Re: Did he really say that???
Hi Jocko
I never measured on an XLR connector, but your result is close to what the industry believes it is. I assume the pin 1 versus "grounding" the connector housing itself also affects the impedance.
Assumed it is 100 ohm, it should work fine in a 100 ohm system. Would be funny to actually measure the transfer of such a system.
In addition, I do believe the transfer impedance of the whole connection is raised by the use of XLR connectors, which makes the effect of induced currents higher.
Let's stick to BNC.......all the best
Jocko Homo said:
Hi Jocko
I never measured on an XLR connector, but your result is close to what the industry believes it is. I assume the pin 1 versus "grounding" the connector housing itself also affects the impedance.
Assumed it is 100 ohm, it should work fine in a 100 ohm system. Would be funny to actually measure the transfer of such a system.
In addition, I do believe the transfer impedance of the whole connection is raised by the use of XLR connectors, which makes the effect of induced currents higher.
Let's stick to BNC.......all the best
Guido:
I measured between pins 2 & 3. Grounding the shield at one end to pin 1 will significantly lower the effective Z, as there is additonal capacitance between the shield and the conductors. This will result in a asymmetrical impedance, which I would assume would really cause a reflection problem. (Yet one more reason to sneer at AES/EBU.)
Transfer impedance probably is poor, and I have no way to measure it. At one time, I constructed something similar to Belden's SEED fixture to measure relative transfer impedance of coax cables.
(I tired to get Belden to lend me theirs......they about had a heart attack. But these are the same people who never once tried to sell cable to the second largest common carrier in the US.)
Jocko
I measured between pins 2 & 3. Grounding the shield at one end to pin 1 will significantly lower the effective Z, as there is additonal capacitance between the shield and the conductors. This will result in a asymmetrical impedance, which I would assume would really cause a reflection problem. (Yet one more reason to sneer at AES/EBU.)
Transfer impedance probably is poor, and I have no way to measure it. At one time, I constructed something similar to Belden's SEED fixture to measure relative transfer impedance of coax cables.
(I tired to get Belden to lend me theirs......they about had a heart attack. But these are the same people who never once tried to sell cable to the second largest common carrier in the US.)
Jocko
75 ohm BNC's rare?
75 ohm BNC’s are in fact quite common. The whole video world is using them. No problem to order them. There is a difference between 75 ohm and 50 ohm also regarding cable diameter. 75 ohm ones usually fits 6 mm RG59 and the 50 ohms ones the thinner RG58.
But this will probably solve your audiophile needs:
http://www.vandenhul.com/other/c-connec.htm#BNC
75 ohm BNC’s are in fact quite common. The whole video world is using them. No problem to order them. There is a difference between 75 ohm and 50 ohm also regarding cable diameter. 75 ohm ones usually fits 6 mm RG59 and the 50 ohms ones the thinner RG58.
But this will probably solve your audiophile needs:
An externally hosted image should be here but it was not working when we last tested it.
http://www.vandenhul.com/other/c-connec.htm#BNC
Farnell partnumber 151-841 for instance
Goto http://www.farnell.com/ and search for BNC
No they do not sell goldplated audiophile BNC stuff, but industrial stuff.
Regards
Goto http://www.farnell.com/ and search for BNC
No they do not sell goldplated audiophile BNC stuff, but industrial stuff.
Regards
The extra capacitance added by using a 50R connector is going to cause enough reflections to muck up the sound more than all the magical metallurgy used for the gold body can do to help it.
Which is probably zero anyway.
May look nice, but will not solve any of your problems.
But it is your gear......have at it.
Jocko
Which is probably zero anyway.
May look nice, but will not solve any of your problems.
But it is your gear......have at it.
Jocko
Jocko Homo said:The extra capacitance added by using a 50R connector is going to cause enough reflections to muck up the sound more than all the magical metallurgy used for the gold body can do to help it.
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Jocko
On a separate issue, is there any difference in the way BNC sockets are mounted. Two types: metal body on chasis, ground side to circuite secured on a tag by a nut with distance to center conductor variable OR insulated body, with centre pin to ground kept at fixed distance?
If so, why do pro gear and some instrument use the tag arrangement and also risk multiple grounds too?
Any of your measurements to enlighten us
fmak said:Jocko Homo said:The extra capacitance added by using a 50R connector is going to cause enough reflections to muck up the sound more than all the magical metallurgy used for the gold body can do to help it.
--------------------------------------------------
Jocko
On a separate issue, is there any difference in the way BNC sockets are mounted. Two types: metal body on chasis, ground side to circuite secured on a tag by a nut with distance to center conductor variable OR insulated body, with centre pin to ground kept at fixed distance?
If so, why do pro gear and some instrument use the tag arrangement and also risk multiple grounds too?
Any of your measurements to enlighten us
Hi
I'd suggest to directly contact the BNC to the chassis, then use a galavanic isolation ("digital" transformer like mini circuits T4-6T or Scientific conversion SC982-04) towards the PCB.
The advantage is:
- Low RF impedance towards the cabinet
- High impedance (except the shunt capacitance in the transformer) towards the PCB ground (eventually wrapping ferrite cores on the digital cable inside the cabinet - betweeen BNC and PCB - helps.
Hence any common mode current avoids to run through your electronics.
all the best
I'd suggest to directly contact the BNC to the chassis, then use a galavanic isolation ("digital" transformer like mini circuits T4-6T or Scientific conversion SC982-04) towards the PCB.
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Guido
In view of the earlier discussion about impedance matching, how is it that a panel mounted BNC with 15 cm of a twisted pair to a pcb with a transformer can maintain this matching? I have seen this on say dCS and other very high end equipment .
Fred
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Guido
In view of the earlier discussion about impedance matching, how is it that a panel mounted BNC with 15 cm of a twisted pair to a pcb with a transformer can maintain this matching? I have seen this on say dCS and other very high end equipment .
Fred
fmak said:
Fred, others
Twisted wire has a characteristic impedance of say 50 to 100 ohms (depending on wire type, twist ratio, such parameters). Ofcourse some mismatch may appear, but the consequences depend on the frequencies used as well.
In my clocks I use a maximum of 15 cm twisted wire. I measured the jitter at the end of that 15 cm and no differences could be observed, at least in the jitter values.
The effect of mismatching also depends on the sensibility of the source.
all the best
Late arrival, but still some things to say
Oh my, what a discussion...
Well, let's go on.
75 ohm BNCs are used for many years on professional video equipment.
They were not made because of cd-players or dacs.
50 ohm BNC plugs are (were) used on computer networks (10 BaseT), usually with RG-58 cable (50 ohms too).
I don't see any real advantage of gold-plating in the sound quality.
The only advantage I see is to prevent oxidation.
If the plugs were made of OFC copper, like many good cables, instead of cheap metal, then yes, you could probably get a better sound.
Really, it makes me think... why is it so important to have precisely a 75ohms plug, it it is soldered to a circuit and those line traces are not 75 ohms?
Anyway, I've seen plenty of 75ohms BNC plugs over the years (my father was a technician).
But if they are so hard to get, let me give you an idea, someone has talked about F-plugs.
They are very good, and they are 75 ohms.
What's more, the center pin is the cable's center pin.
Want more 75 ohms than this?
And if you look at the back of your tv, video and FM tuner you have 75 ohm plugs on them.
Not BNC, in fact, but 75 Ohm plugs.
Oh my, what a discussion...
Well, let's go on.
75 ohm BNCs are used for many years on professional video equipment.
They were not made because of cd-players or dacs.
50 ohm BNC plugs are (were) used on computer networks (10 BaseT), usually with RG-58 cable (50 ohms too).
I don't see any real advantage of gold-plating in the sound quality.
The only advantage I see is to prevent oxidation.
If the plugs were made of OFC copper, like many good cables, instead of cheap metal, then yes, you could probably get a better sound.
Really, it makes me think... why is it so important to have precisely a 75ohms plug, it it is soldered to a circuit and those line traces are not 75 ohms?
Anyway, I've seen plenty of 75ohms BNC plugs over the years (my father was a technician).
But if they are so hard to get, let me give you an idea, someone has talked about F-plugs.
They are very good, and they are 75 ohms.
What's more, the center pin is the cable's center pin.
Want more 75 ohms than this?
And if you look at the back of your tv, video and FM tuner you have 75 ohm plugs on them.
Not BNC, in fact, but 75 Ohm plugs.
Re: Late arrival, but still some things to say
dear Carlos,
Let me add some important details
The gold may prolong contact over a longer time. This is especially important for maintaining low transfer impedance of the interconnect, otherwise the induced voltage of external noise source will increase (the jitter)
A decently designed circuit IS 75 ohm. At least my SPDIF drivers and receivers are, they show over -35 dB at the VSWR measurement.
F plugs limit the variety of cables to be used (they require the - I think - 1 mm massive centre conductor.
The coaxial connectors used for television are dramatic, not only impedance wise.
To finish with: 50 ohm stems from industrial measurement equipment and has been adopted by the computer industry.
best regards,
carlosfm said:Oh my, what a discussion...
Well, let's go on.
75 ohm BNCs are used for many years on professional video equipment.
They were not made because of cd-players or dacs.
50 ohm BNC plugs are (were) used on computer networks (10 BaseT), usually with RG-58 cable (50 ohms too).
I don't see any real advantage of gold-plating in the sound quality.
The only advantage I see is to prevent oxidation.
If the plugs were made of OFC copper, like many good cables, instead of cheap metal, then yes, you could probably get a better sound.
Really, it makes me think... why is it so important to have precisely a 75ohms plug, it it is soldered to a circuit and those line traces are not 75 ohms?
Anyway, I've seen plenty of 75ohms BNC plugs over the years (my father was a tecnician).
But if they are so hard to get, let me give you an idea, someone has talked about F-plugs.
They are very good, and they are 75 ohms.
What's more, the center pin is the cable's center pin.
Want more 75 ohms than this?
And if you look at the back of your tv, video and FM tuner you have 75 ohm plugs on them.
Not BNC, in fact, but 75 Ohm plugs.
dear Carlos,
Let me add some important details
The gold may prolong contact over a longer time. This is especially important for maintaining low transfer impedance of the interconnect, otherwise the induced voltage of external noise source will increase (the jitter)
A decently designed circuit IS 75 ohm. At least my SPDIF drivers and receivers are, they show over -35 dB at the VSWR measurement.
F plugs limit the variety of cables to be used (they require the - I think - 1 mm massive centre conductor.
The coaxial connectors used for television are dramatic, not only impedance wise.
To finish with: 50 ohm stems from industrial measurement equipment and has been adopted by the computer industry.
best regards,
No, it comes from the radio electronics area. Mainly because vertical ground plane antennas were 50 ohms. The measurement industry has adopted it from this.
But if al this 75 ohm nick knack is a problem, why not use a 50 ohm system? 50 ohm drivers and receivers should be a snap for the serious DIY-selver.
But the F-connectors are a good solution. By using the accompanying 75 ohm cables you have also a low-cost low-loss high quality cable. It is available at any shop selling satellite-TV equipment.
Cheers
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