COAX IS BEST

Cooltoff and others --

I don't think that the message here is go cheap. I think the message is look for quality at a moderate price.

I have been buying the monster cables in the $30 per meter/pair price range. The ones with the gold plated, screw-togather metal connectors. Recently I have seen that RCA has come out with a "Home Theater" line that looks exactly like these and sells for about $20 per meter/pair. I have seen these at Home Depot. Might be worth a look.

I am not really an advocate of the real cheep cables simply because I have not seen them hold up well. The cables that I mentioned are built well and are much less likely to go flakey over time or be flakey right out of the box as I have seen with the real cheap cables.

Hi Dave,

I should have been more specific in directing my comment. It was for Ron Davis.

I subscribe to most of what you have been saying and have also understood the directionality of the better cables.

I was just trying to confirm Ron's belief that for the digital cables there was little need to spend alot of money but that for the analog interconnects, there are better options than those that are supplied with the components.

To actually comment on the original question, listen for yourself and decide. A global answer isn't possible. Too many differences between too many components. And as Ron mentioned earlier, the differences between DACs is more of a factor that the cable.

And the RCA cables you mention, I believe, are made by Monster.

The search for the perfect sound never ends, and that's part of the fun.

Paul

Dave,

If the black wire in the interlink 300 is connected to ground on each end of the interconnect and the shield to only one end I believe the potential for ground loops is still the same (through the black wire). Wouldn't the black wire also make a connection to chasis ground on the amp side via the black wire, negating the directional nature of the shield?

Your common sense discovery efforts and expertise in this area are greatly appreciated.

Thanks,
Ron

Ron --

I believe you are correct. There is still a ground loop possibility via the black wire. However the shield still prevents the twisted pair from acting as an antenna picking up radiated signals.

This type of setup was originaly used for microphone connections where there was a long run of wire between the microphone and the amp input. The biggest benifit of this type of cable will be in hooking up an active subwoofer where the cable run is long.

I have never seen a problem with ground hum in any of my systems except ocasionaly with the phono inputs. I don't have a phonograph any more so -- no more hum.

The twisted shielded wire really works best where the connection is a balanced one meaning that both wires are hot one being positive and the other being negative (so to speak). In this case any signal coupled magneticaly appears in both wires but is cancelled by the balenced connection.

Using the twisted shielded wire in a single ended configuration with RCA plugs as the monsters (and every one else) is doing is a compromize from the ground loop standpoint. However, for most of us, our cable runs are very short (a meter or so). Also all the equipment is plugged into the same AC outlet therefore being grounded at the same place relitive to the house wiring. This tends to eliminate the ground loops.

The biggest sources of noise that I have encountered in systems that I have had over the years has been from ham radio operators and CB guys. The shield should help reduce that a lot.

Check out the following two links from Home Theater magazine:

[Link: hometheatermag.com]

[Link: hometheatermag.com]

I found it interesting that the difference between cables was judged to be more noticeable on PCM stereo from CDs.

I personally don't buy into the 'digital is digital' camp, not when a transmission system such as coax or optical is in the picture. Also, the whole system needs to be considered, not just the cables. With optical, there are optical transceivers and optical connectors added to the path at both ends(could this extra junk in the path explain why coax is usually preferred?). With coax, there are impedance concerns with the equipment as well as with the cables. I'd even bet that there are cables that are better matched to one vendors equipment verses another and therefore the reviews above are of little value.

It would sure be interesting to measure the bit error rates at the end if the coax or optical path(at the input to the D/A converters). That would settle a large part of this debate for me.

Doug

Doug,

Have you ever downloaded an MP3 file off of the internet? This involves transferring millions of bits of data, error free, over sometimes thousands of miles, God only knows how many terminations, transferring from copper to fiber and back again, and entering your computer through a skinny little telephone wire. If this can be accomplished without bit errors then surely we can pass our beloved audio signals error free over a 1 or 2 meter coax or optical cable.

For those of you who don't read the articles from hometheatermag, here are some choice clips.

"TARA Labs' Prism D-2 could be considered our second-place coaxial cable, although while Joe ranked it first and Dave ranked it second, I ranked it second-to-last. I think we all heard the same thing, but we simply felt differently about it."

"Our results with the other coaxial cables were really too random for us to produce meaningful rankings. For every cable one of us liked, there was another guy who didn't, and still another guy who thought it sounded about average."

This is quite a piece of work.
Ron

Check out this test of the finest digital coaxial cable in the world. [Link: magnani.net]

Ron,
Downloading a file over the internet involves protocols that provide error detection and error correction. Also, there are no realtime concerns as you have with streaming data. I suppose you've never heard noise or interference on your 'digital' cell phone either ;^). Don't get me wrong, I don't agree with the articles completely, but they do provide some reading approprite for this thread.
Doug

So exactly how is a digital coax defined? Is a simple Video cable or cat 6 with rca connectors? Is any good Audio cable ok to use or must it be video? Point of clarification.

Mike,

Follow the link on my last post.

Doug,

"You must remember that 5.1 audio is compressed. Compression means that you have removed all or most redundancy in the data stream. If so much as a single bit error is injected into the signal as it traverses between your DVD Player and your DD or DTS decoder, the decoder will not be able to uncompress the data. I don’t mean that it will distort or compromise the uncompressed data; I mean IT WILL NOT BE ABLE TO UNCOMPRESS THE DATA AT ALL. You will get a noticeable dropout (i.e. several seconds or more) while the decoder re-syncs on “error-free” data. This is the reason that Reed-Solomon forward error correcting coding is used on the data stream – NOT EVEN A SINGLE ERROR IS ACCEPTABLE. Because of the low data rates and short distances, I doubt seriously that a single bit error would creep in even if the Reed-Solomon coding was not used. But, it is used, and this type of coding can correct a string of 1000 bit errors and not even “breath hard”."

Quote from Harv, Administrater of the Dgital Theater Forum.

Ron,

Good info. My interpretation of the quote above is that DD 5.1 includes ECC (error correction code). If this is true, AND the ECC it passed on when it sent across the coax/optical then I will buy into 'digital is digital' for DD 5.1.

However, the quote only adresses Dolby Ditital, what about PCM data from a CD. Remember, quotes from the Home Theater articles stated that they heard more of a difference in cables when listening to PCM streams from CDs. I wonder what DTS uses also? Are there any real PCM bit-heads out there that can give us the scoop.

Doug

Doug,

More quotes from Harv.

When I addressed your question on digital audio cables, I specifically stuck to compressed data (i.e., AC-3 and DTS). PCM data is a totally different animal, but I’m also convinced that the selection of a cable for this application is also a non-issue. Even if you accept the premise that jitter can be injected by the digital interconnect between your CD Player and Receiver/PrePro, I do not believe that the length of this cable is sufficient to result in audible differences. If jitter is a factor, the interconnect cable is at best a third or forth order effect when compared to the mechanics of the transport. To my knowledge, there has been no controlled experiments (i.e., double or triple blind tests) conducted that would justify any other conclusion. As much as I would like to accept the testimony of individuals that claim to observe significant differences between various digital interconnects, without the necessary controls, these experiments are no better than uncontrolled testing of pharmaceutical products. Until controlled experiments are conducted, any observations must be categorized as “hear say”. The placebo effect is well documented and understood within the scientific community – if you pay a lot for a cable, by definition, it will result in better sound. The “psychological baggage” is just too strong a detractor to be ignored when attempting to conduct unbiased testing.

Rob,



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It's hard to imagine an encoding scheme that would allow for a recovery from a large number of bit errors while having errors in the checksum bits as well. Go figure, I guess that's why I'm a hardware guy.
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Surely, as a “hardware guy” you are familiar with error detecting and correcting memory. You add additional bits to a byte or word of memory to not only detect, but correct errors. These additional bits are just as susceptible to errors as the byte or word of memory you are attempting to protect. Therefore, any error correction scheme must not only address errors that might occur within the protected data, but also must address errors that might occur within the error correction bits. I presume you are familiar with Hamming coding – this is the scheme use in most error detecting and correcting memory. Hamming coding allows error correction across all bits within the data field whether they are associated with the byte or word being protected or the actual protection bits themselves. Depending on the sophistication of your Hamming implementation, you can correct errors from one to any number of bits. Reed-Solomon coding does the same thing and can be implemented in either hardware or software. RS coding can easily correct 1000 bits of error in a 10,000 bit data block. It is probably the most robust forward error correction code in use today.



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Either way, I'm not expert on AC-3. It's the fact that the clock is not sent in AC-3 that makes it unaffected by jitter.
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You seem to be saying that PCM data has a separate clock and AC-3 data doesn’t. Neither data stream has a separate clock. The clock for each signal type is derived from the data using PPL (phase locked loop) technology at the receiving end. This is the reason that jitter is generally considered a non-issue. Clock recover from a digital signal has not been “rocket science” for well over thirty years. There are plenty of integrated circuits that will do this job and create individual data and clock streams that are synchronized to a within a few nanoseconds (maybe even a few 100 picoseconds).

John,



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TCP/IP is just an error detection, not detection/correction schema. If a TCP packet is received which is corrupt a negative acknowledgement is sent and the sender resends the packet. If bit errors were endemic over the miles of crappy twisted pair performance of the internet would suck (oh wait, it does suck!), and using it would be virtually impossible.
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TCP/IP is actually not an error detection scheme; it is a high-level transport protocol. The error detection for TCP/IP is much lower in the ISO model and uses CRC technology. Despite your “grousing” about the performance of the Internet, as a programmer I would bet you regularly download multi-megabyte files and execute these without a problem. All it would take is a single bit error to send these executables off into space. As good as the data accuracy of the Internet is, it is not near as good as the Reed-Solomon protected link between your DVD Player and your Receiver/PrePro. Trust me, this link is “extreme overkill” for an audio application. The only reason for this is that you are dealing with compressed data. As I explained above, compressed data totally falls apart if so much as a single bit error is injected into the mix. If you are able to hear an AC-3 or DTS soundtrack, there is not so much as a single bit error in the reconstructed data stream – it is identical to what was recorded on the DVD.





Harv