Axiom Home Page Forums General Discussion Home Theater interconnects

Okay, I've decided to do it. I'm posting the question on interconnects... by now, we've all had our fun with the speaker cable question, but interconnects came up. I actually am quite interested in what makes a good interconnect. I know the contruction of the connector is a good reason to buy good interconnects, but other than that, any reason to buy good ones? How about fiber optics, what makes a good one?

For my interconnects, i have nothing expensive but enough to replace out of the box vcr cabling for sure. At most i wanted the usual copper or silver conducting wire (copper being cheaper) and have the wire housed in a sheath of some sort to cut down the EMF. I have found that with slightly better cables in my computer i have better reception with my cell and cordless phone in my office. The electrical interference generated is really alot more than one may think. But beyond that, i have yet to pay anything more than ten or fifteen bucks each for a/v cables, composite vid, toslink, etc. Most of what i have were ebay sales and most are Acoustic Research by brand (just by chance).

Nortel makes some pretty good fiber optic cable and i'm sure you can get it dirt cheap these days (both the cable and Nortel that is).
I find that the optical or digital coax connections provide a higher sensitivity from my cd player (vs hooking it up via RCA analog connections) but the sound is not really different.

Someone was telling me the other day though that if you use optical/coax digital from your cd player, you actually circumvent the DAC onboard your player and instead the DAC of the receiver is used. But if you use analog connections then the DAC on the player is the sound you hear instead.
If anyone has an idea what this person may be referring to, i'm all ears.

As far as the DACs are concerned, I'm certainly no expert, but what you say is true. The digital signal from the CD player is converted by the player's DAC (digital-analog-converter, I think) to an analog signal, then ported through the analog connectors to your receiver/processor. From there, the analog signal may be converted to digital and back again for bass management and other "digital sound processing" (DSP). There are those that think that all this converting and back again can result in signal distortion and a decrease in your sound quality.

More practically for me, I recently upgraded my old receiver to a processor with high quality DAC. My 13 year old CDplayer has had marginal sound, but I was using the analog output and a 13 year old DAC (the new DACs have much higher resolution). I had an instant "upgrade" 2 days ago to my CD player when I switched to a digital cable and utilized my new processor's DAC. Now, it sounds pretty darn good for an old mass market player! So it depends on the comparative quality of your 2 components, I think. If one DAC is better than the other, you're probably better off using that one. So you might get better sound using your analog outputs from your player, if your player is newer and higher quality than your receiver.

ChrisR

So lemme get this straight.
If i use analog connections, the cd player DAC converts digital to analog, carries it to the receiver, the receiver DAC turns that analog back into digital and plays the sound.
But, if i use digital connections, then the digital signal from the cd player goes DIRECTLY to the DAC onboard the receiver and hence NO processing occurs within the cd player.

Is that right?

So the question is then, as you sort of state, do you want to use the DAC onboard the cd player or on the receiver? Then answering that question will allow you to choose either analog or digital connection for cd to receiver.

As i was explained this earlier, the DAC on the cd should always be used preferentially over the receiver DAC since they are TYPICALLY of better quality due to their single use design (couple of assumptions here of course that both units are relatively the same age technology, quality/price range, etc.).
Hmm, i guess i should probably be comparing the DAC specs on my receiver and cd players then before committing to any new cd player/ dvd purchase.

Hi guys!

Well as best as I can tell, ChrisR has it correct in his assessment of the process of digital to analog conversion. And chesseroo, your first paragraph is also right. And you may be correct in that it could be time to compare DAC specs for receivers and DVD/CD players (if you can get that info). Whether (and when) a receiver converts a digital input signal to analog (for processing) is a design choice/option. Indeed, most units would keep the signal digital for any internal processing and only convert the digital signal to analog just prior to final amplification.

I have tried (and thus currently use) both a digital and an analog connection from my DVD player to my receiver. The analog connection is to the CD input. There IS a slight difference in sound between the two and the digital input is a bit "louder" (i.e. more sensitive OR the DVD digital output is higher) Anyway, the point here is that things in this arena are just getting more complicated all the time. Wanna hear a difference between a 192kHz/24bit DAC and a 96kHz/16bit one? WOW! gimmie more bits and khz anyday!

One other thing to consider - and this is not much of a factor anymore. Due to anti-copying considerations, some equipment (receivers) will not provide a digital output (to be available for copying) when using a digital input source (such as from a CD/DVD player) - for the very reasons of the purity of the unconverted (and unprocessed) digital signal being used. Its true that everytime a signal is converted back and forth, some type of distortion is added in. And thus the record companies are not too concerned about analog copying anymore.

Time to dump that old equipment with the inferior DACs!

Randyman

I'm using the optical connection between my DVD player and Onkyo 787 receiver, and I was shocked at how much better the optical connection sounded. It's much more dynamic and crisp sounding. I think it only became more obvious since adding the Axiom speakers.

When i was talking to a stereophile friend yesterday, his recommendation would be to use the optical connection for dvd to get that crisp, clear sound for the movie theatre experience but to use the analog for music.
However my dilemma was that i started off by looking for a dvd player to double as a cd player as well. Obviously i cannot use both the optical and analog connections unless the Onkyo receiver can actually switch between the two, and i don't think i paid enough money for such an option.

So instead, i'm now looking for a single dvd tray and will look around for a good used cd player 5 tray. Ebay here we come again!!

Ok then onto the next question.
Can someone explain to be the following:
"8 bit Burr Brown"

Hello Randyman, Ravi, Chesseroo, and ChrisR,

Getting back to Ravi's question on interconnects, a few comments: Of course, mechanical integrity is important, and, if you're running analog line-level signals more than a couple of metres (6 feet or so), so is the interconnect. Long shielded cables can have capacitance effects that will affect high-frequency response. If the latter is attenuated, you might perceive those changes subjectively as a "loss of imaging, or clarity, or a reduced soundstage", because all those are affected by reduced upper-frequency losses.

If you're using a turntable, the aforementioned capacitive effects become pronounced because the signal from a magnetic cartridge is only a few millivolts, and from a moving-coil cartridge, it's even tinier (microvolts). So don't use a cable between the turntable and preamp longer than 6 feet, unless it's ultra-low capacitance cable. (Capacitance is measured in picofarads--pF--per foot of cable and is sometimes stated in cable specs.)

Remember, however, with digital signals and coaxial or optical digital connectors, we're talking about PCM (pulse-code modulation)--just on and off pulses, the mathematical sequence of which "describes" the original analog signals from the microphones. On a CD or DVD, there is a huge amount of error correction (redundancy) always operating to fill in and replace any missing data. Frankly, I've used cheap and expensive coaxial digital interconnects and never heard a difference, nor should there be any if you understand how the above digital signals work. Nor is there any audible difference with optical digital connectors.

With analog video, we're talking major differences with long interconnects because video signals are MILLIONS of Hz (megahertz). Because video frequency response correlates directly with on-screen resolution, any loss of video response with long interconnects (15 feet or more) will show up on-screen as a loss of sharpness and clarity. I've only done tests with long shielded cables carrying composite video sigals; I presume the same factors would apply to S-video and component-video cables as well. So if you're running long video cables to a projector, it's worth getting really good-quality interconnects.

Regards,

Hello Alan

thanks for your response, it was very helpful, and was pretty much what I thought was true.

It leads me to another question, however. If attenuation is a big worry in interconnects, as well as interference, then wouldn't this also be true of speaker cable? If not, what is the difference between the two that makes it un-true.