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Old 5th March 2012, 05:09 PM   #681
AndrewT is online now AndrewT  Scotland
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All exposed conductive parts must be connected to Safety Earth.
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Old 5th March 2012, 05:34 PM   #682
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Quote:
Originally Posted by redjr View Post
I haven't read through the document fully yet, and I won't be constructing my own PSU, but one quick question before I start wiring up my chip-amp. This is very basic and easy... Is it common practice to tie the PSU ground to earth ground at some point, or does it float internally? What about all the connectors that fit to a metal enclosure?
There is one point where all ground and earth connections can be made. This may be based on your particular design. If (as in your case) the power supply will be separate from the amp case(s), then the "local ground" and earth connection (usually but not always = chassis ground) may be connected at only one point inside each shielded case. (There is a whole field of research, study, advise and common practical applications where specific guidelines are laid out for this "common ground point" as it is almost always important ... This in order to prevent ground loops, within each case and when treating the whole set of PS + amp(s) and pre-amps as a system. See Wikipedia for the gory details: http://en.wikipedia.org/wiki/Ground_loop_(electricity) )

Note there are many lengthy discussions about the ground loop question here at DIYAudio ...

----- Of Interest -----

This type of device solves a number of difficult DIY power supply construction questions ... eliminating multiple chassis holes, several redundant filtering elements and a fuse and making for a neat and slick solution ...

Click the image to open in full size.
... A laboratory grade device that includes the switch, line cord plug, filtering elements and the fuse, all in one.

Note that the chassis lug for earth ground can (and usually should) be connected to the common ground point within the power supply case. Click for details

Last edited by FastEddy; 5th March 2012 at 05:47 PM.
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Old 5th March 2012, 06:00 PM   #683
redjr is offline redjr  United States
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Quote:
Originally Posted by FastEddy View Post
There is one point where all ground and earth connections can be made. This may be based on your particular design. If (as in your case) the power supply will be separate from the amp case(s), then the "local ground" and earth connection (usually but not always = chassis ground) may be connected at only one point inside each shielded case. (There is a whole field of research, study, advise and common practical applications where specific guidelines are laid out for this "common ground point" as it is almost always important ... This in order to prevent ground loops, in each case and when treating the whole set of PS + amp(s) and pre-amps as a system. See Wikipedia for the gory details: http://en.wikipedia.org/wiki/Ground_loop_(electricity) )

----- Of Interest -----

This type of device solves a number of difficult DIY power supply construction questions ... eliminating multiple chassis holes, several redundant filtering elements and a fuse and making for a neat and slick solution ...

Click the image to open in full size. ... click for details
Hey Fast - That's what I thought, but was unsure. Actually, in my case (no pun intended) I just won't be constructing my PSU per se. I'm using pre-built modules, and it will be in the same enclosure as my amp modules, so everything can be tied off properly to earth ground.

I came of age in my electronics training when there was no IEC spec that we have today that adds the third earth ground to the mix. And since it's been decades since that formal training, I need to refresh much of the practical use and application. Luckily the internet and sites/threads like this make it very easy and the body of electrical knowledge is vast and free!

I've read about using the star grounding strategy, but if the case is metal why not just use the case as the ground plane. If you still shield the audio input cables but do not connect up one end of the shield, that should minimize ground loop when using the case as the g-plane. Is that a correct statement.

I do plan on using one of those IEC connectors with switch and possibly even a fuse, all built-in. That seems like a smart way to go to minimize wiring.
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Old 6th March 2012, 01:14 PM   #684
gadut is offline gadut  Indonesia
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I have found in local store for Black Gate F 680uF 65V with fair price - around $4.5/pcs, i'm considering to use it as C supply for LM3886 to replace Nichicon KG 1000uF 50V. Is it sufficient to use 680uf instead of 1000uf?

I'm still choosing the best one for the snubber psu :
- Nichicon KG 10.000 uf x 8 - $9/pcs - total $72
- Nichicon KG 4700 uf x 20 - $1.7/pcs - total $34
but the 4700uf version is gold casing, the seller told me that it's the previous version of KG instead of black casing..the 'normal' one that I find in the web is that the casing should be black, like my 2200uf. any clue about gold casing of this nichicon KG? is it possible a counterfeit version?

attached image show the caps that i get
Attached Images
File Type: jpg KG1.jpg (19.2 KB, 412 views)
File Type: jpg KG2.jpg (19.1 KB, 381 views)
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Old 6th March 2012, 02:06 PM   #685
SoIL4x4 is offline SoIL4x4  United States
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Quote:
Originally Posted by FastEddy View Post
There is one point where all ground and earth connections can be made. This may be based on your particular design. If (as in your case) the power supply will be separate from the amp case(s), then the "local ground" and earth connection (usually but not always = chassis ground) may be connected at only one point inside each shielded case. (There is a whole field of research, study, advise and common practical applications where specific guidelines are laid out for this "common ground point" as it is almost always important ... This in order to prevent ground loops, within each case and when treating the whole set of PS + amp(s) and pre-amps as a system. See Wikipedia for the gory details: http://en.wikipedia.org/wiki/Ground_loop_(electricity) )

Note there are many lengthy discussions about the ground loop question here at DIYAudio ...

----- Of Interest -----


This type of device solves a number of difficult DIY power supply construction questions ... eliminating multiple chassis holes, several redundant filtering elements and a fuse and making for a neat and slick solution ...

Click the image to open in full size.
... A laboratory grade device that includes the switch, line cord plug, filtering elements and the fuse, all in one.

Note that the chassis lug for earth ground can (and usually should) be connected to the common ground point within the power supply case. Click for details
I could be wrong but I seem to remember reading somewhere that the iec units that have built in filtering redirect any unwanted ac noise into the ground path, making them less than desirable for audio applications. But again I have never used one so I cannot say for sure.
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Old 6th March 2012, 02:10 PM   #686
AndrewT is online now AndrewT  Scotland
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The filters do indeed direct the HF to the Earth Terminal.
That Earth terminal is connected to PE. That is not an option The IEC Earth must be also be connected to chassis, permanently. Again no option.
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Old 6th March 2012, 02:38 PM   #687
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Quote:
Originally Posted by gadut View Post
I have found in local store for Black Gate F 680uF 65V with fair price - around $4.5/pcs, i'm considering to use it as C supply for LM3886 to replace Nichicon KG 1000uF 50V. Is it sufficient to use 680uf instead of 1000uf?

I'm still choosing the best one for the snubber psu :
- Nichicon KG 10.000 uf x 8 - $9/pcs - total $72
- Nichicon KG 4700 uf x 20 - $1.7/pcs - total $34
but the 4700uf version is gold casing, the seller told me that it's the previous version of KG instead of black casing..the 'normal' one that I find in the web is that the casing should be black, like my 2200uf. any clue about gold casing of this nichicon KG? is it possible a counterfeit version?

attached image show the caps that i get
680uF is a bit on the low side. You should be looking at about 10000uF per rail. This can of course be made up by adding smaller capitors together in parallel.
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Old 6th March 2012, 02:57 PM   #688
gadut is offline gadut  Indonesia
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Quote:
Originally Posted by KatieandDad View Post
680uF is a bit on the low side. You should be looking at about 10000uF per rail. This can of course be made up by adding smaller capitors together in parallel.
It's not for power supply unit, but Cs in schematic shown. My psu will be 25.000uF per rail. If i refer to shine7 PA100, he used Cs as BG F 1000uf, while I only have 680uf
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Old 14th March 2012, 06:04 PM   #689
redjr is offline redjr  United States
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Originally Posted by AndrewT View Post
All exposed conductive parts must be connected to Safety Earth.
I'm reading a lot of information with respect to grounding and in some instances it seems to be contradictory. I just want to make sure I'm clear on the best practice to observe with my construction techniques - whether I'm building an amp, separate DAC unit, or what have you.

Is earth ground (the metal case?), the same as circuit ground? Can they be separate entities? Should they? IOW, your statement above leads me to believe that the outside shield of an RCA connector, fastened to a metal case - since it is exposed - is connected to earth ground. Yes? Making earth ground and circuit ground one in the same. Is that a true statement? I've been reading some helpful info from Rod Elliott and he suggest and I quote,

"The internal electronics of an amplifier should also be earthed, but now we have the problem of the hum loop again. There are two possibilities here ...

Don't earth the internal electronics, or use a simple 'loop breaker' circuit to allow the case to act as a shield for radio frequency interference, but no solid connection is made (this is a common approach). This provides protection should there be a failure from the incoming mains to chassis, but provides none at all if the transformer were to develop a fault between primary and secondary windings. Such faults are uncommon, but they can (and do) occur.

Use a high current loop breaker circuit, ensuring that even major fault currents will be bypassed to the safety earth conductor. Such a circuit was described as a part of the 100W Guitar Amp project, but is shown again below. Be warned that this circuit (while safe) may not be legal where you live."


He suggests in his first paragraph to not earth internal components, or use a simple "loop breaker". Since you suggest that all exposed connectors (RCA jacks) be earth too - which has been my practice in the past - I'm unclear as to what is common, best practice today when building a simple DIY audio project. Is the 'loop breaker' circuit the best practice and is it used only to eliminate hum, or other safety concerns?

My apologizes for perhaps dredging up old information that no doubt has been beat to death on more than one occasion.
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Old 14th March 2012, 06:23 PM   #690
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Quote:
Originally Posted by redjr View Post
Is earth ground (the metal case?), the same as circuit ground?
Not necessarily.

Quote:
Originally Posted by redjr View Post
Can they be separate entities?
Yes.

Quote:
Originally Posted by redjr View Post
Should they?
No.

Quote:
Originally Posted by redjr View Post
IOW, your statement above leads me to believe that the outside shield of an RCA connector, fastened to a metal case - since it is exposed - is connected to earth ground. Yes?
Depends on the designer's assessment.

Quote:
Originally Posted by redjr View Post
Making earth ground and circuit ground one in the same. Is that a true statement?
Ideally yes, but there are situations where that is not possible.

Quote:
Originally Posted by redjr View Post
He suggests in his first paragraph to not earth internal components, or use a simple "loop breaker". Since you suggest that all exposed connectors (RCA jacks) be earth too - which has been my practice in the past - I'm unclear as to what is common, best practice today when building a simple DIY audio project. Is the 'loop breaker' circuit the best practice and is it used only to eliminate hum, or other safety concerns?
It is not best practice. It is a possibility to deal with ground loops that you cannot get rid of by any other means other than using a ground lift switch. A ground lift switch is often found on professional equipment, but there is the danger of not having it in the right position, when a fault ocurrs. But as Elliott states, his circuit may be illegal where you live. The ground lift switch is not, but puts the responsibility into the user's hand.
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