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In Reply to: Neg. feedback? It's probably your cheap cables you're hearing....(nt) posted by mkuller on August 22, 2006 at 12:25:03:
The most valuable posting I ever read on the internet about cables was authored several years ago by John Curl. He said he measuered noise from the 7th harmonic of 5 khz down -120 db for the cheapest $1 Radio Shack interconnect cable (the worst he could find) and down -135 db for the best cable he could find. This dispelled any lingering doubts I might have had about inexpensive interconnect cables being far more than adequate for use in ANY sound system. This hardly came as a surprise to me though since every test I tried where a 7 mhz video signal with over 350 times the bandwidth of a high fidelity audio signal appeared indistinguishable from the same signal sent to the same TV set as an RF signal for decoding by the TV set's own tuner. (The TV was Sony 36" Wega XBR extra bright and the source was cable TV feed to a VCR.) This is testimony to the dead flat FR of the cable and its immunity to noise at least in that application on that day. It is also in perfect agreement with my own A/B audo tests in which they are alternately inserted in the signal path an shunted by a preamp's tape monitor switch. Inexpensive cables have also never failed to sound indistinguishable to me from the shunt. Since I don't consider a cable a control element and I think most electrical engineers would agree, I consider any cable which performs differently from this to be defective and any cable more expensive that this to be an unnecessary waste of money. Nope, whatever the cause of the poor performance in Dan's setup, it wasn't the cable...unless of course he was foolish enough to use audiophile cables (sound's instead like he used Belden which is excellent.)
Follow Ups:
When you compare a Yugo to a Pinto, you compare red delicious apples to red delicious apples. You need to throw some braeburn, granny smith, fuji and golden delicious into the mix to better understand the differences in flavor. And to do so, you must taste them. Don't dismiss them based on the way they look.BTW, did you ever get around to compiling that list of recordings adored by audiophiles and the ic's/cables used in the studio to record them with?
Until then, what you have to say about it is gibberish to me.
You may have problems with your Sony or your vcr.
Every video cable I have tried had visible differences and I have used TV sets ranging from 20 inchers to large 60 inchers. On the samller sets the differences tended to be smaller, but not so on the larger sets, including a Sony 34" set I tried various cables on. The RS cables sucked: picture was grainy and edge definition was not very clear with poorer color saturation. Geez, I can see the difference with RG-59 and RG-6 using the cable TV ends....
Stu
I have four of these KV-36XBR250s I bought in 2000 and every one of them has performed flawlessly from the day I got them. BTW, they work beautifully with DVDs too. Never experienced any of the problems others reported with this and similar models on Audio Review's site. Very pleased with both their picture quality and reliability.
(nt)
.
"7th harmonic of 5 khz "Could you hear the 7th harmonic of 5Khz anyway even if it was full scale? lets see fundamental is 5Khz
2nd harmonic 10Khz
3rd 15Khz
4th 20Khz
5th 25Khz
6th 30Khz
7th 35Khz!!Gee, Soundmind, you are right it doesn't matter if one is at -120db or -135db at 35Khz!! You are just brilliant!
Now if it was the 7th harmonic of 500Hz it might be a different story because this would be smack in the middle of one of the most sensitive regions of your hearing.
The first harmonic of 5 khz is 10 khz, 5 khz is called the fundimental but what difference does it make. If you don't like it, don't blame me, take it up with Mr. Curl, it was his posting. BTW, even if it was the 7th harmonic of 500 hz, it would still be at 7khz and -120 down is good enough for government work as they say and it's good enough for me. That's much better than most electronic equipment.
Morricab, I measure at 5KHz, BECAUSE it is convenient for me to do so, especially when I am looking for xover distorion in power amps. 500 Hz would be OK, but my test equipment today is finely tuned for 5KHz and it works best there with the settings inside my test equipment. It would measure the same amount in level. I have checked this, but I do not use it for normal measurements. I also have IM from the same tester, and it is better at measuring low frequency garbage.
Hi John,
I wasn't criticizing your measurements as they seem fine for whatever purpose you had for them. I was criticizing soundmind's use of this as a reason why cables all sound the same and that the frequency of the 7th harmonic of 5Khz is so high that he wouldn't hear it regardless of level.
" I was criticizing soundmind's use of this as a reason why cables all sound the same and that the frequency of the 7th harmonic of 5Khz is so high that he wouldn't hear it regardless of level."I clearly didn't say all cables sound the same. Quite the opposite, I have complete faith in the ability of tinkerers who don't know what they are doing to find endlessy ingenious ways screw up anything and then find people they can convince that their inferior product is actually better than the far cheaper alternative which functions perfectly. In audio, this has been turned into an entire industry. I also said that insofar as the only legitimate function of an audio interconnect cable for a consumer audio system, the inexpensive interconnects function as perfectly as can be desired and any problems with the performance of a sound system would be far better off resolved by investigating and changing other areas than to experiment with expensive, unpredictible, uncontrollable audiophile type cables.
You said, "He said he measuered noise from the 7th harmonic of 5 khz down -120 db for the cheapest $1 Radio Shack interconnect cable (the worst he could find) and down -135 db for the best cable he could find. This dispelled any lingering doubts I might have had about inexpensive interconnect cables being far more than adequate for use in ANY sound system."If this isn't another way to say, "they all sound the same look at how low the distortion is on even the cheapest cable" then please by all means tell me what you mean.
"I also said that insofar as the only legitimate function of an audio interconnect cable for a consumer audio system, the inexpensive interconnects function as perfectly as can be desired and any problems with the performance of a sound system would be far better off resolved by investigating and changing other areas than to experiment with expensive, unpredictible, uncontrollable audiophile type cables. "
Sorry but this is just a very roundabout way of saying that "all cables sound the same and even if they don't the expensive ones that sound different to the cheap ones must be F*(ç/*" up". How do you know the inexpensive cables are designed properly?? Have you tested them yourself? Has anyone bothered to actually test the giveaway cables or cheap radio shack ones?
a
John Curl's test of the ic's had some validity. It is the interpretation of the results that is in conflict.John pointed out differences between cables as they were tested on a specific machine....his
The AP sports much better specifications than JC's rig, and therein lies the distinction. Having been designed to more rigorous specs, issues which affect JC were eliminated via engineering in the AP rig, whereas John attempted to better his old rig without baselining it.
I certainly can believe John found repeatable differences, but Bruno's results prove that it is a cable/rig interaction, not some nefarious diode/zero-crossing distortion.
THAT needs to be researched, as it is that interaction that is far worse in the home environment.
A shame it was not continued, as it is a good avenue of research.
Cheers, John
Reactive loading of the output driver. What's your guess?
d.b.
Dumb guess, Dan. If you had the schematics you would see that the oscillator and its output driver are completely resistively buffered from the cable itself. Also I deliberately put a relatively large capacitor (.033uf) to ground designed to attenuate anything over 5KHz on the oscillator and therefore improve both the S/N of the oscillator and its residual distortion, as well as to have a predictable cap load buffering any changes in cable capacitance. The distorion itself still looks and measures like mini back paralled diodes in series with the wire. It is most probably PIM distortion in the return shield interface with the rca connectors. This could probably have been ignored by the Audio Precision, but important with the ST. I also wish to say that the examples provided to me were very well soldered, when they were custom made, and in general measured better than other examples on my workbench.
We've been through this already, if you wnat to continue, be my guest. I'm still not convinced that your resistive buffer is the total answer on this.
Have a nice day;
d.b.
jc: ""
If you had the schematics you would see that the oscillator and its output driver are completely resistively buffered from the cable itself.""
Since he doesn't have the schematics, it can't be called a "dumb guess", silly..:-)jc: ""
Also I deliberately put a relatively large capacitor (.033uf) to ground designed to attenuate anything over 5KHz on the oscillator and therefore improve both the S/N of the oscillator and its residual distortion, as well as to have a predictable cap load buffering any changes in cable capacitance.""Hmmm, new point of info..
When you say "ground", where are these bad currents going? Since ground is not an infinite sink that forever removes electrons, perhaps the ground currents were indeed coupling to the cable loop via some chassis path....an interesting thing to look at..
Cheers, John
My concern is more that the physical loop caused by the cable and the test widgit had an interaction with chassis currents of the drive signal.John noted that cleaning the contacts of the ic's changed the results, and he got more consistent readings when he cleaned them.
A shield interaction would do that.
So, I do not think it was a reactive loading issue, simply because the load would not change that much when the contacts were cleaned.
Cheers, John
Yes it's been done, and all that was found for distortion was the residual distortion of the analyzer.
d.b.
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