Ok, doing some more search , I find the impencence values of my CD transport and DAC which are as under .
1) CD player : at RCA output , Impedence is 100 ohm. But I am taking digital output from this CD player , so using it only as transport
2) DAC : At RCA output , Impedence is 74 ohm
3) Preamp : taking analog signal from the DAC , input Impedence is 50 K Ohm ,
output Impedence is 560 Ohm
4) Tube Amp : Input Impedence is 150 K Ohm
JMF , please , your comments , suggestions will be most appreciated .
Thanks
1) CD player : at RCA output , Impedence is 100 ohm. But I am taking digital output from this CD player , so using it only as transport
2) DAC : At RCA output , Impedence is 74 ohm
3) Preamp : taking analog signal from the DAC , input Impedence is 50 K Ohm ,
output Impedence is 560 Ohm
4) Tube Amp : Input Impedence is 150 K Ohm
JMF , please , your comments , suggestions will be most appreciated .
Thanks
Ok, let me see if I understood you well.
Currently you have a: CD transport plus DAC > Preamp > tube amp ?
And your new cable would go between preamp and tube amp?
If so, don´t worry, most any decent cable will do.
Just suppose your 7 meter long cable (IC if you wish) has very average 100pF per meter; then 7 meters would mean some 700 pF.
Add to that some 100pF to account for the power amp input capacitance (it will definitely have *some* capacitance, 100pF is not a bad estimate)
So we can count on some 800 pF loading your preamp output.
The -3dB frequency will be that at which those 800pF show an around 560 ohm impedance (stated preamp out impedance) but that would be a heavy load; to play it safe and nice let´s do our Math calculating when those 800pF reach 10X higher (so they are not a significant load for the preamp), in this case 5600 ohms.
Let´s use a nice online calculator: RC pad corner frequency upper and lower cutoff frequency calculation filter calculate time constant tau RC voltage power calculator capacitance resistance - sengpielaudio Sengpiel Berlin
There´s many others of course, but I found this one straight and to the point, so ....
working with 5600 ohms and 800 pF, we find that the 800pF cable will be a comfortable " I don´t notice you are there" preamp load up to: 35 kHz, and not *really* become annoying until 350 kHz.
And that with an average quality 100pF/meter basic cable
In a nutshell: in your configuration, most any reasonable cable/IC will work fine; you can search to improve quality to, say, 50 pF per meter or 350pF total; beyond that it isn´t worth it.
And no matter what cable/IC you use, you will *still* have those around 100pF at the amp input.
If anything, give some extra thought to quality connectors, making certain that soldering is good, etc. , but no need to overthink it nor to overspend because, simply, "you don´t need to"
Currently you have a: CD transport plus DAC > Preamp > tube amp ?
And your new cable would go between preamp and tube amp?
If so, don´t worry, most any decent cable will do.
Just suppose your 7 meter long cable (IC if you wish) has very average 100pF per meter; then 7 meters would mean some 700 pF.
Add to that some 100pF to account for the power amp input capacitance (it will definitely have *some* capacitance, 100pF is not a bad estimate)
So we can count on some 800 pF loading your preamp output.
The -3dB frequency will be that at which those 800pF show an around 560 ohm impedance (stated preamp out impedance) but that would be a heavy load; to play it safe and nice let´s do our Math calculating when those 800pF reach 10X higher (so they are not a significant load for the preamp), in this case 5600 ohms.
Let´s use a nice online calculator: RC pad corner frequency upper and lower cutoff frequency calculation filter calculate time constant tau RC voltage power calculator capacitance resistance - sengpielaudio Sengpiel Berlin
There´s many others of course, but I found this one straight and to the point, so ....
working with 5600 ohms and 800 pF, we find that the 800pF cable will be a comfortable " I don´t notice you are there" preamp load up to: 35 kHz, and not *really* become annoying until 350 kHz.
And that with an average quality 100pF/meter basic cable
In a nutshell: in your configuration, most any reasonable cable/IC will work fine; you can search to improve quality to, say, 50 pF per meter or 350pF total; beyond that it isn´t worth it.
And no matter what cable/IC you use, you will *still* have those around 100pF at the amp input.
If anything, give some extra thought to quality connectors, making certain that soldering is good, etc. , but no need to overthink it nor to overspend because, simply, "you don´t need to"
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Use the formula:
F-3dB = 1 / {2 Pi R C}
for a source impedance of 560ohms and a load capacitance of 800pF
you will get F-3dB = 355kHz. (that's what JMF was describing).
If there was 1nF of RF filtering capacitance in the load, then the total capacitance would be <=1n7F and F-3dB would be > 167kHz
F-3dB = 1 / {2 Pi R C}
for a source impedance of 560ohms and a load capacitance of 800pF
you will get F-3dB = 355kHz. (that's what JMF was describing).
If there was 1nF of RF filtering capacitance in the load, then the total capacitance would be <=1n7F and F-3dB would be > 167kHz
Thank you DF96 and AndrewT,
Much of the mystery in selection of cable is now clear to me. Feel happy that I put up my problem here , as it helped me stop my chase for "hi-end" IC several times more costly.
Now I shortlist following cables for me ( All are within my budget ) :
1. Neotech NEI 3002 OCCx2 conductors twisted pair, Double Shielded, cotton fiber, OD 10.5 mm , $9 /FT
2. Neotech NEI 3003 III, CO-EX, OCC double shielded,paper textile, OD 8.5 mm,
$5.8 /FT
3. Neotech NEI 3001 III , OCCx 4 conductors, twisted pair, PE air tubes , teflon tape,
paper textile, ,Double shielded, OD 10.5 mm, $14.5 / FT
4. Furutech U-P 2.1 , 19AWG x2 OCC conductors, , twisted pair, double shielded,
OD 8.0 mm, $12 / FT
RCA: I will go for good quality Furutech or Neotech Rhodium plated RCA .
Like you said , CO-EX cable is fine, but i feel concerned for a longer length, and that my cable will pass through a aluminum cable duct under the floor to cover about 4 meter distance.
One criterion in building this new cable for me is also to get some improvement over my existing Cardas Hexlink Golden Five RCA of 5 meter length.
Can I ask you What would be your pick ?
Thanks for your efforts and lots of help.
Much of the mystery in selection of cable is now clear to me. Feel happy that I put up my problem here , as it helped me stop my chase for "hi-end" IC several times more costly.
Now I shortlist following cables for me ( All are within my budget ) :
1. Neotech NEI 3002 OCCx2 conductors twisted pair, Double Shielded, cotton fiber, OD 10.5 mm , $9 /FT
2. Neotech NEI 3003 III, CO-EX, OCC double shielded,paper textile, OD 8.5 mm,
$5.8 /FT
3. Neotech NEI 3001 III , OCCx 4 conductors, twisted pair, PE air tubes , teflon tape,
paper textile, ,Double shielded, OD 10.5 mm, $14.5 / FT
4. Furutech U-P 2.1 , 19AWG x2 OCC conductors, , twisted pair, double shielded,
OD 8.0 mm, $12 / FT
RCA: I will go for good quality Furutech or Neotech Rhodium plated RCA .
Like you said , CO-EX cable is fine, but i feel concerned for a longer length, and that my cable will pass through a aluminum cable duct under the floor to cover about 4 meter distance.
One criterion in building this new cable for me is also to get some improvement over my existing Cardas Hexlink Golden Five RCA of 5 meter length.
Can I ask you What would be your pick ?
Thanks for your efforts and lots of help.
If you go for Balanced impedance connection, then you don't use RCA/Phono connectors.
If you go for unbalanced, then use a good quality coaxial.
I do not understand why you are only listing very expensive versions and most are STP .
What's wrong with going to someone like Blue jeans who will sell you a ready terminated cable, either balanced with a 3pin connector or unbalanced with a 2pin connector at a fraction of the costs you are listing for bare cable?
If you go for unbalanced, then use a good quality coaxial.
I do not understand why you are only listing very expensive versions and most are STP .
What's wrong with going to someone like Blue jeans who will sell you a ready terminated cable, either balanced with a 3pin connector or unbalanced with a 2pin connector at a fraction of the costs you are listing for bare cable?
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But you still seem to be going for expensive cables. Why? You clearly have not really taken on board what we are saying.Radni said:
If the length is too long for coax then the solution is to use twisted pair in a balanced configuration. Twisted pair itself has no special merits in an unbalanced connection, just as coax has no merits in a balanced connection.
You have no choice, for a long cable unbalanced use coaxial.
Find one that has good coverage of a braided screen with lots of copper crossectional area.
Low resistance is a good clue to copper content.
Stay with 75ohms rather than 50ohms for lower capacitance.
Double braided, or braid+foil is usually better than single braid and all of these are better than a lapped screen. Do not use lapped.
Find one that has good coverage of a braided screen with lots of copper crossectional area.
Low resistance is a good clue to copper content.
Stay with 75ohms rather than 50ohms for lower capacitance.
Double braided, or braid+foil is usually better than single braid and all of these are better than a lapped screen. Do not use lapped.
I would not order that.
I cannot see nei 3003 III co-ex
Is that a different version from nei 3003 III
This is not a double braided screen.
It is a single braid and some conductive inner screen. I don't trust that.
Copper foil is very good, or aluminised plastic foil is adequately good.
Either should be overlaid with a braided copper screen.
I cannot see nei 3003 III co-ex
Is that a different version from nei 3003 III
This is not a double braided screen.
It is a single braid and some conductive inner screen. I don't trust that.
Copper foil is very good, or aluminised plastic foil is adequately good.
Either should be overlaid with a braided copper screen.
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It baffles me why people seem willing to pay far more for an audio cable than an RF cable. The latter is a far more exacting application, yet good cable is available at reasonable prices (of the order of £1/m i.e. 30p (35c?) per ft). Maybe most people buying RF cable actually know something about RF?
AndrewT,
Here is the link to NEI 3003 III coex
Neotech NEI-3003 MK III, Sonic Craft
At least they say it is coex. Can you please check it out ?
Here is the link to NEI 3003 III coex
Neotech NEI-3003 MK III, Sonic Craft
At least they say it is coex. Can you please check it out ?
Well, it does say:
Maybe our friend Radni feels somewhat insecure about his Audio System and finds comfort in high prices? ..... or hype?
Please understand me, I´m not saying that Neotech cable is *horrible* and they hide that ugly factor, far from that, but simply that their parameters must not be any better than serious manufacturer ones, which to boot sell **good** cable for the real price.
And *sometimes* , not necessarily here because this one looks like plain vanilla Coax, but often in wildly twisted or knitted speaker cables, "cool features" actually HURT cable performance, by increasing resistance/capacitance/inductance/you-name-it.
In any case, looks like Radni wants to spend some extra money on his cable (did I hear 800$?), logged in to get confirmation and unfortunately met a bunch of hard headed Pros who are actually guided by performance and not price or hype.
Oh well.
Radni, do as you wish and enjoy, what can I (we) tell you?
Sorry, it doesn´t work that way.
which I assume is "coex" , but besides that, they post NO parameter whatsoever, so I wouldn´t buy it either.
Maybe our friend Radni feels somewhat insecure about his Audio System and finds comfort in high prices? ..... or hype?
Please understand me, I´m not saying that Neotech cable is *horrible* and they hide that ugly factor, far from that, but simply that their parameters must not be any better than serious manufacturer ones, which to boot sell **good** cable for the real price.
And *sometimes* , not necessarily here because this one looks like plain vanilla Coax, but often in wildly twisted or knitted speaker cables, "cool features" actually HURT cable performance, by increasing resistance/capacitance/inductance/you-name-it.
In any case, looks like Radni wants to spend some extra money on his cable (did I hear 800$?), logged in to get confirmation and unfortunately met a bunch of hard headed Pros who are actually guided by performance and not price or hype.
Oh well.
Radni, do as you wish and enjoy, what can I (we) tell you?
Sorry, it doesn´t work that way.
I note that Neotech put the word " "value" " in quotes, which is what people sometimes do when they know it is the wrong word. It is the wrong word, as multiple dollars per ft is not 'value'.
Why not buy proper cable from a proper cable maker like Belden, or even a sensible audio cable company like Blue Jeans (who seem to understand electricity)?
Why not buy proper cable from a proper cable maker like Belden, or even a sensible audio cable company like Blue Jeans (who seem to understand electricity)?
I have no dog in this fight but I was wondering about this: COAXIAL CABLE RG 400 CERTIFIED from Aircraft Spruce
Specs are here: RG400 Cable | High Frequency Coax with Solid Dielectric & FEP Jacket
Specs are here: RG400 Cable | High Frequency Coax with Solid Dielectric & FEP Jacket
I decided to order one pair of 7 mt. cable from Blue Jeans , which costs only a fraction of what I would have spent on so called "conventional" audio cables.
I will also be able to do A-B test against my current Cardas cable.
I was amazed to see the details in specs of Belden Coex on site , though much beyond my understanding . But I could see vital details on capacitance , RF , impedance , coductor, shield , insulation , also cross sections and thickness of them, etc. Only thing it does not say is about quality or purity of copper conductor and shield: according to me something should have been stated. But some FMs here say , it should not matter , any good copper conductor is fine, so may be not so important. In one of my earlier posts I did say audio cable mfrs are not forthcoming with technical details of their cables, now with what I see under Belden specs are very reveling to me.
If I am happy with Belden Coex cable , I am sure to drastically change my thinking on cables. I look forward to it.
Thanks folks.
I will also be able to do A-B test against my current Cardas cable.
I was amazed to see the details in specs of Belden Coex on site , though much beyond my understanding . But I could see vital details on capacitance , RF , impedance , coductor, shield , insulation , also cross sections and thickness of them, etc. Only thing it does not say is about quality or purity of copper conductor and shield: according to me something should have been stated. But some FMs here say , it should not matter , any good copper conductor is fine, so may be not so important. In one of my earlier posts I did say audio cable mfrs are not forthcoming with technical details of their cables, now with what I see under Belden specs are very reveling to me.
If I am happy with Belden Coex cable , I am sure to drastically change my thinking on cables. I look forward to it.
Thanks folks.
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