- Sony CDP101 repair - 21 Updates
- Why CD laser unit fails so often? - 4 Updates
| dplatt@coop.radagast.org (Dave Platt): May 31 11:13AM -0700 In article <a4021516-0195-49a3-8685-b446a78020ab@googlegroups.com>, >out of phase/polarity at some >point in the chain inside the >player? As I recall: in some CD players (mostly very old ones?), there's only a single DAC, which is shared between the two channels. The "left" and "right" samples are converted back to analog at slightly different times, in alternating sequence. The analog voltage coming out from the DAC is then fed to a pair of sample-and-hold circuits, one per channel, and these then feed the (low-pass) analog reconstruction filters. As a result of this, there's a slight phase delay (equal to the actual DAC conversion time, or half of the nominal sample rate for the stereo signal) introduced between the two channels. This would tend to "pull" the perceived stereo image slightly to one side, since our ear/brain systems are sensitive to a signal's inter-aural arrival times as well as to inter-aural amplitude differences. [I used this trick years ago as a way of enabling a videogame system to convert a monaural sound sample to one which appeared to move left and right, quite smoothly - a simple DSP algorithm did both sample interpolation and filtering, to create timing and amplitude and frequency-response differences between two copies of the sampled sound. It could even introduce the equivalent of Doppler shift, to mimic a sound source moving towards or away from the listener. My first patent ever!] It sounds as of the CDP101 used a "tweaked" reconstruction filter, to introduce a bit of phase difference between the analog signals that would partially cancel out the phase difference introduced by the use of the single DAC. I don't think I've seen the "one DAC, two sample-and-hold" technique used in a CD or similar media player in a lot of years. Stereo (or even 5-channel) DACs are jellybean parts these days. |
| dplatt@coop.radagast.org (Dave Platt): May 31 11:18AM -0700 In article <67e9586e-848b-4a98-8095-cae6430fec09@googlegroups.com>, >The next week he came in with the CD, and I >compared it to the copy in my inventory: His was >a REMASTER.... And, some remasters are dreadful. Not infrequently the remastering engineer has been of the "louder is better" school, and the remastered disc suffers from serious signal compression and (more than occasionally) actual clipping. The dynamic range of the remaster is often poorer than that of the original CD. The spectral balance will also often be "played with". |
| Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au>: Jun 01 04:37AM +1000 > out of phase/polarity at some > point in the chain inside the > player? **It did with the CDP-101, because only one DAC was used and shared between left and right channels. All (?) other players used two DACs (one for each channel) and the delay was not required. For the record, I just checked the schematic of the 701. The 701 used two DACs. One for each channel. It does not use a delay on one OP amp. Both OP amp feedback resistors are 15k, paralleled by a 75pF cap. This likely contributes to the difference in sound quality noted by many listeners (including me). -- Trevor Wilson www.rageaudio.com.au |
| Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au>: Jun 01 04:43AM +1000 On 1/06/2017 4:18 AM, Dave Platt wrote: > occasionally) actual clipping. The dynamic range of the remaster is > often poorer than that of the original CD. > The spectral balance will also often be "played with". **Indeed. That little trick was used by Mobile Fidelity back in the early 1980s. I found some of their limited edition, heavy duty, virgin vinyl, very expensive LPs, unlistenable. I recall the damage MF did to my favourite female artist - Crystal Gayle, on her seminal LP, Don't It Make My Brown Eyes Blue. The bog-standard LP was a glorious thing. The MF was something else entirely and a good deal more expensive too. I never purchased another MF product. Well, except my UHQR Pink Floyd - Dark Side Of The Moon. It is still unopened and the last figure I saw was about US$1,500.00. A nice return on my 25 Bucks. -- Trevor Wilson www.rageaudio.com.au |
| bitrex <bitrex@de.lete.earthlink.net>: May 31 05:12PM -0400 On 05/30/2017 02:54 AM, Phil Allison wrote: > I reckon there must have been a bit of dead cocky on the lens. > .... Phil It would look great with my Onkyo TX-2500 mk II receiver in my "retro stereo corner." Give ya one fiddy for it. |
| amdx <nojunk@knology.net>: May 31 04:50PM -0500 On 5/30/2017 1:54 AM, Phil Allison wrote: > I reckon there must have been a bit of dead cocky on the lens. > .... Phil I still have a Magnavox (NAP) FD 1040 that I bought in 1984, not quite as old as yours. I used it for years and then it quit working, I couldn't locate the problem. I worked for an NAP authorized service center at the time and even calling tech support didn't lead to a repair. So I sent it to the NAP factory service center for repair. They had it for well over a month and returned it saying they could not fix the problem. I mentioned the situation to one of our other techs, he said, "let me take a look at it" he put a wire through all the vias and resoldered them. He gave me back a working CD Player! Mikek |
| jurb6006@gmail.com: May 31 03:33PM -0700 >"Is there something I don't know about CD players" As been pointed out, the channels are read sequentially. There are a few things most people don't know about CDs. First of all that they could be quadrophonic. It was never involved, no quad CDs were made and no quad CD players were made. Also the digital compression scheme used was necessary to make the CD small enough to facilitate in dash CD players in cars of the time, which generally had a predetermined space for the stereo. (that is also why they are not 48 KHz)This facilitated aftermarket stereos and has been changed in more recent cars. The strive to make it non standard so that they have a captive market on the stereos. And the LASER beam is not a beam at all, it is conical shape. this means that on the bottom surface of the CD where all the scratches and dirt are, the pickup of the signal does not depend on a teeny tiny area. On a stamped CD, the pits are not darkened at all. They cancel the light out by being ¼ wavelength of light deeper. There is no mask nor pigment involved, unlike burned CDs. In the beginning of stamping CDs in the US, Teelarc could not produce a defect free disk. They had to get engineers from overseas to figure out what they were doing wrong. So much for "America number one ?". All obsolete. Now DVDs are obsolete. Now bluray is obsolete. They got a holographic disk now that holds so much more data that nobody can use it. Thatis the only reason it is not on shelves. Also, do you really want your entire library of movies and whatever on one disk ? Scratch that. |
| Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au>: Jun 01 08:45AM +1000 On 1/06/2017 4:43 AM, Trevor Wilson wrote: > never purchased another MF product. Well, except my UHQR Pink Floyd - > Dark Side Of The Moon. It is still unopened and the last figure I saw > was about US$1,500.00. A nice return on my 25 Bucks. **Scratch that. Looks like my DSOTM UHQR LP is now worth a little North of 2 Grand. Gotta be happy with that. Factory sealed, still has the guarantee label stuck to it. -- Trevor Wilson www.rageaudio.com.au |
| thekmanrocks@gmail.com: May 31 04:05PM -0700 Trevor Wilson wrote: "**It did with the CDP-101, because only one DAC was used and shared between left and right channels. All (?) other players used two DACs (one for each channel) and the delay was not required. For the record, I just checked the schematic of the 701. The 701 used two DACs. One for each channel. It does not use a delay on one OP amp. Both OP amp feedback resistors are 15k, paralleled by a 75pF cap. This likely contributes to the difference in sound quality noted by many listeners (including me). -- Trevor Wilson www.rageaudio.com.au " Thanks, Trevor W, for that cogent explanation, and for not cowing to the sudden dip in S/N ratio in this thread. |
| thekmanrocks@gmail.com: May 31 04:14PM -0700 jurb wrote: "As been pointed out, the channels are read sequentially. " On early machines such as the CDP101. Trevor did mention that subsequent models began incorporating DACs for each channel. Something I am aware of that you didn't bring up: Pre-emp/De-emp. Some CDs were mastered with a rising high- end frequency response, and a corresponding attenuation in the player. Sort of a "Dolby NR" for CDs I guess? Nothing I ripped even in EAC flags the pre-emp, even though the vast majority of my CD collection are from the era when pre-emphasis was most likely to be used. I would have to load the WAVs ripped from every CD in my collection into a DAW and run a spectro on it to see if it looked unusually top- heavy, suggesting emphasis. Can't always tell by ear. |
| etpm@whidbey.com: May 31 04:49PM -0700 On Wed, 31 May 2017 11:18:36 -0700, dplatt@coop.radagast.org (Dave Platt) wrote: >occasionally) actual clipping. The dynamic range of the remaster is >often poorer than that of the original CD. >The spectral balance will also often be "played with". Years ago when Pink Floyd's Dark Side Of The Moon came out on CD I bought a copy and was amazed at how much better it sounded than the vinyl. Then Happy Trails by Quicksilver Messenger Service came out on CD and I was anticipating a much better sounding copy. Nope. It sounded just as bad as my vinyl and reel to reel copies. I guess the master tapes done by Pink Floyd were much better than the ones that held Quicksilver's music. Eric |
| thekmanrocks@gmail.com: May 31 05:02PM -0700 Dave Platt wrote: "And, some remasters are dreadful. Not infrequently the remastering engineer has been of the "louder is better" school, and the remastered disc suffers from serious signal compression and (more than occasionally) actual clipping. The dynamic range of the remaster is often poorer than that of the original CD. The spectral balance will also often be "played with". " As was the case with this customer's version of the Wonder CD I was playing in the store. Needless to say, I convinced him to buy the unremastered orignal! |
| Michael Black <et472@ncf.ca>: May 31 08:28PM -0400 |
| Phil Allison <pallison49@gmail.com>: May 31 05:29PM -0700 Dave Platt wrote: ----------------- > "pull" the perceived stereo image slightly to one side, since our > ear/brain systems are sensitive to a signal's inter-aural arrival > times as well as to inter-aural amplitude differences. ** You need to apply some common sense before making such conclusions. What does such a tiny delay amount to in distance ? Answer: your head being offset by 1.7mm from exact centre of a pair of speakers. You are employing the worst of audiophool non-think which holds that IF it exists it MUST be audible. Bollocks. .... Phil |
| Phil Allison <pallison49@gmail.com>: May 31 05:32PM -0700 Trevor Wilson wrote: -------------------- > feedback resistors are 15k, paralleled by a 75pF cap. This likely > contributes to the difference in sound quality noted by many listeners > (including me). ** More TW audiophool nonsense. There is no audible difference and the 15k resistor business is an obvious red herring. Just do a tiny bit of math on those numbers. ..... Phil |
| Phil Allison <pallison49@gmail.com>: May 31 05:35PM -0700 amdx wrote: ------------- > me take a look at it" he put a wire through all the > vias and resoldered them. > He gave me back a working CD Player! ** That is a nasty and pretty rare fault. I've had to do the same only twice ever. Few techs would even think of it. .... Phil |
| Phil Allison <pallison49@gmail.com>: May 31 05:37PM -0700 thekma...@gmail.com wrote: -------------------------- > www.rageaudio.com.au " > Thanks, Trevor W, for that cogent > explanation, ** ROTFL !! TW is spewing his usual audiophool nonsense while a know nothing idiot is lapping it up. ..... Phil |
| Clifford Heath <no.spam@please.net>: Jun 01 10:14AM +1000 On 01/06/17 10:37, Phil Allison wrote: >> explanation, > ** ROTFL !! > TW is spewing his usual audiophool nonsense while a know nothing idiot is lapping it up. Maybe. Interesting related story: I built a stereo sonar, using a 40KHz transmitter with two receivers 5cm each side. The aim was to resolve the angle of the response echo. Because the receiver circuits detected a response passing a threshold, and because the receivers would be still resonating from the transmit pulse, the echo could arrive either in or out of phase, so the threshold was passed a cycle earlier or later. 40KHz acoustic wavelength is 7mm, so there was a 10 degree sawtooth uncertainty in the angle of the received signal. A time delay of one cycle is 25us. The only way around this is to not use thresholding, but to digitize each receiver's waveform and compute the departure from normal ring-down caused by a reflected signal. Since our ears use relative phase to locate signals, I'd think that a high frequency phase shift (at say 4KHz) would very likely affect the stereo imaging. Clifford Heath. |
| Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au>: Jun 01 10:50AM +1000 On 1/06/2017 10:32 AM, Phil Allison wrote: > ** More TW audiophool nonsense. > There is no audible difference and the 15k resistor business is an obvious red herring. > Just do a tiny bit of math on those numbers. **If there is no audible difference, why did Sony use different value resistors in the 101 and the same values in the 701? I presume you are suggesting that there is a measurable difference, but that difference is inaudible? -- Trevor Wilson www.rageaudio.com.au |
| Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au>: Jun 01 10:53AM +1000 On 1/06/2017 10:35 AM, Phil Allison wrote: > I've had to do the same only twice ever. > Few techs would even think of it. > .... Phil **Not really. The Magnavox was identical the early Philips/Marantz units and was built in Belgium. Those whacky Belgians could have learned a great deal from Sony about how to make decent PCBs. The lasers were great, but the PCBs were poorly assembled. -- Trevor Wilson www.rageaudio.com.au |
| etpm@whidbey.com: May 31 06:15PM -0700 On Wed, 31 May 2017 20:28:14 -0400, Michael Black <et472@ncf.ca> wrote: >new medium. I don't know whether it applies here, I have the record, but >don't have it on CD. > Michael All my recordings of Happy trails were obviously made from the same master tapes. I can hear the exact same noise in the same places on them all. In fact, the CD almost sounds like it was recorded from the LP I have. I saw Quicksilver live in San Jose way back when. It was a great venue and a great concert. And I was listening to Who Do You Love just a couple days ago which made me think of the difference in the quality of the recordings. Eric |
| "pfjw@aol.com" <pfjw@aol.com>: May 31 11:22AM -0700 On Wednesday, May 31, 2017 at 12:34:50 PM UTC-4, Miguel Giménez wrote: May be a focus problem unrelated to laser? Likely. Peter Wieck Melrose Park, PA |
| Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au>: Jun 01 04:50AM +1000 On 31/05/2017 10:29 PM, Miguel Giménez wrote: > original spare parts, and the three died months after. > Why this happen? Do I need to adjust laser current after change? Are > they basically unreliable? **IME modern lasers are not reliable devices. The older ones were very reliable. Why? Dunno exactly. If you look at an old laser from a Sony or a Philips CD player, you will likely see a very carefully (hand assembled?) laser unit, constructed from carefully machined aluminium alloy, precisely aligned, using a high quality glass lens. Replacement cost typically ran to several hundred Dollars. Modern lasers are all made in China, from plastic and steel and are almost certainly machine assembled. Cost, typically runs at around $20.00 or so. With massive cost reductions in any product, something usually has to give. -- Trevor Wilson www.rageaudio.com.au |
| ohger1s@gmail.com: May 31 12:18PM -0700 On Wednesday, May 31, 2017 at 8:30:01 AM UTC-4, Miguel Giménez wrote: > -- > Regards > Miguel Giménez Don't know about your particular drives, but anybody who did any kind of audio work in the 90s knows that Sony lasers were/are pure, unadulterated shit. I'm being kind here. There were tons of otherwise very nice Aiwa three CD carousel combo stereos that had decent power and respectable sound (given the market) and enough LEDs flashing to keep the Walmart buyers enthralled. Unfortunately, they all came equipped with Sony lasers. We pulled the plug on doing these after the first few failed and recommended that our customers use these for "garage" radios. Now I've heard that there were/are Chinese counterfeits for these and this might explain repeat failures, but it doesn't explain why so many Aiwa and Sony brand CD players came in for weak or dead lasers in two years. |
| whit3rd <whit3rd@gmail.com>: May 31 04:16PM -0700 On Wednesday, May 31, 2017 at 11:50:43 AM UTC-7, Trevor Wilson wrote: > reliable. Why? Dunno exactly. If you look at an old laser from a Sony or > a Philips CD player, you will likely see a very carefully (hand > assembled?) laser unit... Usual failure mode for a surface-emitting laser is some kind of dirt migration in the surface. This has NOT been getting worse, the chemistry and material preparation is as good now as it has ever been, and even UV semiconductor lasers are working well for long periods of time. Another possible reason for failure is ... lack of use. The normal electrical bias during operation is intended to keep sweeping impurities out of the sensitive region. If you just store the unit on the shelf, and DON'T operate it for a few hours a week, the (equivalent of) dust bunnies just pile up. The implication is, use your CD/DVD/BD readers and burners every week or so. They might just go bad on the shelf otherwise. |
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