wire/interconnect help

[MR M.l.]

I just recently purchased a fairly expensive system:

60 inch sony lcd rear proj.
denon 3805
deno 2910
paradigm s4's
paradigm seismic 10
paradigm in wall rear spakers
paradigm cc470 center.

Maybe it is the accoustics of the room but the sound quality is not the same as when I listened in the store. I listened to elton john's goodbye yellowbrick road and there seemed to be a hum during the first few songs. Is the system that good that it will pick up imperfections in the cd. Can anyone suggest some music that will be a good test for the system.
I was not there during the install. How do I check to see if the best/proper interconnects and wiring were used. The wires seem to be jumbled together
and it is difficult to get behind the tv. Any suggestions would be greatly appreciated.

 

[Privateer]

How do you have the system hooked up, what type of speaker cable are you running, have you tested the AC power in your house?

 

[Mort Corey]

If things are really "jumbled" up, it could be part of a problem though you would think that it would be present on ALL songs on any particular CD vs just a few. Generally, you want power cords isolated (as much as possible) from any video source and not crossing over any coaxal audio cables (optical cables should not be effected). Take the CD into the store where you purchased your gear and play it in their listening area on their best equipment. Nice gear BTW.

Mort

 

[tbewick]

You should check out the Stereophile website, it has a section called 'Records to die for', which lists some good recordings.

I've listened to CD's which have background noise and it is perfectly normal. To check if your cables are adding noise, try running the same piece of music through digital interconnects instead of phono ones. They will add no background noise, but they may however restrict the sound bandwidth and possibly add jitter.

 

[jaxvon]

What? Digital cables restricting bandwidth and adding jitter?

Unless I'm insane, I don't see how sending the digital signal to another component would restrict the bandwidth. Unless you're trying to make a 100ft run.

 

[j_garcia]

What Mort said. What you will want to check is how the system is set up. My first guess would be that something is not configured correctly. Wires and interconnects play the smallest role in the chain, so the issue would be more likely that something is not connected correctly, or the appropriate connection was not used, rather than cheap/bad cables.

In the store, were those speakers being driven with similar gear? I would really have to say that the 3805 does not quite have enough power to drive the Signatures.

Very nice speakers. I auditioned the S2s and was very impressed with them.

Digital cables shouldn't add jitter. Jitter is a function of the D to A conversion, not the cables themselves, if that is what you are getting at. While there is a limit to the bandwidth of those cables, the signals passed along them should be well within those limits.

 

[mkossler]

You also may wish to check that you do not have a ground loop affecting your setup. Take a look here:
http://www.audioholics.com/techtips/setup/avhardware/groundloopcableTV.php

good luck!

 

[mtrycrafts]

What? Digital cables restricting bandwidth and adding jitter?

Unless I'm insane, I don't see how sending the digital signal to another component would restrict the bandwidth. Unless you're trying to make a 100ft run.

Glad someone else jumped on this. I don't know if I have enough pristine skin left

 

[mtrycrafts]

While there is a limit to the bandwidth of those cables, the signals passed along them should be well within those limits.

If those digital cables, same as video cables, 75 ohms can pass TV signals up in the high mHz or gHz, you will not have a problem with digitized signals in the low mHz range

 

[mtrycrafts]

I would only add that you also need to check out the TV video feed from the wall. You could have a ground loop issue?

 

[tbewick]

The issue of bandwidth restriction was something I saw on the 'Sound On Sound' magazine website, and was directed towards toslink cables. As for jitter, though it may be inaudible/very difficult to hear, it can exist in poorly designed external DAC systems.

You can run a test on your system for jitter, by running two different test tones on your CD player and checking if the noise floor changes for each tone.

 

[mtrycrafts]

The issue of bandwidth restriction was something I saw on the 'Sound On Sound' magazine website, and was directed towards toslink cables. As for jitter, though it may be inaudible/very difficult to hear, it can exist in poorly designed external DAC systems.

You can run a test on your system for jitter, by running two different test tones on your CD player and checking if the noise floor changes for each tone.

Yes, some plastic optical cables may be limited but it will pass digital audio very well, none the less.

Jitter is an issue of timing. So I don't see how your test will tell jitter when jitter is measure in the nano seconds. You need a whole bunch to be audible.

 

[MDS]

Jitter is an issue of timing. So I don't see how your test will tell jitter when jitter is measure in the nano seconds. You need a whole bunch to be audible.

I don't see how the test will do anything either and just for the record, a 'good' adc/dac will have jitter measured in picoseconds (trillionths of a second). Ain't no way the human ear can detect a timing error of 30 trillionths of a second.

A few years ago I was looking for research data to see if anyone has measured the minimum threshold where a human could detect a difference in sound. I never did find any publicly available (mtrycrafts, WmAx any pointers?) I did have a few discussions with some of the recording engineers on the Sound Forge forums and none of them had any definitive references for me, but most thought it was around 6 ms.

The reason I was (am) interested in any studies is that I was attempting to determine just how many samples in a row at the maximum value (the definition of 'clipping' for digital audio) it takes to be audible on general music. Sound Forge uses a simple 'over' counter, which happens to be set at 4. So 4 consecutive max value samples will light the clip indicators but on every CD I have ripped that lights the clip indicators, said clipping is entirely inaudible to me.

 

[mtrycrafts]

I don't see how the test will do anything either and just for the record, a 'good' adc/dac will have jitter measured in picoseconds (trillionths of a second). Ain't no way the human ear can detect a timing error of 30 trillionths of a second.

A few years ago I was looking for research data to see if anyone has measured the minimum threshold where a human could detect a difference in sound. I never did find any publicly available (mtrycrafts, WmAx any pointers?) I did have a few discussions with some of the recording engineers on the Sound Forge forums and none of them had any definitive references for me, but most thought it was around 6 ms.

The reason I was (am) interested in any studies is that I was attempting to determine just how many samples in a row at the maximum value (the definition of 'clipping' for digital audio) it takes to be audible on general music. Sound Forge uses a simple 'over' counter, which happens to be set at 4. So 4 consecutive max value samples will light the clip indicators but on every CD I have ripped that lights the clip indicators, said clipping is entirely inaudible to me.

Are you looking for thresholds in reference to time, how long something has to be played to be detected?
There are a number for amplitude, jutter and distortion:

"Theoretical and Audible Effects of Jitter on Digital Audio Quality", Benjamin, Eric and Gannon, Benjamin, 105th AES Convention, 1998, Print 4826.

"Clock Jitter, D/A Converters and Sample Rate Convertions", Adams, Robert W., 95th AES Convention, Print #3712.

"Theory and VLSI Implementation of Asynchronous Sample Rate Converters", Adams, R. A. & Kwan, T., 94th AES Convention, 1993, Print #3570.


"Level Discrimination as a Function of Level for Tones from .25 to 16khz", Florentine, Mary, et al, Journal of Acoustic Society of America, 81(5) May 1987, pg 1528-1541.

"On the Relations of Intensity JND's to Loudness and Neural Noise", Zwislocki, J and Jordan H., Journal of Acoustics Society of America, 79(3), Mar 86, pg 772-780.

"Auditory Intensity Discrimination at High Frequencies in the Presence of Noise", Viemeister, Neal F., Science, vol 220, 16 Sep 83, pg 1206-1208.

"Speaker Cables, Measurements vs Psychoacoustic Data", Villchur, Edgar, Audio, Jul 94, pg 34-37.


And Moir has one on distortion, I need to look for it in my library

 

[Snap]

Mr. MI,
You said that you were not there durring the install. That leaves me to believe that the Audio Store did the install? If they did then call them back! You should not have "jumbled" wires if it was a clean install. Jumbled to me translates that you think it is a rats nest of cables instead of a clean install.
On other thing you not related to the hum, "break in" I have almost the same system except Phase Tech speakers. The Denon sounded better to me after a week or so of use.
If you did have it installed then they should not have left you with a system that has a hum.
Som one else also stated make sure that your power cords are away from your interconnects if possible. (once again the installers should have done that for you.)

 

[msmith855]

Mr. MI,
You said that you were not there durring the install. That leaves me to believe that the Audio Store did the install? If they did then call them back! You should not have "jumbled" wires if it was a clean install. Jumbled to me translates that you think it is a rats nest of cables instead of a clean install.
On other thing you not related to the hum, "break in" I have almost the same system except Phase Tech speakers. The Denon sounded better to me after a week or so of use.
If you did have it installed then they should not have left you with a system that has a hum.
Som one else also stated make sure that your power cords are away from your interconnects if possible. (once again the installers should have done that for you.)

Going to have to second this notion, half this conversation went way over my head (lol), but the bottom line is you paid a lot of money on equipment (and I would guess on the install itself) call them back and make them do it until they get it right. They shouldn't leave the house until you are satisfied with the sound.

On a side note, the setup will never sound the same as it did in the store, acoustics of the room, other equipment differences, etc will always play into that... but if you think something sounds "wrong" and you paid for a professional service... they have an obligation to make sure it's done right.