Apologies if this has already been covered, being a beginner the more I read on grounding the more confused I get!
The pic attached shows the grounding arrangement suggested by the supplier of the LM3886 boards I just received. I've read around here that signal and power grounds should be kept separate which doesn't appear to be the case here.
Any opinions on what should be the ideal set-up would be greatly appreciated.
Thanks,
Andy
The pic attached shows the grounding arrangement suggested by the supplier of the LM3886 boards I just received. I've read around here that signal and power grounds should be kept separate which doesn't appear to be the case here.
Any opinions on what should be the ideal set-up would be greatly appreciated.
Thanks,
Andy
Attachments
You know I could be wrong but I would only ground the chassis from the side of the board near the transformer.
1) Use a star ground at the output of PS board, including one chassis connection ie 3 wires total. (speaker out returns may be best connected here as well)
2) Delete chassis connection at input of the PS board and twist the 3 XFMR secondary wires together.
3) Use shielded or twisted wires at RCA input and float chassis ground at the RCA connectors.
4) Mains safety ground wired directly to chassis. Thus there should only be 2 wires tied to chassis including this.
2) Delete chassis connection at input of the PS board and twist the 3 XFMR secondary wires together.
3) Use shielded or twisted wires at RCA input and float chassis ground at the RCA connectors.
4) Mains safety ground wired directly to chassis. Thus there should only be 2 wires tied to chassis including this.
Thanks for this, can you clarify what you mean by floating chassis ground at the RCAs?
Like I say, I'm still learning and don't want it all to go bang!
Almost, the RCAs run to amps PCB input. Before you hook things up , redraw your diagram with what I said.
nice
The speaker return from the panel shuns the amp PCB and routes directly to the star ground.
so in addition to the grounds, The speaker out has only one wire from the amp PCB and another from star ground on the PS PCB. The input has 2 twisted wires from the amp to the floating RCA.
The speaker return from the panel shuns the amp PCB and routes directly to the star ground.
so in addition to the grounds, The speaker out has only one wire from the amp PCB and another from star ground on the PS PCB. The input has 2 twisted wires from the amp to the floating RCA.
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Star ground is no good for this case.when connected a source,there are big loop between the source left output <-> unbalanced RCA cable <-> the amp left RCA input <-> left amp pcb <-> star ground point <-> right amp pcb <-> the amp right RCA input <-> unbalanced RCA cable <-> the source right output <-> inner source circuit <-> the source left output.this loop is signal level.
So if you set up two or more amp pcb into a single chassis.you have to 'STACK' the ground track on each pcb 'TOGETHER' to pass away the loop between the source & amp.
I think a strong ground bar would be better.
Can you read this thread?
http://www.diyaudio.com/forums/chip...g-star-grounding-post1403793.html#post1403793
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Hi digi01 good diagrams
All of your diagrams show that the loop still exists, the so called stacking by using bus bars and/or heavy gauge wires only tries to steer the PS ground currents away from the interconnects. That's why you also recommend cutting the interconnect shields at one end!
An even worse situation exists because of other external noise currents from sources that travels across the interconnects to the amps chassis/safety earth 3 prong plug. The stacking does nothing to stop this other kind of interference. Another approach I think is best is using small 10 ohm resistors in series with the signal grounds at the amps RCA input, this routes the bad currents better than heavy bus bars IMO.
I think there are some problems mixing DIY equipment that is safety connected to earth and connecting commercial gear ( sources) that is only AC connected via 2 prong plugs.
All of your diagrams show that the loop still exists, the so called stacking by using bus bars and/or heavy gauge wires only tries to steer the PS ground currents away from the interconnects. That's why you also recommend cutting the interconnect shields at one end!
An even worse situation exists because of other external noise currents from sources that travels across the interconnects to the amps chassis/safety earth 3 prong plug. The stacking does nothing to stop this other kind of interference. Another approach I think is best is using small 10 ohm resistors in series with the signal grounds at the amps RCA input, this routes the bad currents better than heavy bus bars IMO.
I think there are some problems mixing DIY equipment that is safety connected to earth and connecting commercial gear ( sources) that is only AC connected via 2 prong plugs.
Where you've broken the connection to the chassis ground insert a CL-60 thermal inrush limiter -- and you'll have a Zen-Like ground-breaker. (If that's allowable in the UK.) You can also put a pair of CL-60's on the primary side of the transformer.
I think that would be a very good idea in-series with the chassis connection at the output of the filter caps but not at the input due to high ripple currents.
EDIT>Me I would build it to Class II standards, LOL.
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Quick update.
I compared the star grounding shown on post 8 with the "stacked" method with a thick ground bar. Stacked gave me some very slight hum, star was silent.
I think I'll leave it as a star for now and just enjoy it until the urge to tinker comes along again!
Thanks once again for your input folks.
Andy
I compared the star grounding shown on post 8 with the "stacked" method with a thick ground bar. Stacked gave me some very slight hum, star was silent.
I think I'll leave it as a star for now and just enjoy it until the urge to tinker comes along again!
Thanks once again for your input folks.
Andy
Hi Andy
Glad things are working out for you.
What transformer did you get?
Pictures are always welcomed
Glad things are working out for you.
What transformer did you get?
Pictures are always welcomed
Hi,
lot's of air is the best interference suppressor (J.C. said something along those lines).
Nice twisting on the low level lines.
Twisting is just as important on the high level lines (pairs or triplets).
lot's of air is the best interference suppressor (J.C. said something along those lines).
Nice twisting on the low level lines.
Twisting is just as important on the high level lines (pairs or triplets).
Looks really good, can't tell its not by an expert amp builder!
Has plenty of room for future growth, maybe to add another pair of chipamp boards. Bi-amp and active filters?
Has plenty of room for future growth, maybe to add another pair of chipamp boards. Bi-amp and active filters?
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