Hi Christophe,
A small correction.
The characteristic impedance of Ethernet TP cabling is 100 Ohm, not 75 Ohm. This spec can also be seen in your link. 😉
I realized my mistake yesterday night ( i was in trouble with my TV antenna et this time ;-) but it was too late to be corrected. Thanks for this correction.
I still have to experiment if correctly adapted on impedance both sides change anything on sound (HF reflexions).
I doubt, but worth a try 🙂
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Hi Christophe,
Interesting you terminate the screen at the source end, intuitively I would have done it the other way. Could you explain your logic for this.
thanks
mike
He he 🙂
- It is the point where there is the lowest impedance between hot signal wire and ground.
- A correctly designed amplifier (Like L.C. one) must have a low pass filter in order to limit slew-rate of the input signal. This filter helps to cure RMI/RFI on this side in the same time.
- If you preamplifier use global negative feedback, we have to protect its feedback path from EMI/RFI. We cannot set a low-pass filter this side without affecting preamp's stability and square waves accuracy.
Yes, it is counterintuitive. But think if you use a symmetrical line with trasfos on both sides. Or if this your Speaker cable as well ;-)
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Tip:
Each time we look at a wire, we have to think 'currents' and their effects (magnetic fields etc.)
Current is what makes an electron to jump from an atom of coper to the next one, transmitting our beloved signal.
Across a perfect wire, their is no voltages.
🙂
Each time we look at a wire, we have to think 'currents' and their effects (magnetic fields etc.)
Current is what makes an electron to jump from an atom of coper to the next one, transmitting our beloved signal.
Across a perfect wire, their is no voltages.
🙂
Hi LC, just fire up FO today with simple PSU share both channels. Measured DC offset for channels are 4.2mV and 16mV respectively. Does that sound ok to you?
Quan
Quan
Hi Quan
With input shorted everything in between +/-10 mV is OK.
Otherwise look to the last chapter in user's manual and correct it to zero. 😉
I recently commented on local Serbian forum that there is a special cable suitable for internal wiring of the input connector that I use:
Belden 1508A - shielded twisted pair, not very thick, easy to lay inside enclosure, tinned copper conductors, polyolefin insulation, PVC jacket, Beldfoil shield (100% coverage), capacitance conductor/conductor 31pF. Third conductor is uninsulated and touching the shield so it is very easy to connect shield to ground (at one side, of course, and preferably, like Esperado suggests, at preamp side).
This is US product but I found it from a person selling it here in Serbia. Should be possible to find it elsewhere?
Belden 1508A - shielded twisted pair, not very thick, easy to lay inside enclosure, tinned copper conductors, polyolefin insulation, PVC jacket, Beldfoil shield (100% coverage), capacitance conductor/conductor 31pF. Third conductor is uninsulated and touching the shield so it is very easy to connect shield to ground (at one side, of course, and preferably, like Esperado suggests, at preamp side).
This is US product but I found it from a person selling it here in Serbia. Should be possible to find it elsewhere?
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Yes looks good and found at www.canford.co.uk but data there says conductor is 7x0.2 tinned copper and not one solid conductor. So if one prefer one solid core, can you describe the core in the one you have.
At AWG24 it does not matter anymore if the cable is multi stranded or not. Solid core is preferred. The audible skin effect is beyond 20 kHz.
I would prefer AWG26 solid core.
Exactly. This cable is stranded because similar Belden product is used by BBC for mixing desk patching, so multi stranding allows cable to be manipulated more vigorously and frequently.
Sonically i would still prefer thin solid core for home use. For studio where flexibility and reliability is more important, multistranded is the way to go.
I am unsure if shielding is necessary for short cables. Lets say up to 2 meters which is really maximum someone would use at home.
In studio where they use several 10 of meters for cables, shielding is a must.
It's right that twisted pair is the best for the sound (as interconnect) but if thin solid core conductors are used for internal wiring (or interconnecting) there is a chance that if you bend the conductors (and that is unavoidable) there will be some cracks on the surface of the copper conductor. It is not only bad for the reliability of the cable but also for the quality of the reproduced sound. It would be necessary that small cross-section copper conductor is tinned for such applications and it will be very difficult to find tinned and insulated copper conductor suitable for the job. Very pure copper is the worst in that respect (if it is not tinned) as it will crack very easily.
This is not only explained in some texts by Ben Duncan but is also my personal experience.
This is not only explained in some texts by Ben Duncan but is also my personal experience.
I used solid core Cat 5 or Cat 6 in for all my audio - internal, interconnects & speaker leads - for the last 10 years and I never once had any problem of any kind so I can't take this theoretical problem too seriously.
Solid core just sounds better to me than stranded
Solid core just sounds better to me than stranded
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An other point is the strength and stiffness of the assembly.
On stages, and high impedance guitar cables, you can clearly hear noise generated by any movement or stepping on the (high impedance) guitars cables.
This is due to the variation of their capacitance with deformation. I believe, far away beyond the signal level, acoustic pressure can have a similar effect. Yes, cables can be microphonic 🙂
I personally agree with the preferences for solid core. One can believe the millions of imperfect contacts between the strands of a cable and diode effects with oxidation at their surface can generate some king of grainy sound ?
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Also does a signal split to 10 strands or more arrive exactly same time (uS) in other end before they mix together (at all freqs) when presented to what Esparado mention above. If such thinking is reality and true such a cable should only be used to music production for making a effect on a track, and not on reproducing where effects unvelcome if we want to hear the intended art. Above is just thoughts no proof or science, please take as is.
No, Byrtt, that's not the case. From the QED Genesis Report Pt.2:
The first question one needs to ask is “How is the signal transferred from one end of the cable to the other?” It is easy to imagine that the free electrons at the sending end of the cable travel at an extremely high velocity to the receiving end. This seems plausible until you measure the speed at which electrons travel in a conductor, this speed is called the drift velocity.
For a 1 metre interconnect it takes the free electrons around 100 seconds to travel from one end to the other. This is a significant time and clearly we do not wait that long for music or video to appear, so another transmission mechanism must be occurring.
Thankfully a Scottish mathematician and theoretical physicist named James Maxwell (1832-1879) provided an answer through his work on electromagnetic waves. Signals do in fact travel down cables as an electromagnetic wave and this wave does travel at a very high velocity. If the metal conductor were perfect virtually all the energy would be transferred from one end of the cable to the other in the electric and magnetic fields around the conductor.