Technical Interconnect ?

PolkThug · February 2005

Let's say you have two differenct rca style interconnects. You hook one up, play the first 30 seconds of a song and measure the max spl peaks across the audible range, then you do the same for the other interconnect. The only thing that changed for this test is the interconnect, everything else is the same.

Results show that the second interconnect spl peaks are 1-3db's lower than the first interconnect 90% of the time.

What conclusions can be drawn about the two interconnects (ie more capacitance/inductance etc.)?

Thanks,
PolkThug

HBombToo · February 2005

I am assuming that these are analog interconnects. My first best guess would be the resistance between the 2 are the source of your loss. Contact resistance and cable resistance are the first 2. As far as C & I there probably is a small contribution but considering the lengths at 1m the impact is probably negligible.

HBomb

PolkThug · February 2005

Yeah, analog 1 meter. I think "resistance" is the word I was looking for. So, different materials and substances would have different resistances to electrical signals, right? (kind of thinking out loud here)

I'm thinking that resitance in analog interconnects would probably be a bad thing. Resistance is measured by Ohms, right?

Thanks,
Toby

HBombToo · February 2005

Originally posted by PolkThug
Resistance is measured by Ohms, right?

Thanks,
Toby

Yes Sir. If you don't have a VOM I can loan you mine...

PolkThug · February 2005

I know that the ideal component cable is 75Ohm rated. Is there an ideal Ohm rating for an analog interconnect that anybody knows of?

bknauss · February 2005

You're not going to lose that much power due to cable resistance. Either the second interconnect is bad or something else was screwed up between tests.

PolkThug · February 2005

Originally posted by bknauss
You're not going to lose that much power due to cable resistance. Either the second interconnect is bad or something else was screwed up between tests.

For now, lets assume that the testing procedures are perfect. You take an rca interconnect that measures 75Ohms, then, alter the cable in some way, which raises the Ohm rating to 80Ohms. Could this lower the final output? Or, if the Ohms are less, could this raise the final output?

unc2701 · February 2005

Almost deffinitely impedence/resistance. And the quieter cable is probably a video cable... Video cables should be around 75ohms and coaxial; audio cable should be much lower resistance (5-15 ohm is typical) and twisted pair. How the amp knows how loud to go is based on the voltage on the wire. If the wire has high impedence, some of the voltage is converted into heat and you get a lower voltage at the amp end of the line, thus it's quieter.

Those resistances I gave are in terms of some set length... like a 1000 meters? maybe? So an ohmmeter might not show exactly what you're expecting.

HBombToo · February 2005

Originally posted by PolkThug
For now, lets assume that the testing procedures are perfect. You take an rca interconnect that measures 75Ohms, then, alter the cable in some way, which raises the Ohm rating to 80Ohms. Could this lower the final output? Or, if the Ohms are less, could this raise the final output?

Toby the 75 Ohm cable is for digital not the analog and it is not an end to end resistance. The 75 Ohm is determined by the Id, Od and dielectric separating the two of the line and is intended to match the input and output resistance of the terminals you are connecting. A 75 Ohm cable could be measured end to end but will have a very low resistance just like the analog cable.

Henry

bknauss · February 2005

Easier thing to test... take a multimeter and place a probe on either end of the cable (the signal part of the barrel). If you're getting something more than milliohms, then something is definitely up.

izafar · February 2005

http://www.audioholics.com/techtips/audioprinciples/interconnects/componentvideocables.php
this is a good article about coaxial cables

PolkThug · February 2005

Originally posted by unc2701
audio cable should be much lower resistance (5-15 ohm is typical) and twisted pair. How the amp knows how loud to go is based on the voltage on the wire. If the wire has high impedence, some of the voltage is converted into heat and you get a lower voltage at the amp end of the line, thus it's quieter.

Those resistances I gave are in terms of some set length... like a 1000 meters? maybe? So an ohmmeter might not show exactly what you're expecting.

Okay, this makes sense.

PolkThug · February 2005

Originally posted by HBombToo
Toby the 75 Ohm cable is for digital not the analog and it is not an end to end resistance. The 75 Ohm is determined by the Id, Od and dielectric separating the two of the line and is intended to match the input and output resistance of the terminals you are connecting. A 75 Ohm cable could be measured end to end but will have a very low resistance just like the analog cable.

Henry

more good info. thanks.

Tour2ma · February 2005

While the wire should not produce significant resistance differences over such a short run, there is more than just the wire to consider...

Wire connections to the terminations...
Terminations' connection to the RCA jacks...

While the former is included in a bench, VOM measurement, the latter is not...

PolkThug · February 2005

Originally posted by Tour2ma

Wire connections to the terminations...
Terminations' connection to the RCA jacks...

This is more in line with what I'm doing.

PolkThug · February 2005

Can someone here host a file for me. I got to do a review of a product for a manufacturer over the last few days, that's why I was asking all these questions.

Thanks,
PolkThug

Technical Interconnect ?

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