Is 5m rca lead death

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billshurv

Member
Paid Member
2014-03-01 11:53 pm
Don't believe everything you read! Unless there is something badly wrong somewhere or you live next to Wrotham or Crystal Palace nothing nasty will happen. Use good quality screened coax and avoid any snake oily stuff. You think of all the systems you see with meaty mighty monster monoblocks next to the speakers, they often have 5m+ interconnects. You are running at 2VRMS out from the streamer so it'll be fine.

Or get the iPhone app for your NP30!
 
Don't believe everything you read! Unless there is something badly wrong somewhere or you live next to Wrotham or Crystal Palace nothing nasty will happen. Use good quality screened coax and avoid any snake oily stuff. You think of all the systems you see with meaty mighty monster monoblocks next to the speakers, they often have 5m+ interconnects. You are running at 2VRMS out from the streamer so it'll be fine.

Or get the iPhone app for your NP30!
Thanks billshurv
That is what I wanted to hear, I will get one from fleabay now.
Tha iphone app could be a problem as I dont have an iphone, I do have a tablet somewhere though.
Thanks
thyristor44
 
Hello
Problem is my cambridge audio np30 streamer is too far away for me to read,as its next to the amp.
I would like to bring the np30 nearer to me and use a 5m rca cable to go to the amp . I know its a horrible idea but is it deadly horrible.
Thanks
thyristor44

I ran 11m interconnects between my preamp and my active XOs in my last house ... with absolutely no problems. However, this was because:

* firstly, the preamp had low Zout (120 ohms) whilst the active XOs had high Zin (100K) - which meant a Zin / Zout ratio of over 800, and

* secondly, my preamp had an output stage which provided plenty of drive to run long cables.

So if your Zin / Zout ratio is OK (say > 100) and the streamer has a good output stage ... you won't have a problem.


Andy
 
Andy… you're pitching snake oil.

[1] "Firstly" is equivalent to "Secondly" … since if an amplifier has low impedance output and it amplifies, then it must also have substantial current drive. They're the same.

[2] The Zsource → Zsink ratio is only important in the sense that LO source impedance can drive LO or HI sinks, but HI source impedance can not drive LO sink impedance downwind equipment.

[2a] For instance, 600 Ω low impedance microphones can (and do) drive 600 Ω low impedance mixing board inputs … up to 50 meters or more, depending on the wire-gauge used to interconnect.

So… while your advice is fine, your attribution reasons are not.

Just saying
GoatGuy
 
[1] "Firstly" is equivalent to "Secondly" … since if an amplifier has low impedance output and it amplifies, then it must also have substantial current drive. They're the same.

Just saying
GoatGuy

Mmmm, you may well be factually correct with your statement, GG - but I know, for instance, that there are some preamps (which, by definition, "amplify") which have a wimpy output stage which has trouble driving long interconnects.

[2] The Zsource → Zsink ratio is only important in the sense that LO source impedance can drive LO or HI sinks, but HI source impedance can not drive LO sink impedance downwind equipment.

There was a TAS or Audiophile article in the early 80s which explained 2 things:
1) how cable capacitance affected the sound (high capacitance rolled off the highs), and
2) that the amount of roll-off was influenced by the Zout/Zin ratio (the lower the ratio ... the more capacitance influenced the amount of roll-off).


It made sense to me, so I continue to believe what the guy said. :)


Regards,

Andy
 
Andy… you're pitching snake oil.

[1] "Firstly" is equivalent to "Secondly" … since if an amplifier has low impedance output and it amplifies, then it must also have substantial current drive. They're the same.
low output impedance does not necessarily equate to adequate current capability.
[2] The Zsource → Zsink ratio is only important in the sense that LO source impedance can drive LO or HI sinks, but HI source impedance can not drive LO sink impedance downwind equipment.

[2a] For instance, 600 Ω low impedance microphones can (and do) drive 600 Ω low impedance mixing board inputs … up to 50 meters or more, depending on the wire-gauge used to interconnect.

So… while your advice is fine, your attribution reasons are not.

Just saying
GoatGuy
 
Mmmm, you may well be factually correct with your statement, GG - but I know, for instance, that there are some preamps (which, by definition, "amplify") which have a wimpy output stage which has trouble driving long interconnects.
The reason for not being able to drive the cable plus input stage is that low output impedance does not confer to ability to source adequate current to charge/discharge the capacitanes in the cable and the RF filtering usually fitted to input stages.
There was a TAS or Audiophile article in the early 80s which explained 2 things:
1) how cable capacitance affected the sound (high capacitance rolled off the highs), and
2) that the amount of roll-off was influenced by the Zout/Zin ratio (the lower the ratio ... the more capacitance influenced the amount of roll-off).


It made sense to me, so I continue to believe what the guy said. :)


Regards,

Andy
 
GoatGuy said:
[1] "Firstly" is equivalent to "Secondly" … since if an amplifier has low impedance output and it amplifies, then it must also have substantial current drive. They're the same.
No they are not the same. Output impedance and current drive capability are two quite different issues. However, any competently-designed audio source should be good enough at both to drive a 5m cable.

Let's assume a 300pF cable (5m at 60pF/m) plus 200pF of RF input filter at the load. So 500pF in total. Let's assume we need to drive 2V RMS into that at 20kHz. The peak signal current we need is given by
2 x sqrt(2) x 500e-12 x 20e3 x 2pi ~ 18e-5 = 0.18mA
(I hope that is right - did it in my head as the cat has settled on my lap so I can't get up and fetch my calculator)
In reality you will never get a full amplitude 20kHz with real music, but on the other hand you want to keep signal currents well below quiescent currents. So I think most competent output stages can provide enough current.

andyr said:
2) that the amount of roll-off was influenced by the Zout/Zin ratio (the lower the ratio ... the more capacitance influenced the amount of roll-off).
This is true, but only weakly so. Provided that Zin is much greater than Zout (almost always the case) then Zin is irrelevant.
 
Rather than "ratio" , I'd trust "absolute" value.

As in: if I'm worried about driving said 500pF (or any other real world load) , it will be significant whether preamp (driving end) out has, say, 100 ohms or 1000 ohms internal impedance; that the receiving end is 10k , 100k or 1M (we are varying "ratio" by a 100:1 factor ) is not that important.

As of internal impedance vs. current capability, a stage can lower internal impedance to a negligible amout by use of heavy feedback, that won't increase one iota the current sourcing or sinking capability.
 
Well now for the other side. With a 5 meter cable you can actually damage your sound system.

As far as circuit theory is concerned there is only resistance, capacitance and inductance to consider. Never mind things like skin effect. As to resistance a 5 meter cable of 24 gauge wire will add a bit more than 5 ohms to the output impedance of the preamp's output. This most likely will be around 100 ohms so the new source impedance will become 105 ohms. The input impedance is often 10,000 ohms although the standard is for 20,000 ohms. So the cable will add a loss of .0035 decibels. This increased resistance will now put your 3 db high frequency rolloff around 1,500,000 hertz. The inductance will put in a resonance around 8,000,000 hertz.

Then there is the issue of a source's output level. 2 volts RMS is probably more than enough to drive your amplifier into clipping. So you will be sending a level of typically .1 volts RMS for enough headroom and a comfortable listening level. So a with a typical output current of even the poorest audio chips of .01 amps that should be able to drive the input to well above clipping. It will actually not do the theoretical 100 volts as the power supply will limit the maximum signal well before that.

Simply put the cable will have a measurable impact that for almost all listeners, music and systems cannot be perceived.

However such a cable can cause significant damage to your system. With a 1 or 2 meter cable they are placed behind the equipment and shielded to some extent by the equipment. With a 15 meter cable that is not possible. In most applications this cable would even rest on the floor. That is where the problems come in. You can trip over the cord and cause your connected equipment to fall to the floor and get damaged. (Gotcha!) So be sure to either tie it off to something substantial or use cable clamps to the base board to provide strain (tripping) relief. :)
 
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billshurv

Member
Paid Member
2014-03-01 11:53 pm
Then there is the issue of a preamplifier's output level. 2 volts RMS is probably more than enough to drive your amplifier into clipping. So you will be sending a level of typically .1 volts RMS for enough headroom and a comfortable listening level. So a with a typical output current of even the poorest preamp chips of .01 amps that should be able to drive the input to well above clipping. It will actually not do the theoretical 100 volts as the power supply will limit the maximum signal well before that.

OP was only 5m and from source to preamp/integrated. :p

However such a cable can cause significant damage to your system. With a 1 or 2 meter cable they are placed behind the equipment and shielded to some extent by the equipment. With a 15 meter cable that is not possible. In most applications this cable would even rest on the floor. That is where the problems come in. You can trip over the cord and cause your connected equipment to fall to the floor and get damaged. (Gotcha!) So be sure to either tie it off to something substantial or use cable clamps to the base board to provide strain (tripping) relief. :)

Wise advice Ed :)
 

infinia

Member
2005-05-15 9:51 am
SoCal
plus the importance of S/N ratio due system gain distribution , claiming 2V signal over the amps input is nice but it's not what the OP has proposed.
doesn't the streamer supply the main signal attenuation, so "the amp" typical input voltage is many dB below the max. longer single ended cables carrying a smallish signal are indeed not a worry free zone. so many assumptions by a few posters here can lead to bad advice. I didn't read where "the amp" said it was "integrated" with the attenuator and whether is it cranked down to have 2V on the input?
 
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No they are not the same. Output impedance and current drive capability are two quite different issues. However, any competently-designed audio source should be good enough at both to drive a 5m cable.

We could choose either to agree or disagree on this one. Below the current-clipping point, the output of a stage offering some Z impedance will behave like a Z-limited power source. When whatever inherent (designed, or not-designed!) current limit is reached the effective Z of the source increases.

One can't have equations like [ P = IE and E = I R (or Z) ] and be able to squirrel out of I = E/Z without recognizing that current-limiting must change Z.

What I did not say (but which you did!) was that a competently designed amplifier - of some finite output impedance ZOUT must be able to source whatever current is needed for that Z over the maximum sustained output level, including whatever resistive, capacitive and inductive load is being designed for.

I really hadn't thought to include incompetently designed preamplifiers that nominally state 120 Ω ZOUT, but only so for a few dozen millivolts, then run out of juice and current-clip beyond that. I'm pretty old school, it seems.

Nice 'cat-on-the-lap' calculation, DF96.

GoatGuy
 
plus the importance of S/N ratio due system gain distribution , claiming 2V signal over the amps input is nice but it's not what the OP has proposed.
doesn't the streamer supply the main signal attenuation, so "the amp" typical input voltage is many dB below the max. longer single ended cables carrying a smallish signal are indeed not a worry free zone. so many assumptions by a few posters here can lead to bad advice. I didn't read where "the amp" said it was "integrated" with the attenuator and whether is it cranked down to have 2V on the input?

This is not a state of the art system. The standard today for an audio source is 2 Volts RMS peak output level. Many amplifiers are designed to provide maximum output at 1.4 Volts RMS. Then there is the actul signal to noise ratio. Figure about 20 dB for a typical bedroom, an average signal level of 70 dB and 30 dB for critical band selectivity. So 80 dB S/N will be the needed limit.

Now if you get into more advanced systems you certainly can get to issues with cables. But with the low impedance out and back in, the fairly short lengths and the limits of the implied components, there should not be any significant issues.
 
Well now for the other side. With a 5 meter cable you can actually damage your sound system.
...
However such a cable can cause significant damage to your system. With a 1 or 2 meter cable they are placed behind the equipment and shielded to some extent by the equipment. With a 15 meter cable that is not possible. In most applications this cable would even rest on the floor. That is where the problems come in. You can trip over the cord and cause your connected equipment to fall to the floor and get damaged. (Gotcha!) So be sure to either tie it off to something substantial or use cable clamps to the base board to provide strain (tripping) relief. :)

I was waiting for where this was going. :)
 
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