stuck sheets of paper, plastic, silicon, carbon fiber, etc. The only thing that consistently reduced the read errors was the AVM. Every little bit helps at the levels that we are working at. You have to remember that the Red Book standard is 220 block read errors per second averaged. We are down to below 10 for Winston's UDCs.

 

[es347]

FIM Super Analog Series? Dimfer gave me a copy of Le Fille and I've had a good listen to the Linda Rondstat. If these two CDs are any indication, it must be a great series. I had no idea the AVM dropped read errors. I just figured the extra weight helped. Winston should make his guys wear masks to avoid blue booger syndrome.

yeah but apparently they are peel off boogers..

 

[MylesBAstor]

Yeah. I was initially skeptical as well, but also tried other things as well that added weight - stuck sheets of paper, plastic, silicon, carbon fiber, etc. The only thing that consistently reduced the read errors was the AVM. Every little bit helps at the levels that we are working at. You have to remember that the Red Book standard is 220 block read errors per second averaged. We are down to below 10 for Winston's UDCs.

That's interesting because some time ago, Bob Ludwig told me the quality of the CD-Rs he was using to send for pressing was not what they were when CD-Rs were first released. He was apalled by the number of reading errors on the newest discs.

 

[DonH50]

I haven't tried to measure the use of AVM on devices, but we coated blank CDR's with it. It reduced block read errors consistently from 7 to 10 down to 5 to 9.

Here's how a AVM is being applied:

View attachment 2066

Interesting, thanks Gary. I have a vague memory about material being applied that reduced reflections (light scattering) on CDs and that improved the error rate. It worsened the wobble (speed variation), but that did not seem to impact the error rate either way. I wonder if that is what is going on? I cannot recall what was used before (it was in the 80's), but it was also a glue-type material. BTW, 10 errors/block seems awfully good to begin with! Isn't the standard something like ten times that? I don't really remember, just that it seemed fairly high'ish.

 

[garylkoh]

That's interesting because some time ago, Bob Ludwig told me the quality of the CD-Rs he was using to send for pressing was not what they were when CD-Rs were first released. He was apalled by the number of reading errors on the newest discs.

Oh, I absolutely believe that. Some of the very best CDR's we could get when I started this re-recording on Black CDRs thing have not been available for 6 years already. When I started this with Winston a few years ago, we were regularly getting below 5 BLER. The plant that made those CDRs stopped making them. These days, it's a challenge getting CD's pressed to the sort of quality demanded of by FIM. That was one of the reasons FIM did not release any new recordings in the past 9 months.

 

[garylkoh]

Interesting, thanks Gary. I have a vague memory about material being applied that reduced reflections (light scattering) on CDs and that improved the error rate. It worsened the wobble (speed variation), but that did not seem to impact the error rate either way. I wonder if that is what is going on? I cannot recall what was used before (it was in the 80's), but it was also a glue-type material. BTW, 10 errors/block seems awfully good to begin with! Isn't the standard something like ten times that? I don't really remember, just that it seemed fairly high'ish.

Yes, 10 BLER/sec is awfully good. The Red Book allows for up to 220, many audiophile CDs are in the range of 35 to 100. BUT you have to remember that these are the correctable C1 errors. So, there will be 1,000,000 scientific types out there who will tell you that I am crazy to tell you that I can hear a difference when the BLER goes down.

In the range of 35 to 100 errors, the wobble doesn't seem to affect the error rate. So, while the AVM coating doesn't help with dynamic balance of the spinning disc, it somehow (we don't know how) reduces the BLER. Since we clear the AVM off the edge of the disc with the Autodesk disc cutter, I don't think that it reduced light scattering either...... and the FIM discs are made with a much thicker of silver/gold so transparency of the reflective coating isn't an issue either.

IMO the FIM UDs sound better, but I can't explain why.

 

[Phelonious Ponk]

Yes, 10 BLER/sec is awfully good. The Red Book allows for up to 220, many audiophile CDs are in the range of 35 to 100. BUT you have to remember that these are the correctable C1 errors. So, there will be 1,000,000 scientific types out there who will tell you that I am crazy to tell you that I can hear a difference when the BLER goes down.

In the range of 35 to 100 errors, the wobble doesn't seem to affect the error rate. So, while the AVM coating doesn't help with dynamic balance of the spinning disc, it somehow (we don't know how) reduces the BLER. Since we clear the AVM off the edge of the disc with the Autodesk disc cutter, I don't think that it reduced light scattering either...... and the FIM discs are made with a much thicker of silver/gold so transparency of the reflective coating isn't an issue either.

IMO the FIM UDs sound better, but I can't explain why.

You're not crazy, Gary, but the odds are pretty high that you're hearing what you expect to hear.

Tim

 

[MylesBAstor]

You're not crazy, Gary, but the odds are pretty high that you're hearing what you expect to hear.

Tim

Actually Tim, one audio group I was associated with did a blind listening test to CDs treated with different accessories some 15 years ago. Jack English, who has his masters in industrial psychology and testing, conducted the listening tests. We uses multiple copies of one Harmonia Mundi disc and listened unknowing to the treated discs. We had unlimited listening time and wrote down our comments which were compiled by Jack. We didn't use an extraordinary system; as I recall it was Vandersteen 3s, Quicksilver 190s and a rather ordinary, though probably modded CD players. And rather ordinary cables. Of the five treatments, only one was selected by everyone as sounding better than the stock disc and that was the Green Pen; the others included rings, adhesive stickers from Harmonix, etc.

Perhaps the most interesting finding though was the internal control that Jack ran on the group. He paired two untreated discs without telling anyone and everyone heard a difference. Not understood then, we now know there were many jitter issues with CD mastering plants back then that lead to these problems.

I detailed these mastering issues in article that appeared in TAS where I had compared different CD releases of a Holly Cole recording mastered by different CD pressing plants. Turned out that Bernie Grundman had sent the same 1640 to all the pressing facilities, yet there were clear differences between as I recall the Canadian and US mastering facilities, with the Canadian sounding far better.

 

[garylkoh]

When I did a lot of these comparisons (before switching exclusively to a music server) I used a Sony ES 5-disc changer. It probably wasn't the best SACD/CD player around, but have someone else load the disc and it's a blind comparison. I wasn't interested in winning any arguments. The only reason I did it was to have the best possible disc for running my demos.

 

[DonH50]

Hey Gary,

I am talking about light scatter from the pits etc. during playback, nothing to do with the edge. I.e. the green pen idea, which I have a tough time believing... Measurements way back when showed nothing changed with or without treating the edge, but treating the surface did marginally, as in barely perceptibly/measurably, improved the received SNR and pulse response. Again, this was ages ago so I do not know if it would be true today.

As for hearing the differences in correctable bit errors, hmmm... I suppose the obvious rejoinder is that if they are properly corrected then nothing is different at the DAC. Something else must be going on, and whilst I could speculate I'd as soon let it drop.

 

[fas42]

The AVM material is viscoelastic, works just like the spring/shock absorber combination of a car's suspension, so it reduces the overall level of vibration of the disc itself and hence in the entire CD spinning mechanism. Weight doesn't do the job, neither does springiness. The key thing is to damp, reduce to a minimum, any physical resonance intruding in any area of the physical reading mechanism. Of course making life easier for the mechanical bits keeps the electrical side of things happier too, because the servos don't have to work as hard trying to keep the laser on track, sucking spikes of current from the power supplies to do their job. Everything affects everything else, everything is important ...

Frank

 

[DonH50]

I understand the basic premise. Unless the material is applied very evenly, something I do not think can be done manually with a sprayer, then the slight weight imbalance caused by imperfect application of the goo (that's a technical term ) will induce periodic speed variations (wobbles). Smaller perturbations may be reduced by the added mass, though I have no idea how large such smaller vibrations may be, nor their impact upon the error rate. That said, reducing the impact of those small wiggles could certainly help.

 

[JackD201]

Are Laser pick ups susceptible to errors from varying distance from laser to reflective surface? CDs are light and stiff. If they are not secured securely could they chatter? Damping and weighting a disc could conceivably keep chatter in the vertical plane down. Chatter could also cause changes in the read angles right?

 

[RBFC]

Are Laser pick ups susceptible to errors from varying distance from laser to reflective surface? CDs are light and stiff. If they are not secured securely could they chatter? Damping and weighting a disc could conceivably keep chatter in the vertical plane down. Chatter could also cause changes in the read angles right?

Many folks might remember the "CD rings" that were applied to the perimeter of the disc. Supposedly, they stabilized the rotation of the disc and reduced the "chatter" in the rotation.

Lee

 

[fas42]

Are Laser pick ups susceptible to errors from varying distance from laser to reflective surface? CDs are light and stiff. If they are not secured securely could they chatter? Damping and weighting a disc could conceivably keep chatter in the vertical plane down. Chatter could also cause changes in the read angles right?

Errors in themselves are not the problem. Remember, in the reading of data from the disk this is all happening in the world of digital, where providing nothing is grossly wrong , everything IS perfect. Would a copy of Excel read of a crappy, badly out of balance old disk behave differently from that stored on an absolutely pristine, perfectly manicured brand new one? No, it would be 100% identical as far as the computer was concerned, and so would the music from the CD be "correct", so long as it remains in digital form!

The big headache is that, finally, at some stage, that digital version has to be turned back to analogue and that's where it all starts to unravel. If the transformation from digital to analogue is not handled absolutely in the best possible way then the sound will be corrupted, distorted. And why is it not done with zero problems? Because there is interference, noise travelling with the signal, through the air, down the mains cables, generated by power supplies, other audio components and other devices entirely.

Making the CD reading operation as "smooth" as possible is just one way of reducing the level of generated interference: one very good reason why music servers straight out of the box can often do a better job than CD players: of course they also introduce another, different can of worms ...

Frank

 

[Phelonious Ponk]

So, Frank, (yes, I read it)...it is all perfect or grossly wrong in the digital realm. It goes awry in the analog realm only, yes? So the earliest point would be the analog output stage of the DAC. Is this any different than any other analog stage in this regard? No? Then it is subject to the same simple principles we apply to everything else, right? Galvanic isolation. Shielding. Power conditioning. The sprinkling of the powdered root of mango, mixed with beaks of virgin turtle doves over RCA connections re-soldered with kosher flux core?

Tim