Hello, regarding the Cambridge Audio 840C, are there differences between the DAC and CD Player functions, in terms of sound quality?
If yes, in which cases, and how could you avoid it?
The 840C, as with any other CD player that has digital inputs, will sound best when playing a disc rather than decoding an external digital source. Any time you have an SPDIF interface in the signal path, the sound will be degraded. There's no getting around it, unfortunately.
I have not heard that S/PDIF causes signal degredation. On the contrary, it is one of the preferred digital transfer protocols. From Wikipedia: (my bold for emphasis).
S/PDIF was developed from a standard used in the professional audio field, known as AES/EBU which is commonly used to interconnect professional audio equipment. S/PDIF remained almost identical at the protocol level (consumer S/PDIF provides for copy-protection, whereas professional interfaces do not), but changed the physical connectors from XLR to either electrical coaxial cable (with RCA jacks) or optical fibre (TOSLINK, i.e., F05 or EIAJ Optical), both of which cost less and are easier to use. The cable was also changed from 110 Ω balanced twisted pair to the already far more common (and therefore compatible and inexpensive) 75 Ω coaxial cable, using RCA jacks instead of the BNC connector which is common in commercial applications. S/PDIF is, for all intents and purposes, a consumer version of the AES/EBU format.
Note that there are no differences in the signals transmitted over optical or coaxial S/PDIF connectors—both carry exactly the same information. Selection of one over the other rests mainly on the availability of appropriate connectors on the chosen equipment and the preference and convenience of the user. Connections longer than 6 meters or so, or those requiring tight bends, should use coaxial cable, since the high light signal attenuation of TOSLINK cables limits its effective range. On the other hand, TOSLINK cables are not susceptible to ground loops and RF interference like coaxial cables. One deciding factor for many is cost—any standard 75 Ω A/V cable can be used for coaxial connectivity, while TOSLINK requires a specific cable which until recently was not very affordable.
Where have you heard that S/PDIF causes signal degredation?
It's well documented that SPDIF degrades fidelity, that different cables carrying SPDIF sound different, and that different methods of transmitting the bitstream (coax, TosLink, AES/EBU) change the sound. See the AES paper "Is the AES/EBU/SPDIF Interface Flawed?" by Malcolm Hawksford and Chris Dunn.
What about using USB to a Squeezebox and then digital out to 840C digital input? While my listening has been very limited this sounds better to me than just the squeezebox and markedly better than SPDIF.
I have the 840C, and have 2 devices connected to it via the coaxial inputs. A Pioneer Elite 100 disc cd changer, and an Iomega Screenplay 500GB multimedia hard drive. The music on the hard drive are WAV files burned from my vinyl collection.
Listening to the cd changer via the 840C is a huge improvement over listening to the cd changer alone. The same with the Screenplay hard drive. It sounds great when listened to via the 840C, in fact a little better than the cd changer via the 840C.
Listening to the same music via cd in the 840C is definitely an improvement over the DAC function. More clarity and detail, and better defined bass. However, the change is not so large that I will do this all the time. Only for serious listening sessions. The sound is so good via the DAC, and combined with the convenience of lots of music on the cd changer or the hard drive, its tough to beat. I've also found that there are big gains to be made by using a better quality coaxial cable to feed the DAC. Won't get into the debate on why this is, my ears like what they hear. I did find that the sound is much better via coax than it is when using the TOSlink connection. My cd changer has both coax and toslink and I can A/B listen, and the coax is much better in my setup.
I am guessing the sound via the 840C would be even better if the balanced outputs were used, but I don't have an amp with that capability, so I'm using RCA connections to the amp via some good quality Nordost cable.
The 840C is a great CD player, and a great DAC. My CD collection which had gone stagnant, is revived and I can actually buy CD's again. Was listening to only vinyl before, but now I can listen to either depending on what music I want to hear and don't feel let down when switching to either format.
"The music on the hard drive are WAV files burned from my vinyl collection.
Listening to the cd changer via the 840C is a huge improvement over listening to the cd changer alone. The same with the Screenplay hard drive. It sounds great when listened to via the 840C, in fact a little better than the cd changer via the 840C".
I am wondering if you can try burning your CD to the hard drive in a lossless format. I use iTunes Apple lossless. What I'm thinking is that if the files were lossless rather than just wav, which has far less "musical" information, the comoarison would be more fair.
I am torn between a seperate DAC (CA's DAC Magic, PS Audio's Digital Link III, Bryston's new DAC, etc) or using the digital option on the 840C. I have a Squeeze box still in the box! I am also getting the new Oppo 83 (hopefully tomorrow) and I am very interested in your thoughts on lossless files. Decisions, decisions . . . .
The WAV files to my knowledge are lossless. A typical 3 minute song is ~50MB in size. I have also burned many store bought pre-recorded CD's to the hard drive in WAV format, and then burned the WAV files back to CD-R. In every case, I hear a distinct improvement in the sound of the newly burned copy over the original. Without exception, my burned copies of vinyl in WAV format always sound better than the pre-recorded CD's of the same music. This includes lots of jazz, and every type of rock genre imaginable.
I also have the Dacmagic which I use for my second system. I have a Dell laptop (with Vista), and an external drive full of music in WAV format. The laptop is connected via USB to the Dacmagic. Since it is USB, it only allows for 44.1 or 48 khz, but 44.1 being standard CD sounds very good via the Dacmagic. The dacmagic is connected via RCA to my NAD C372.
However, I would not compare the Dacmagic to the DAC portion of the 840C. The 840C has a better built in DAC. I have tested them side by side in my main system. The Dacmagic sounds very good, and is also a good upgrade for my cd changer and my DVD (Denon 1920 DVD-A, SACD capable), but it does not have as much air or refinement as the 840 DAC. Not to turn anyone off the Dacmagic. I consider this a very good purchase and I'm getting tons of use out of in my second system. It's playing a burned copy (vinyl) right now of the Beatles Let it Be - Naked. I have an external soundblaster X-FI that connected to the laptop, but it 's not even close to the quality of the Dacmagic. Note that the Dacmagic should be left turned on for a few weeks, rather than on/off during use. This type of continuous burn-in eliminated the original thinness of the Dacmagic, that others complained of and which I heard. Now it's sounding great, good midrange, good highs, and full bass. I have not heard the PS Audio DAC, or the Bryston, but they get good reviews and might be better than the Dacmagic. Tough call unless you can A/B them, or if you can find some reviews where the reviewer thinks they are a good step up in sound over the Dacmagic.
I;m also waiting for the new Oppo blu-ray player, it's in shipping now. I've only purchased that though for blu-ray movies, and for the SACD and DVD-A capability to replace my Denon universal. I don't plan to use it as a transport for the DAC in the 840C.