CD player testing methodology
Based on my experience that the overwhelming % of cases of sonic differences between players is due to E32s and interpolation, I have a few caveats regarding using a CD to evaluate players based on my experience analyzing CD-R recordings:
With few exceptions, the jitter and potential for E32s and interpolation of CD-Rs is FAR worse than that of molded/replicated CDs. This can be overcome by having the finished test CD-R verified by someone with a CD Analyzer such as a AudioDev SA-3, or Datarius CD-4. Once this disc had been verified to be in spec, there is a decent chance for a CD player in new shape to play it without interpolation. If my disc plant was still in operation I'd offer to do the testing, but as it is not...
BUT
The CD system is designed to interpolate due to E32 caused by the sum total of any and all errors in data transfer including the physical characteristics of the disc itself, poorly formatted data on the disc, debris, fingerprints or peanut butter on the disc, dust on the player optics, low player laser output, or issues with any of the servos (focus, tracking, spindle). For the purpose of casual music listening, this is the right strategy. For use as an analytical tool, it is highly flawed. By analogy it is like trying to detect glitches in a waveform using an oscilloscope...but your scope smooths out the waveforms to make them look prettier! The ONE thing which could change this would be the presence of an E32 alert on the player, but I do not know of any currently available players so equipped. HHB used to market a reworked Sony player with one, but that was years ago. I modified several Philips players to output this chip signal to a pulse-stretcher and LED + beeper at work, but at home I don't have one. With an E32 alert you can tell if the player is interpolating and question the sonic attributes at that point.
ALSO
CD recording is (mainly) a CLV (Constant Linear Velocity) operation. This means that the rotational velocity of the disc is stepped down as the pickup follows the pre-groove outwards. Many CD-Recorders characteristics vary proportionally as a result of this lower RPM. This can change the pit-track characteristics, potentially changing jitter and therefore the error rate.
Your strategy is headed in the right direction, unfortunately the CD system was designed to deliver music to masses and not be used as a precision tool to analyze stand-alone players. The situation is different if trying to evaluate PC-based drives, software is available to detect E32s in this environment. Indeed a well made test CD in a PC with a high-end D>A can be used as a precision signal generator if needed.
Cheers,
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Based on my experience that the overwhelming % of cases of sonic differences between players is due to E32s and interpolation, I have a few caveats regarding using a CD to evaluate players based on my experience analyzing CD-R recordings:
With few exceptions, the jitter and potential for E32s and interpolation of CD-Rs is FAR worse than that of molded/replicated CDs. This can be overcome by having the finished test CD-R verified by someone with a CD Analyzer such as a AudioDev SA-3, or Datarius CD-4. Once this disc had been verified to be in spec, there is a decent chance for a CD player in new shape to play it without interpolation. If my disc plant was still in operation I'd offer to do the testing, but as it is not...
BUT
The CD system is designed to interpolate due to E32 caused by the sum total of any and all errors in data transfer including the physical characteristics of the disc itself, poorly formatted data on the disc, debris, fingerprints or peanut butter on the disc, dust on the player optics, low player laser output, or issues with any of the servos (focus, tracking, spindle). For the purpose of casual music listening, this is the right strategy. For use as an analytical tool, it is highly flawed. By analogy it is like trying to detect glitches in a waveform using an oscilloscope...but your scope smooths out the waveforms to make them look prettier! The ONE thing which could change this would be the presence of an E32 alert on the player, but I do not know of any currently available players so equipped. HHB used to market a reworked Sony player with one, but that was years ago. I modified several Philips players to output this chip signal to a pulse-stretcher and LED + beeper at work, but at home I don't have one. With an E32 alert you can tell if the player is interpolating and question the sonic attributes at that point.
ALSO
CD recording is (mainly) a CLV (Constant Linear Velocity) operation. This means that the rotational velocity of the disc is stepped down as the pickup follows the pre-groove outwards. Many CD-Recorders characteristics vary proportionally as a result of this lower RPM. This can change the pit-track characteristics, potentially changing jitter and therefore the error rate.
Your strategy is headed in the right direction, unfortunately the CD system was designed to deliver music to masses and not be used as a precision tool to analyze stand-alone players. The situation is different if trying to evaluate PC-based drives, software is available to detect E32s in this environment. Indeed a well made test CD in a PC with a high-end D>A can be used as a precision signal generator if needed.
Cheers,
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Last edited:
Changes in sound over CD surface
Interestingly enough this discussion has jogged a few memories of events while mastering:
Especially in the 1990s we used to create CDs from analog masters, or 1630 Digital masters which were dubbed from analog masters by the record labels. These digital masters, then, transferred all of the characteristics of the original analog, including tape flutter. I remember one major label which will go nameless which sent a series of 1630 masters to us. We replicated CDs from them, and when the label received the CDs they complained about flutter on the CDs towards the end of the CD. We analyzed the 1630s and the increasing flutter was on them as well, so the problem was not the CD replication process. The problem turned out to be one of the analog decks in their transfer suite which had a misaligned tension servo.
If one had not trouble-shot and verified all of the steps from the original performance through the CD playback, this could be perceived by the end listener as a problem with the CD, indeed even the label QC guy thought it was!
Another old brain cell dump...
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Interestingly enough this discussion has jogged a few memories of events while mastering:
Especially in the 1990s we used to create CDs from analog masters, or 1630 Digital masters which were dubbed from analog masters by the record labels. These digital masters, then, transferred all of the characteristics of the original analog, including tape flutter. I remember one major label which will go nameless which sent a series of 1630 masters to us. We replicated CDs from them, and when the label received the CDs they complained about flutter on the CDs towards the end of the CD. We analyzed the 1630s and the increasing flutter was on them as well, so the problem was not the CD replication process. The problem turned out to be one of the analog decks in their transfer suite which had a misaligned tension servo.
If one had not trouble-shot and verified all of the steps from the original performance through the CD playback, this could be perceived by the end listener as a problem with the CD, indeed even the label QC guy thought it was!
Another old brain cell dump...
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
hhoyt,
I very much appreciate your technical help here. I have never knew until now that a cd player changed the speed to keep the track speed linear, that was something I was wondering when the inside vs outside tracks were being discussed. On a pc based audio system running a music disk is this same phenomena happening that the disk speed is modulated for the different track positions or is that just a constant rotational speed? And how would this work on a software implementation when the information is transferred to ram, is there a modulation from the hdd that is being corrected before going through any D>A conversion or is that just reading the information from a constant speed hdd? Very interesting what you are presenting here, I guess I need to read about all of this in the digital domain and how the information is controlled.
I very much appreciate your technical help here. I have never knew until now that a cd player changed the speed to keep the track speed linear, that was something I was wondering when the inside vs outside tracks were being discussed. On a pc based audio system running a music disk is this same phenomena happening that the disk speed is modulated for the different track positions or is that just a constant rotational speed? And how would this work on a software implementation when the information is transferred to ram, is there a modulation from the hdd that is being corrected before going through any D>A conversion or is that just reading the information from a constant speed hdd? Very interesting what you are presenting here, I guess I need to read about all of this in the digital domain and how the information is controlled.
Most CDP chipsets that I have seen in the past have a E32 flag output pin.
Pretty simple matter to feed that to an led/buzzer alert as you have done.
Most here are probably not aware of this error flag function.
Likely not standard equipment because typical consumer users/listeners would be horrified
!.
Dan.
Pretty simple matter to feed that to an led/buzzer alert as you have done.
Most here are probably not aware of this error flag function.
Likely not standard equipment because typical consumer users/listeners would be horrified
!.Dan.
Last edited:
Most CDP chipsets that I have seen in the past have a E32 flag output pin.
Pretty simple matter to feed that to an led/buzzer alert as you have done.
Most here are probably not aware of this error flag function.
Likely not standard equipment because typical consumer users/listeners would be horrified
Dan.
I brought out the one on an old Phillips, unremarkable. I had to put my finger on a disk to light it up.
PC playback of CD-A
Great question: the spindle servo on any 1x CD player is controlled by the data buffer after the error-correction stage. As the buffer is filled it slows down the spindle speed. If the buffer begins to empty the spindle is commanded to speed up. As far as playing a CD-DA on a PC, the answer depends on the software you are playing the disc with. Earlier versions of Windows Media Player and other players would allow the drive to spin at 4-10x to keep the buffer full. I found the noise of the disc spinning this fast really obnoxious and installed a stand-alone CD player at my PC. These days it is better, both Winamp v5.63 and WMP v12.0.7601.18150 spin the disc at what sounds like 1x, and it is quiet, so the original strategy to keep the buffer full is probably employed.
The interesting aspect of CDs is the original format was CD-DA (Digital Audio). It had a very few extra error-correction bits built-in, since storage space was at a premium. The fix was to use interpolation in an attempt to cover up E32s. The error detection built into the CD system is performed by the chipset in the PC's CD drive. Therefore the interpolation, if any, will be passed along to the PC if the drive is used in CD-DA mode. Once the CD-ROM modes were developed, the drives were built with advanced capabilities which could be applied to the playback of CD-DA discs.
These advanced capabilities are available in some PC drives made after 1995-2000. The can be commanded to read in RAW mode, with error flags streamed on command with some drives. This capability is utilized by the best CD-ripping software (but not by iTunes...I guess they figure the mess is going to be MP3 encoded anyway, so what's a little interpolation between friends?). I use Exact Audio Copy (Exact Audio Copy) which does a great job of watching the player's error flags and letting you know if an E32 was detected. I have compared WAV files pre-CD-DA recording and post EAC rip and found them to be extremely similar to identical in the track data areas. The differences I found are due entirely to framing differences between CD-DA and WAV.
Specifically with regards to your question about HDD to D>A playback of a file, the DA data on the HDD is pulled by the CPU, so the HDD's speed (being constant) affects only the resulting maximum data rate. The overall speed is dependent on internal bus speeds and congestion, but the bandwidth demands of 16-bit 44.1 are low, so there should not be an issue keeping up with real-time playback using a competent D>A. If this is the case, the resulting modulation of timing will be solely dependent on the clock in the D>A.
Buffering and timing of the data to the D>A becomes an issue especially when using older PCs with large 192KHz 24-bit files or 5.1 FLACs. I have heard funny sounds, modulations and noises in these scenarios. The problem can be largely eliminated by the use of higher bandwidth busses to the D>A as well as by using external asynchronous D>As, but that is fodder for another forum, and beyond my expertise.
Cheers,
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Great question: the spindle servo on any 1x CD player is controlled by the data buffer after the error-correction stage. As the buffer is filled it slows down the spindle speed. If the buffer begins to empty the spindle is commanded to speed up. As far as playing a CD-DA on a PC, the answer depends on the software you are playing the disc with. Earlier versions of Windows Media Player and other players would allow the drive to spin at 4-10x to keep the buffer full. I found the noise of the disc spinning this fast really obnoxious and installed a stand-alone CD player at my PC. These days it is better, both Winamp v5.63 and WMP v12.0.7601.18150 spin the disc at what sounds like 1x, and it is quiet, so the original strategy to keep the buffer full is probably employed.
The interesting aspect of CDs is the original format was CD-DA (Digital Audio). It had a very few extra error-correction bits built-in, since storage space was at a premium. The fix was to use interpolation in an attempt to cover up E32s. The error detection built into the CD system is performed by the chipset in the PC's CD drive. Therefore the interpolation, if any, will be passed along to the PC if the drive is used in CD-DA mode. Once the CD-ROM modes were developed, the drives were built with advanced capabilities which could be applied to the playback of CD-DA discs.
These advanced capabilities are available in some PC drives made after 1995-2000. The can be commanded to read in RAW mode, with error flags streamed on command with some drives. This capability is utilized by the best CD-ripping software (but not by iTunes...I guess they figure the mess is going to be MP3 encoded anyway, so what's a little interpolation between friends?). I use Exact Audio Copy (Exact Audio Copy) which does a great job of watching the player's error flags and letting you know if an E32 was detected. I have compared WAV files pre-CD-DA recording and post EAC rip and found them to be extremely similar to identical in the track data areas. The differences I found are due entirely to framing differences between CD-DA and WAV.
Specifically with regards to your question about HDD to D>A playback of a file, the DA data on the HDD is pulled by the CPU, so the HDD's speed (being constant) affects only the resulting maximum data rate. The overall speed is dependent on internal bus speeds and congestion, but the bandwidth demands of 16-bit 44.1 are low, so there should not be an issue keeping up with real-time playback using a competent D>A. If this is the case, the resulting modulation of timing will be solely dependent on the clock in the D>A.
Buffering and timing of the data to the D>A becomes an issue especially when using older PCs with large 192KHz 24-bit files or 5.1 FLACs. I have heard funny sounds, modulations and noises in these scenarios. The problem can be largely eliminated by the use of higher bandwidth busses to the D>A as well as by using external asynchronous D>As, but that is fodder for another forum, and beyond my expertise.
Cheers,
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Last edited:
External E32 annunciator
I believe both of you, but in different contexts: Your average user as referred to by Max abuses CDs and uses Office Depot 100 for $10 CD-Rs on cheap CD recorders, so I would put money on the discs they play having beaucoup E32s and the resulting interpolation. Literally every day I had to show my customers the AudioDev test report's E32 to explain why their CD-R master was rejected.
Scott's experience is that of mine in my optical disc lab environment with discs I had molded. New and well-cared for molded/replicated CDs will have raw BLER in single digits and zero E32s. Indeed our QC procedure rejected any CD-DA jobs which threw an E32, or even those with an E22 averaging more then 5/10s rate. CD-Rs are another story, with as complex a disc/recorder compatibility matrix as the old cassette days. For in-house use I tested hundreds of combinations and settled on the Pioneer DVR/BDR 1xx-2xx series and Taiyo Yuden CD-Rs. In the best examples of this combination single-digit BLER and low jitter could be achieved.
A full jitter analysis is the best judge of playability of a disc, indeed considering the player is trying to reconstruct a train of timing events on harmonically related times or "T"s, every error can be described as a jitter event. CDs are only supposed to contain Ts of 3T to 11T in length, so a chunk of peanut butter will cause a REALLY long "T" which will be considered an out of spec pit or land by a player and trigger error-correction.
Ahhh...ancient technology...I think I recorded a CD-R last year maybe.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Most CDP chipsets that I have seen in the past have a E32 flag output pin.
Pretty simple matter to feed that to an led/buzzer alert as you have done.
Most here are probably not aware of this error flag function.
Likely not standard equipment because typical consumer users/listeners would be horrified
I believe both of you, but in different contexts: Your average user as referred to by Max abuses CDs and uses Office Depot 100 for $10 CD-Rs on cheap CD recorders, so I would put money on the discs they play having beaucoup E32s and the resulting interpolation. Literally every day I had to show my customers the AudioDev test report's E32 to explain why their CD-R master was rejected.
Scott's experience is that of mine in my optical disc lab environment with discs I had molded. New and well-cared for molded/replicated CDs will have raw BLER in single digits and zero E32s. Indeed our QC procedure rejected any CD-DA jobs which threw an E32, or even those with an E22 averaging more then 5/10s rate. CD-Rs are another story, with as complex a disc/recorder compatibility matrix as the old cassette days. For in-house use I tested hundreds of combinations and settled on the Pioneer DVR/BDR 1xx-2xx series and Taiyo Yuden CD-Rs. In the best examples of this combination single-digit BLER and low jitter could be achieved.
A full jitter analysis is the best judge of playability of a disc, indeed considering the player is trying to reconstruct a train of timing events on harmonically related times or "T"s, every error can be described as a jitter event. CDs are only supposed to contain Ts of 3T to 11T in length, so a chunk of peanut butter will cause a REALLY long "T" which will be considered an out of spec pit or land by a player and trigger error-correction.
Ahhh...ancient technology...I think I recorded a CD-R last year maybe.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Thanks for the industrial over view . Would a test disc be found that is up to standard to test the system as to the question originally posed. My test as it where was with tool on hand . A test disc of verified quality would fit the bill much better. Regards
CD-DA Test Disc
There are a number of well replicated test discs on the market, but none I know of which have a track configuration you mentioned: the same track at different positions on the physical disc. A year ago I could have made one for you...
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
There are a number of well replicated test discs on the market, but none I know of which have a track configuration you mentioned: the same track at different positions on the physical disc. A year ago I could have made one for you...
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
The test was for other rather than I. I have a number of the other test discs . The problem is not one that interest me all that much . Thank for your input it is good to have info from people who work with end of the game.
Pono Player
I'm really excited about the Pono Player myself...I listen to discs a lot, but increasingly I listen to files, and I HATE copying files to players/USB memory, etc. when I want the files to go with me. I have been looking for a player with good storage that plays ALL file formats (WAV/FLAC/MP3/OGG/AIFF) as well as all bit-depth and sample rates good enough to use with my home stereo, car system, or portable with headphones. The iPod fails on almost all of these counts. To date there have only been a few players that sounded worth a s#!t: the Astell & Kern (http://www.audioadvisor.com/AstellKern-AK120-Portable-High-Fidelity-System-Package/productinfo/ASK120PKG/#.Ux9Xj2eYYUE), but at $1200 I can't afford it, or another one I can't remember.
The Pono Player looks to be the first affordable player meeting my personal criteria, with audio electronics designed by a member of this forum, Charles Hansen of Ayre Acoustics. I'm really looking forward to the release later this year, and I've already put in an order for one. If he is not contractually bound otherwise, maybe Charles will share the architecture of the new player with us? (hint, hint!!!)
I'm almost as excited that someone is FINALLY firing a volley across the industry trend to smaller, crappier sounding file formats like MP3, whose time has come and gone...storage is dirt cheap these days. Unfortunately it will not go, due to the market penetration of the format. Hey, I grant that for people who music is merely background to their activities, an iPod and MP3s are portable and convenient. But with the Pono player, those of us for who music is front-and-center in our lives will now have a similar device.
(and yes, I'm home sick today...sorry for all the bandwidth!)
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
I'm really excited about the Pono Player myself...I listen to discs a lot, but increasingly I listen to files, and I HATE copying files to players/USB memory, etc. when I want the files to go with me. I have been looking for a player with good storage that plays ALL file formats (WAV/FLAC/MP3/OGG/AIFF) as well as all bit-depth and sample rates good enough to use with my home stereo, car system, or portable with headphones. The iPod fails on almost all of these counts. To date there have only been a few players that sounded worth a s#!t: the Astell & Kern (http://www.audioadvisor.com/AstellKern-AK120-Portable-High-Fidelity-System-Package/productinfo/ASK120PKG/#.Ux9Xj2eYYUE), but at $1200 I can't afford it, or another one I can't remember.
The Pono Player looks to be the first affordable player meeting my personal criteria, with audio electronics designed by a member of this forum, Charles Hansen of Ayre Acoustics. I'm really looking forward to the release later this year, and I've already put in an order for one. If he is not contractually bound otherwise, maybe Charles will share the architecture of the new player with us? (hint, hint!!!)
I'm almost as excited that someone is FINALLY firing a volley across the industry trend to smaller, crappier sounding file formats like MP3, whose time has come and gone...storage is dirt cheap these days. Unfortunately it will not go, due to the market penetration of the format. Hey, I grant that for people who music is merely background to their activities, an iPod and MP3s are portable and convenient. But with the Pono player, those of us for who music is front-and-center in our lives will now have a similar device.
(and yes, I'm home sick today...sorry for all the bandwidth!)
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Actually I am hoping that the use of better file formats will re-energize the music business and the desire for better speakers to play the music at home. Enough with the horrid sounding headphones already, and yes I know there are some good sounding headphones but at over 1K$ minimum I'd rather listen to a good set of speakers.
I see they are getting a lot of negative press. As far as I can tell isn't that the model here? Files copied via computer is the only method.
I am afraid not. I am afraid that budget price, overcompression and no-quality-req is all that is wanted, in average.
Pono
I've read some negative press, and 1/2 have been written by "experts" who poo-pooh anything more elaborate than a basic CD player as an unwarranted expense, the other 1/2 are written my Mac fan boys who view it as an attack on the iEmpire and think the iPod and ALAC are the answer.
To elaborate on my own needs: I want to have the files reside IN the player, not inside fixed devices scattered around my house, car and clothes. As it stands:
I convert FLAC and WAV to MP3 and load USB memory for compatibility with my car,
I play LPs, CDs and networked files of all types at home,
I convert FLAC , WAV and other files to MP3 and load them on a crappy sounding iPod for portable.
That is the file copying I am referring to. My goal is :
To have a single player that sounds good enough to be my main home player, but portable enough to bring to my car or wear portable.
The player must play all the file types, bit-depths and sampling rates I own without conversion to MP3.
I want to be able to transfer from my networked storage to the device once to use wherever I want elsewhere.
Reasonable price, unlike the Astell & Kern.
The Pono Player seems to fit the bill.
As far as the aspect of the Pono Project which is bringing HD files to consumers, I think that is a much more problematic sell, as many have stated here, the public in general is deaf and/or music isn't that important to them, so crappy MP3s are good enough. I just hope there is sufficient success to keep the HD channel open, but time will tell.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
I've read some negative press, and 1/2 have been written by "experts" who poo-pooh anything more elaborate than a basic CD player as an unwarranted expense, the other 1/2 are written my Mac fan boys who view it as an attack on the iEmpire and think the iPod and ALAC are the answer.
To elaborate on my own needs: I want to have the files reside IN the player, not inside fixed devices scattered around my house, car and clothes. As it stands:
I convert FLAC and WAV to MP3 and load USB memory for compatibility with my car,
I play LPs, CDs and networked files of all types at home,
I convert FLAC , WAV and other files to MP3 and load them on a crappy sounding iPod for portable.
That is the file copying I am referring to. My goal is :
To have a single player that sounds good enough to be my main home player, but portable enough to bring to my car or wear portable.
The player must play all the file types, bit-depths and sampling rates I own without conversion to MP3.
I want to be able to transfer from my networked storage to the device once to use wherever I want elsewhere.
Reasonable price, unlike the Astell & Kern.
The Pono Player seems to fit the bill.
As far as the aspect of the Pono Project which is bringing HD files to consumers, I think that is a much more problematic sell, as many have stated here, the public in general is deaf and/or music isn't that important to them, so crappy MP3s are good enough. I just hope there is sufficient success to keep the HD channel open, but time will tell.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Howie, this one cost onnly half, similar specs/functionality: Amazon.com: Colorfly Pocket HiFi C4 16G Pro Media Player 24bit 192kHz MP3 AMP Hi-Fi DAC: MP3 Players & Accessories
Jan
Yeah, and that's the thing. It's as if the Pono bunch are totally oblivious to what's been going on already in the high end headphone market.
se
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