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Alexander

Coax cable used in interconnects - impedance effect on equipment?

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What if any effects would a typical coax 75ohm based interconnect cable have on the device(s) in is connected ti?  Not sure what if any impedance would exist on a shielded twisted pair equivalent.

 

 

 

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I have the SVS Sound Path interconnects, twisted pair construction.  They have an impedance of 110 Ohms.

 

Quote

 

  • Conductor DCR: 77 mΩ/meter
  • Shield DCR: 30 mΩ/meter
  • Nominal Impedance: 110Ω
  • Nominal Capacitance: 39 pF/meter @ 1kHz
  • Rated Bandwidth: DC-5.0 MHz (3M cable) with ≤1.1 VSWR and ≥27dB Return Loss
  • Resilient, cotton-braided jacket forms the 5th layer of the RFI Shield

https://www.amazon.com/d/RCA-Cables/SVS-SoundPath-2M-RCA-Interconnect/B0197UUMD8/ref=sr_1_3?s=electronics&ie=UTF8&qid=1547814609&sr=1-3&keywords=svs+cables


 

 

Check out the construction of this Monoprice RCA cable:

https://www.monoprice.com/product?c_id=102&cp_id=10218&cs_id=1021810&p_id=18537&seq=1&format=2

+++

 

Your question was, what difference is there between 75 Ohm coax and twisted pair? 

 

Based on the above links, there is absolutely a difference in construction and impedance, but what qualitative difference is there in actual listening?  I have no idea.

 

 

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33 minutes ago, Alexander said:

 

 

What if any effects would a typical coax 75ohm based interconnect cable have on the device(s) in is connected ti?  Not sure what if any impedance would exist on a shielded twisted pair equivalent.

 

 

 

 

Might have a look at wikipedia, I'm sure they'd have suitable information available.

 

For audio frequencies, the Chinese-made stuff in blister packs at Walmart is entirely sufficient.

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6 minutes ago, glens said:

For audio frequencies, the Chinese-made stuff in blister packs at Walmart is entirely sufficient.

 

ooooh!

 

can-of-worms.jpg

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12 minutes ago, glens said:

For audio frequencies, the Chinese-made stuff in blister packs at Walmart is entirely sufficient.

Agree, but the Walmart RCA cables are usually triple the price, or more compared to Monoprice coax. 

 

I'm thinking here of sub interconnects.  For a 1 meter audio interconnect I would want something better than the Walmart cables.

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I assumed moving-coil-to-preamp wasn't the consideration at hand.  High level sub(woofer) interconnects?  That's hardly even "audio" frequency!

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I'm still using the cheap cables that came with gear I bought in the early '70s. I've bought newer ones when I needed them but never anything exotic.

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A transmission line isn't a transmission line until it is at least 1/4 wavelength long. One-quarter wavelength at 20 kHz is 3.75 kilometers. As long as your interconnects are shorter than that, the concept of characteristic impedance doesn't apply.

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1 hour ago, wvu80 said:

I have the SVS Sound Path interconnects, twisted pair construction.  They have an impedance of 110 Ohms.

 

 

 

 

Ah, the twisted pair is 110 ohms, probably insignificant difference between the two then. Just curious about that. Fully aware of the construction of both kinds of cable.

 

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2 hours ago, glens said:

For audio frequencies, the Chinese-made stuff in blister packs at Walmart is entirely sufficient

I may agree when it comes to carrying the signal, but not quality of craftsmanship or build quality.  I have used the twisted pair of interconnects from Walmart, you can see green corrosion all the way through it, that and the fact that the connectors come loose, I would not spend the money. 

 

I have ran both RG59 and RG6 for interconnects with no issues.  I have ran the Monoprice rg 59 with no issues.  I mainly look for good shielded interconnects.

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The only way you will know if the cables work in your system is to try them in your system and evaluate the sonic results with your own ears.

 

I have listened to very expensive interconnects and speaker cables, cheap interconnects and speaker cables and everything in between.

 

To my ears, in my preferred systems, I have found that the very reasonably priced Belden 8402 (shielded 2-conductor) with Switchcraft RCAs and Canare L5-CFB (75 ohm coaxial) with Canare RCAs interconnects and Dueland 12ga speaker wire work great with my SE amps and HE speakers based systems. All use tinned conductors.

 

This combination has outperformed some very high priced stuff in my systems.

 

It also sounds much more like music than the cheap generic stuff.

 

This is just my opinion and YMMV. :)

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2 hours ago, Edgar said:

A transmission line isn't a transmission line until it is at least 1/4 wavelength long. One-quarter wavelength at 20 kHz is 3.75 kilometers. As long as your interconnects are shorter than that ...

Lol. Funny. 

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2 hours ago, Deang said:
4 hours ago, Edgar said:

A transmission line isn't a transmission line until it is at least 1/4 wavelength long. One-quarter wavelength at 20 kHz is 3.75 kilometers. As long as your interconnects are shorter than that ...

Lol. Funny. 

 

Shorter than  two and a half miles:blink:

 

I didn't measure, but I'm reasonably sure my interconnects are shorter than that.  I should be good to go.  :emotion-21:  :emotion-19:

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4 hours ago, Edgar said:

A transmission line isn't a transmission line until it is at least 1/4 wavelength long. One-quarter wavelength at 20 kHz is 3.75 kilometers. As long as your interconnects are shorter than that, the concept of characteristic impedance doesn't apply.

  Double check the math.

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Paul McGowen, President of PS Audio released this just a few hours ago.  Seems germane to the conversation, might add some food for thought.

 

 

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  This is using a velocity constant of one. Most propagation coefficients range from 0.75 - 0.8. But still long.

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21 minutes ago, Panelhead said:

  This is using a velocity constant of one. Most propagation coefficients range from 0.75 - 0.8. But still long.

 

Yeah, I know. But I figured that the absurdity of several kilometers (miles) compared to a couple of meters (feet) was sufficient to make the point.

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1 hour ago, Panelhead said:

  Double check the math.

 

Well, OK -- I used 3*10^8 meters per second for c; it's actually 299792458 meters per second. So 1/4 wavelength at 20 kHz is 3747.406725 meters. Assuming a worst-case velocity factor of 0.75, as suggested in a subsequent post, the quarter wavelength in the cable is 2810.554294 meters.

Edited by Edgar
Added missing word.

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Hmmm, I find a FULL wavelength of 20khz is only .17 inches. What am I missing here?

 

Bruce

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Radio (light) waves vs. audio (sound).  20kHz is a long radio wave.

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