Grounding question

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#101
I have seen people use a 6-connection star tag, bolted to the chassis, for their 'star'.
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i have seen this many japanese amps akai, pioneer, sansu's in the 80's ....wires were either wrapped on the pins and then sone soldered....

currents can only flow thru the chassis if there is a ground loop, that is why Leach used 10 ohms isolation resistors....when the chassis is used to run psu currents, i never practice that in any of my build...

this is the sequence i follow....one ring lug on top of the other...

1. power transformer center tap
2. the two speaker returns leads
3. the main filter cap leads
4. the pc board grounding

no washers in between ring lugs, washers are used only at the top with flat and spring washer and then nut and tightened accordingly....

this is how i implemented my grounding ever since and it worked for me....
 
#102
The charging circuit around the transformer rectifier smoothing caps MUST be together to keep the pulses separate from all other circuits.
This "togetherness" applies when the PSU wiring is separate from the Main Audio Ground or adjacent to it with a very short single wire/trace connection or a set of ring tags on a common bolt.

There is nothing wrong with the ring tags on a common bolt, provided the "order" of assembly keeps the currents within their own circuits. I gave this as a solution many years ago. D.Self also shows it.
DF in post 100 describes it.
Putting several tags on one bolt means that again you have a bus, connected to the chassis at one end.
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You should swap 2 & 3
1. power transformer center tap
2. the two speaker returns leads
3. the main filter cap leads
4. the pc board grounding
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The separate circuits are
power transformer Centre tap to smoothing caps. This becomes tags 1 & 2
speaker returns to PCB board. This becomes tags 3 & 4
PCB board to Signal Returns This becomes tags 4 & 5
giving

1. Transformer centre tap
2. Smoothing cap junction
3 Speaker return
4 PCB power ground
5 Signal ground.
If Chassis is to be connected it becomes tag0 adjacent to tag1.
 
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#109
number7 said:
Because I haven't got sufficiently sophisticated test equipment - just because something doesn't blow up, does not necessarily mean it's the best solution!
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kindly read my post again, "If you take a gander at most amps posted here, that's how things are connected."
that comment about not blowing up anything was meant to give you confidence.. this is diy, ain't it?
 
#111
Number7
Don't change the schematic just fix the power supply central grounding scheme.
E.g disconnect the 4 big caps high current flow from copper sheet thingy.
I reckon youll resist this modification since its central to your build mechanics, and look to quick fixes that will NOT completely stop the hum issue at its NUMBER1 source.

Rectifier wired directly to 4 caps then add a central wire to a common bus bar (star point ) float this bus bar and make only one connection to chassis from the bus bar (besides SE green at the IEC input ).
You have done basic trouble shooting for external hum causes right?
 
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#112
number7 said:
Not as far to go as you think 😉 Just not happy with the performance yet.

Class A Monoblock Power Amplifier - Product Design Showcase
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Very nice build quality, impressive.

That said, your solid copper ground will radiate cap charging currents as a magnetic field around the copper itself, running parallel to the copper, and at a right angle to the path. That magnetic field can be coupled to wires that travel along it. You pass the input cable along it as well as the speaker outputs.

It would be better if you could reduce that coupling effect.

In EMC practice, three things are needed to create the hum. A source, which your copper plate is, a victim, which is your input as well as the active circuitry, and a coupling mechanism, which is the magnetic field.

Your solid copper plane is a very very good E field shielding. But you are not coupling E field hum, but instead, magnetic field. You need to reduce the creation of the magnetic field and get some distance between it and the sensitive parts.

John
 
#114
jneutron said:
Very nice build quality, impressive.

That said, your solid copper ground will radiate cap charging currents as a magnetic field around the copper itself, running parallel to the copper, and at a right angle to the path. That magnetic field can be coupled to wires that travel along it. You pass the input cable along it as well as the speaker outputs.

John
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Yes, I am already in the process of re-designing / making a revised Cap layout. Thanks
 
#115
infinia said:
Number7

I reckon youll resist this modification since its central to your build mechanics, and look to quick fixes that will NOT completely stop the hum issue at its NUMBER1 source.
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Don't ever get a job that involves interpreting human behaviour - you will suck 🙂

If you look at the build, I am hardly someone who relies on 'quick' fixes. The amps are stripped and ready for some new artistic copper sculpting!
 
#116
The amps are stripped and ready for some new artistic copper sculpting!
*
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sigh..see, I knew it's all about the copper. You don't need new copper. Just disconnect from it and add a little rewiring. .. to test things one thing at a time. Spreading it out for testing before packaging was also a good suggestion.
don't get a job on a jury... you'd suck at awarding prizes.😉
"Who does number2 work for?" LOL

'human nature' is well documented RE taking the easy path.
 
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#117
Its interesting to note that if this amplifier was a Class AB (w/o bleeders), instead of Class A, it's very likely this hum issue would have been never been discovered by the OP. nonetheless its still an issue as viewed on a Spectrum analyzer. A loud single tone might uncover it, but who listens to pure sinewaves.
 
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