Chip amp power supply- a beginners guide

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 ...

An externally hosted image should be here but it was not working when we last tested it.

... 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 ;)
 
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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 ...

An externally hosted image should be here but it was not working when we last tested it.
... 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.
 
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
 

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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 ...

An externally hosted image should be here but it was not working when we last tested it.

... 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.
 
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.
 
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. ;)
 
Is earth ground (the metal case?), the same as circuit ground?
Not necessarily.

Can they be separate entities?
Yes.

Should they?
No.

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.

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.

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.
 
The Audio Ground is completely different from the Protective Earth (PE)

The PE MUST be permanently connected to the chassis. This is not optional.

Keep those three statements in mind and go back through your literature and separate the wheat from the chaff. It should all sort itself into two categories:
a.) Follow this tip/advice.
b.) Ignore this nonsense.

Have you read my "test" of the Disconnecting Network?
 
...When power is turned on, measure the voltage between the non-joined ends of the secondary windings and compare to the voltage between either non-joined end and the joined portion in the middle. Voltage between the non-joined ends should be double the voltage between either end and the joined center tap.

If you join the wrong end of the secondary together the voltage of one will cancel out the other...

Hey ! - Thanks or this reminder. I was testing a small r-core tranny that had 2 sec windings with no diagram, or color-coding to distinguish the sides of each winding. I needed to tie them together in serial fashion to get a CT arrangement. At first I was getting my two half voltages of 19vac, but across each non-joined end I was getting zero. I changed the leads and voila. I got my double voltage of 38vac. I had forgotten that out of phase will cancel the voltage. :eek: Maybe it doesn't matter if all you will be using is the CT configuration. It's to bad there is not some industry standard diagrams and markings that clearly denote to the user how the tranny is wound - and meaningful color-coding. I can imagine many trannies with 2 secondary windings being used in CT situations. It's easy enough to test for, but still the newbie may be confused.
 
Hi there,

What's the difference in sound between Carlos's regulated and unregulated versions regarding the lm3886 ?

I read somewhere, that regulated version, somehow, produce lifeless sound . I'm not really sure of that.

Anyway , I want to build one of the them as my first GC psu , but really hesitated which of them I should build. Any advice ?
 
MrAdel1984

I would suggest to start with the simplest unregulated and listen to that for a bit as you build the more complex version. You can decide which suits your ears best once you have lived with them for a while.

If it is a first build keep it simple for a better chance of first time success and use a lightbulb tester to power it up.

John