Hello. I`m looking at building a breakout-box in order to provide a solution for users of a popular speaker audio system. The amplifier uses a 15 pin D-sub-miniature cable to transmit power and signal lines back and fourth through a kind of preamp system..
There is a line of the dsub cable for a dedicated power return(ground), and a line for a dedicated signal return(ground). The dedicated signal return/ground is a shared return for all system audio signals(2).
I am concerned, that if i chassis(panel) mount my bnc/rca pass-through jacks(couplers), and panel mount my power jack, and panel mount the dsub coupler, to the shielded chassis, that since the jacks body, I understand, carries the ground/return/shield, in these single ended interconnects, that when mounted the ground-return for signal lines, and the ground-return for the power line will meet, through the chassis shielding and cause a problem.
I am an electronics newbie, who just likes to fix things and try to help out here. I'm concerned that because of this design; where there are dedicated power return-ground lines, and signal return-ground lines, that having the ground-returns connected like this is an issue..
Hopefully someone can help me out here, or offer me some kind of advice for making such a solution and regarding this grounding issue... I'm fairly new to this sort of understanding.. Thanks, for your time and attention. I'm looking forward to kind and helpful response(s). Have a good day fellows.
(1)
Here is a link to what a dsub cable is
https://en.wikipedia.org/wiki/D-subminiature
(2)
Discrete signal and power return lines as described here
Logitech Z-2300 Remote Control Pod Disassembly – blog.jseaber.com
There is a line of the dsub cable for a dedicated power return(ground), and a line for a dedicated signal return(ground). The dedicated signal return/ground is a shared return for all system audio signals(2).
I am concerned, that if i chassis(panel) mount my bnc/rca pass-through jacks(couplers), and panel mount my power jack, and panel mount the dsub coupler, to the shielded chassis, that since the jacks body, I understand, carries the ground/return/shield, in these single ended interconnects, that when mounted the ground-return for signal lines, and the ground-return for the power line will meet, through the chassis shielding and cause a problem.
I am an electronics newbie, who just likes to fix things and try to help out here. I'm concerned that because of this design; where there are dedicated power return-ground lines, and signal return-ground lines, that having the ground-returns connected like this is an issue..
Hopefully someone can help me out here, or offer me some kind of advice for making such a solution and regarding this grounding issue... I'm fairly new to this sort of understanding.. Thanks, for your time and attention. I'm looking forward to kind and helpful response(s). Have a good day fellows.
(1)
Here is a link to what a dsub cable is
https://en.wikipedia.org/wiki/D-subminiature
(2)
Discrete signal and power return lines as described here
Logitech Z-2300 Remote Control Pod Disassembly – blog.jseaber.com
Proper safety practice is to connect the AC line safety ground (green wire) directly to the chassis,
immediately after it enters the chassis. There are no exceptions to this safety rule with a metal chassis.
An external DC power supply or wall wart could be used instead, with less chance for noise problems.
Last edited:
Thanks for the responses
Thanks for making the responses gentlemen, but as far as i can tell the responses mean slightly different things, but have some shared considerations, correct me if i'm wrong. Heh, and I'm not versed enough, to know what route to follow. But thanks for the contributions. Maybe i can see some re-affirmation and agreement, and some more understanding to help me decide on a method, if I share more of my plans.
I was hoping to use the same panel to mount the rca`s and power ground, and have them both combine for the chassis/shield, but it would seem like, it`s suggested, by the forum community respondents, that I ground only one of these two connections. Like the rca signal jacks, or ground a coaxial power jack(on the inside immediately(should be covered by the panel mounting connection to the shield, and a dedicated wire))..
But wouldn't have the foggiest which route to go with.
Originally I was thinking of a conductive metal case, or a foil lined wooden box. If going with the wooden box, it might be made shielded with foil and a layer conductive paint, in the same fashion as used for the internals of electric guitars, but with two panels affixed, one for the db15 input/output coupler, which would connect the ground to the amplifier, and one for the bnc/rca input/output and power connections, which would carry the ground to that point. I planned to make the connection from the db15 to the rca/bnc via a custom dsub to bnc cable in the middle, and plugging that cable inside the box to the coupler jacks on either side. I was looking at Canare panel mount couplers, as the jacks(3), and crimping with Belden double bubble bnc connectors to the dsub cable. I might have even kept the power jack as a bnc, but i was looking at the power jacks too. However, i guess this is likely; no longer a good option..
Also, Gus, wouldn't an unisolated rca mean that the rca`s share the ground-return with the chassis shield, then? And that your advice means that I should keep the power ground, in a coaxial power cable, away from the chassis, to keep the signal ground clean? Then this would go contrary to my hope of just plugging them into the same panel and sharing the return/shielding..
If I follow Raymas method, and keep the returns separate too, wouldn't the ground be power the be only return connected to the shield, and i'd have to have isolate the rca jacks? How can I shield the jack connections then, if they are isolated..? I was hoping to use something like Canare passthrough jacks listed below, on a shielded panel, connected to the main box. I guess i was hoping for a fix which was too easy..
I could also just make the power connection inside the box, and avoid the standby power connection, which is just a switch, since the system has a switch on the back, which is rougher.. But then; I'm not sure, if the dsub return connection line, along it's shield and connector, is supposed to carry the power ground, possibly, then it will have mixed the power and the signal return again... unless we use an isolated rca? I don't think the blog i references lists which ground-return the dsub carries along it's shield.. If the dsub shield carries the ground return, I suspect then i'll mount the power receptacle on the same panel as the db15 dsub-miniature coupler, and have them share the shield/return. I was looking at the very expensive (relativly), switchcraft panel mount couplers, for power jacks and the dsub coupler, they seem to have a nice panel mount system.
I guess, i come all this way, no easy way out for me eh fellas? Cause i can't combine them and expect a good result? "It looks like they run a separate power ground, which is good practice." Also, Gusser the design of the z-2300 results is pretty.. alright, I suspect, mean not perfect, but pretty good. It supposedly nets a SNR of around 107, in class A mode. For a computer speaker amplifier, I think it's the "best", at least electronics wise up to that point in computer speaker history
. This is one reason I am posting here, not just for myself, but because this is a popular and historically available, and still very relevant, platform, imo.. And most of the units are nearly free on ebay, sometimes just pay the shipping'. It`s easy to connect some two way satellites, or some newer full range drivers, like the Dayton rs-100. Most computer speakers amps, I understand, have an snr or dynamic range around 90, or 88.. (but I might be mistaken in this). Anyhow, i have been working on this solution for awhile. Also Rayma, the z-2300 has a relatively large internal Toroidal transformer. I was thinking of transplanting it, and the rest of the amp into an amplifier case, with a divider between some of the amp, and the transformer, or putting that part in a separate box, however, some of the power section, filter capacitors, I understand is sharing a board with signal handling sections..
I hope to hear from the community again, to re-affirm some direction for me and the project.
(3)
BCJ-JR
https://www.bhphotovideo.com/c/product/937474-REG/canare_bcj_jr_75_bnc_to.html
Canare Corp.: 75 ohm BNC Connectors: 75 ohm BNC Standoff Receptacles(BCJ Series)
RJ-BCJRUD
http://www.canare.com/UploadedDocuments/FlushMountBulkheadReceptacles.pdf
Thanks for making the responses gentlemen, but as far as i can tell the responses mean slightly different things, but have some shared considerations, correct me if i'm wrong. Heh, and I'm not versed enough, to know what route to follow. But thanks for the contributions. Maybe i can see some re-affirmation and agreement, and some more understanding to help me decide on a method, if I share more of my plans.
I was hoping to use the same panel to mount the rca`s and power ground, and have them both combine for the chassis/shield, but it would seem like, it`s suggested, by the forum community respondents, that I ground only one of these two connections. Like the rca signal jacks, or ground a coaxial power jack(on the inside immediately(should be covered by the panel mounting connection to the shield, and a dedicated wire))..
But wouldn't have the foggiest which route to go with.
Originally I was thinking of a conductive metal case, or a foil lined wooden box. If going with the wooden box, it might be made shielded with foil and a layer conductive paint, in the same fashion as used for the internals of electric guitars, but with two panels affixed, one for the db15 input/output coupler, which would connect the ground to the amplifier, and one for the bnc/rca input/output and power connections, which would carry the ground to that point. I planned to make the connection from the db15 to the rca/bnc via a custom dsub to bnc cable in the middle, and plugging that cable inside the box to the coupler jacks on either side. I was looking at Canare panel mount couplers, as the jacks(3), and crimping with Belden double bubble bnc connectors to the dsub cable. I might have even kept the power jack as a bnc, but i was looking at the power jacks too. However, i guess this is likely; no longer a good option..
Also, Gus, wouldn't an unisolated rca mean that the rca`s share the ground-return with the chassis shield, then? And that your advice means that I should keep the power ground, in a coaxial power cable, away from the chassis, to keep the signal ground clean? Then this would go contrary to my hope of just plugging them into the same panel and sharing the return/shielding..
If I follow Raymas method, and keep the returns separate too, wouldn't the ground be power the be only return connected to the shield, and i'd have to have isolate the rca jacks? How can I shield the jack connections then, if they are isolated..? I was hoping to use something like Canare passthrough jacks listed below, on a shielded panel, connected to the main box. I guess i was hoping for a fix which was too easy..
I could also just make the power connection inside the box, and avoid the standby power connection, which is just a switch, since the system has a switch on the back, which is rougher.. But then; I'm not sure, if the dsub return connection line, along it's shield and connector, is supposed to carry the power ground, possibly, then it will have mixed the power and the signal return again... unless we use an isolated rca? I don't think the blog i references lists which ground-return the dsub carries along it's shield.. If the dsub shield carries the ground return, I suspect then i'll mount the power receptacle on the same panel as the db15 dsub-miniature coupler, and have them share the shield/return. I was looking at the very expensive (relativly), switchcraft panel mount couplers, for power jacks and the dsub coupler, they seem to have a nice panel mount system.
I guess, i come all this way, no easy way out for me eh fellas? Cause i can't combine them and expect a good result? "It looks like they run a separate power ground, which is good practice." Also, Gusser the design of the z-2300 results is pretty.. alright, I suspect, mean not perfect, but pretty good. It supposedly nets a SNR of around 107, in class A mode. For a computer speaker amplifier, I think it's the "best", at least electronics wise up to that point in computer speaker history
. This is one reason I am posting here, not just for myself, but because this is a popular and historically available, and still very relevant, platform, imo.. And most of the units are nearly free on ebay, sometimes just pay the shipping'. It`s easy to connect some two way satellites, or some newer full range drivers, like the Dayton rs-100. Most computer speakers amps, I understand, have an snr or dynamic range around 90, or 88.. (but I might be mistaken in this). Anyhow, i have been working on this solution for awhile. Also Rayma, the z-2300 has a relatively large internal Toroidal transformer. I was thinking of transplanting it, and the rest of the amp into an amplifier case, with a divider between some of the amp, and the transformer, or putting that part in a separate box, however, some of the power section, filter capacitors, I understand is sharing a board with signal handling sections..I hope to hear from the community again, to re-affirm some direction for me and the project.
(3)
BCJ-JR
https://www.bhphotovideo.com/c/product/937474-REG/canare_bcj_jr_75_bnc_to.html
Canare Corp.: 75 ohm BNC Connectors: 75 ohm BNC Standoff Receptacles(BCJ Series)
RJ-BCJRUD
http://www.canare.com/UploadedDocuments/FlushMountBulkheadReceptacles.pdf
Last edited:
Project likely going power ground now..
We`ll, I understand now that these two grounds are likely kept separate, however, I am still not sure which ground to use for the breakout box chassis shield. This diagram(4), seems to show the dsub cable shield as being the signal ground so then shouldn't I also have the breakout box be signal ground? And in this forum(5), also, I understand it contents that common ground is case ground, which it states as also signal ground(audio ground).
I suppose like rymans advice, the power ground would be the most direct route to ground? It just feels weird to me, if I'm interpreting the diagram correctly, to go from using signal ground convention; for the cable shield, to using power ground for the chassis shield. Why break the continuity of design? And why would Logitech apply the signal ground to the db15 cable shield; when the power ground is the most direct route to ground, if they had no reason for it? Or what could be their reason, and would the reason also apply to the similar application of the breakout-box chassis shield?
Either way, I understand I should run a direct lead from the ground connector, to the chassis shield.. likely a line soldered to the connector, and possibly screwed and soldered to the shield. Will the size of the breakout box chassis, and shielding, have an impact on the projects system performance? Maybe less so coming through the power ground?
As it is right now, I think I'm going with the power route, even if this is counter to logitech's decision on the vga cable shield.. Thanks again diyAudio community for your attention to the matter and contributions.
(4)
http://blog.jseaber.com/wp-content/uploads/2010/04/remoteV100.pdf
(5)
"WA1 & WA2 |Black (big)| Are common or Ground.. Also Audio Ground | CASE |"
post 9
http://www.electro-tech-online.com/threads/logitech-z-2300-controller.100515/]
Logitech Z 2300 Controller | Electronics Forum (Circuits, Projects and Microcontrollers)
We`ll, I understand now that these two grounds are likely kept separate, however, I am still not sure which ground to use for the breakout box chassis shield. This diagram(4), seems to show the dsub cable shield as being the signal ground so then shouldn't I also have the breakout box be signal ground? And in this forum(5), also, I understand it contents that common ground is case ground, which it states as also signal ground(audio ground).
I suppose like rymans advice, the power ground would be the most direct route to ground? It just feels weird to me, if I'm interpreting the diagram correctly, to go from using signal ground convention; for the cable shield, to using power ground for the chassis shield. Why break the continuity of design? And why would Logitech apply the signal ground to the db15 cable shield; when the power ground is the most direct route to ground, if they had no reason for it? Or what could be their reason, and would the reason also apply to the similar application of the breakout-box chassis shield?
Either way, I understand I should run a direct lead from the ground connector, to the chassis shield.. likely a line soldered to the connector, and possibly screwed and soldered to the shield. Will the size of the breakout box chassis, and shielding, have an impact on the projects system performance? Maybe less so coming through the power ground?
As it is right now, I think I'm going with the power route, even if this is counter to logitech's decision on the vga cable shield.. Thanks again diyAudio community for your attention to the matter and contributions.
(4)
http://blog.jseaber.com/wp-content/uploads/2010/04/remoteV100.pdf
(5)
"WA1 & WA2 |Black (big)| Are common or Ground.. Also Audio Ground | CASE |"
post 9
http://www.electro-tech-online.com/threads/logitech-z-2300-controller.100515/]
Logitech Z 2300 Controller | Electronics Forum (Circuits, Projects and Microcontrollers)
The power ground's chassis connection is required for safety. Because this is necessary,
the audio ground often is isolated from the chassis by a small resistor to reduce noise.
In power amps, sometimes a 30A rectifier block is used instead to handle larger fault currents.
Hi. I think this will help you see how to keep the different returns separate and avoid loops. It is by member Bonsai http://hifisonix.com/wordpress/wp-c...re-up-a-Power-Amplifier_Updated-Autosaved.pdf
Hopefully after you have read Bonsai's .pdf you have a better idea.
The mains powered system must have a Protective Earth (PE) to protect users/operators from major mains faults.
This is a safety requirment and is completely separate from Audio. Unfortunately some countries refer to the PE as "ground" and this causes avoidable confusion. Try to separate the Safety from the Audio in your mind.
Now to the audio.
Every inter-module signal connection needs two wires. The Source sends out a current and that current MUST RETURN to the Source. There are no exceptions. Two wires to carry the Flow and Return currents. They can be mains power or loudspeaker , or PSU power, or line level.
Your two wire connection can come in many varieties:
a.)
Coaxial, where the core carries the Flow current and the outer carries the Return current
b.)
Close coupled pair, where the two insulated wires are close to each other either parallel or twisted. Again one of the wires carries the Flow current and it's partner carries the Return current back to the Source.
c.)
Screened Twisted Pair (STP), where one core carries the Flow current and it's partner carries the Return current. The screen around the outside attenuates interference and does not carry any signal current. This is usually connected to the enclosure at both ends. It can be connected at one end only but this reduces the High Frequency attenuation, i.e. not as good at keeping out interference.
Note in the above that a. and c. both have a woven screen.
a carries signal and is exclusively a signal wire, c is exclusively an interference attenuator and does not carry signal. Make sure you know what your screen is doing and allow it to do it's job properly.
The mains powered system must have a Protective Earth (PE) to protect users/operators from major mains faults.
This is a safety requirment and is completely separate from Audio. Unfortunately some countries refer to the PE as "ground" and this causes avoidable confusion. Try to separate the Safety from the Audio in your mind.
Now to the audio.
Every inter-module signal connection needs two wires. The Source sends out a current and that current MUST RETURN to the Source. There are no exceptions. Two wires to carry the Flow and Return currents. They can be mains power or loudspeaker , or PSU power, or line level.
Your two wire connection can come in many varieties:
a.)
Coaxial, where the core carries the Flow current and the outer carries the Return current
b.)
Close coupled pair, where the two insulated wires are close to each other either parallel or twisted. Again one of the wires carries the Flow current and it's partner carries the Return current back to the Source.
c.)
Screened Twisted Pair (STP), where one core carries the Flow current and it's partner carries the Return current. The screen around the outside attenuates interference and does not carry any signal current. This is usually connected to the enclosure at both ends. It can be connected at one end only but this reduces the High Frequency attenuation, i.e. not as good at keeping out interference.
Note in the above that a. and c. both have a woven screen.
a carries signal and is exclusively a signal wire, c is exclusively an interference attenuator and does not carry signal. Make sure you know what your screen is doing and allow it to do it's job properly.
Last edited:
But if he is using a listed wall brick power supply, there is no need to ground his chassis to PE. The power supply can be left floating up the the device. No need to bond power ground to the chassis at the breakout box.
If an AC line powered supply is used inside the box, then yes PE should be attached to the chassis but there are ways around that too. Look at all the consumer audio gear in metal cases that have un-grounded power cords. As long as the power supply conforms to leakage standards, there is no requirement for PE.
The PE connection contributes the most towards hum problems. Why use if it if safety is not an issue.
Last edited:
Here is a diagram, i have made, to describe what I have designed and am thinking of doing for the breakout box.
Is this design, as described in the diagram good posted below good or faulty? My only un-shielded part between signal and power ground, in open air, is the power solder cups in the dsub cable connector.
And also I was thinking of maybe not running un-shielded wired, for the internal breakout dsub cable lines.. because it would save me substantially project costs, relationally. Do you think this(having the wires un-shielded inside) would introduce problems, as described with inductance or stray capacitance, and do you guys think that having the internal wires shielded is necessary to deal with avoiding these electronic relationships?
Thanks for taking the time to respond fellows for helping out with the project.
https://scontent-yyz1-1.xx.fbcdn.ne...=18fd7ffe7de465b14704ce62d95d7b58&oe=59ACD97C
I'm not planning on moving to wall wart yet.. This system has a 150.9 VA center tapped toroidal transformer (150.9VA --> 20.1V X 2, 3.75A), and i think the buying of external power supplies can hopefully be avoided at this point. I might investigate such an avenue sometime, but presently, I'm just interested in designing the breakout box solution. I looked into the pdf article shared, but im just looking for designing hopefully a quick fix, maybe on day i'lll try to read more into things.. but right now i'd just like to get the breakout solution made well and hopefully this design passes your more well versed fellows inspection. If you will lend your expertise to aid my efforts.
Is this design, as described in the diagram good posted below good or faulty? My only un-shielded part between signal and power ground, in open air, is the power solder cups in the dsub cable connector.
And also I was thinking of maybe not running un-shielded wired, for the internal breakout dsub cable lines.. because it would save me substantially project costs, relationally. Do you think this(having the wires un-shielded inside) would introduce problems, as described with inductance or stray capacitance, and do you guys think that having the internal wires shielded is necessary to deal with avoiding these electronic relationships?
Thanks for taking the time to respond fellows for helping out with the project.
An externally hosted image should be here but it was not working when we last tested it.
https://scontent-yyz1-1.xx.fbcdn.ne...=18fd7ffe7de465b14704ce62d95d7b58&oe=59ACD97C
I'm not planning on moving to wall wart yet.. This system has a 150.9 VA center tapped toroidal transformer (150.9VA --> 20.1V X 2, 3.75A), and i think the buying of external power supplies can hopefully be avoided at this point. I might investigate such an avenue sometime, but presently, I'm just interested in designing the breakout box solution. I looked into the pdf article shared, but im just looking for designing hopefully a quick fix, maybe on day i'lll try to read more into things.. but right now i'd just like to get the breakout solution made well and hopefully this design passes your more well versed fellows inspection. If you will lend your expertise to aid my efforts.
Last edited:
Good or faulted?
Hello again. I have made two new rough visual plans, for plan b v*; to describe what im planning on doing, regarding the line level breakout solution and the ground/return relationships.
I just want to know, for now, if you guys think this design, part of the preamplifier system, is good, electronically, or faulty, and if I'm missing something? Please advise. Thank you for your attention.
Imges straighten up to oar(original aspect ratio) when selected.
Hello again. I have made two new rough visual plans, for plan b v*; to describe what im planning on doing, regarding the line level breakout solution and the ground/return relationships.
I just want to know, for now, if you guys think this design, part of the preamplifier system, is good, electronically, or faulty, and if I'm missing something? Please advise. Thank you for your attention.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Imges straighten up to oar(original aspect ratio) when selected.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.