I understand that idealy we want all of our grounds wired to one spot or star ground...
In my build every terminal strip has a tab thats supposed to be at ground, and is always the same lug connected to the mounting tab for obvious reasons...
Aree we supposed to lift that terminal strips mounting tab with associated nuts and bolts off thr metal chassis or is running a hookup wire from that ground tan to the main star ground enough?
In my build every terminal strip has a tab thats supposed to be at ground, and is always the same lug connected to the mounting tab for obvious reasons...
Aree we supposed to lift that terminal strips mounting tab with associated nuts and bolts off thr metal chassis or is running a hookup wire from that ground tan to the main star ground enough?
Don't use the grounded terminals if you want a star ground or bus ground. Actually you don't need to do either if you don't have noise currents flowing in the chassis. Keep Power supply return current out of the chassis (especially the filter capacitors!); ground the output transformer secondary near the point of feedback (if used) and run the speaker output from there. Vintage equipment was hum-free (even phono preamps!) without star grounding until modern DIYers got hold of it.
I wish "star grounding" would be debunked once and for all. Most attempts at this, seriously degrade
the functioning of the circuit. The concept is usually physically impossible in practice anyway, even though
some still try to jam a whole bunch of lugs under one screw, which is prohibited in industry for reliability reasons.
the functioning of the circuit. The concept is usually physically impossible in practice anyway, even though
some still try to jam a whole bunch of lugs under one screw, which is prohibited in industry for reliability reasons.
Don't use all those "grounded" terminals at all. That will cause ground loops and hum.
Use strips like this instead. Then you can bolt them to the chassis tightly and securely.
Attachments
I really believe that all of this confusion is because folk believe the "ground" symbols on schematics. Because they believe there to be these dragons, they don't worry about current flows - after all, "ground" is perfect, and magically sinks and sources current. That's the way I was raised, and it took many moons to overcome that bad thinking. Many.
All good fortune,
Chris
All good fortune,
Chris
If we said "black hole" instead of ground, maybe some would catch on, that the term is at best metaphorical.
I try to use the original term "common" instead, which implies more of a logical relation, than a physical one.
I try to use the original term "common" instead, which implies more of a logical relation, than a physical one.
running a wire from a ground eyelet to ground is ok. It keeps Larry's ground in check.
I use an non insulated turret when I want to bond to Larry's ground
And there's also all that dirt in the backyard. Which Hams call "ground".
I'm thinking that somehow schematics make us think about things in voltages, because that's what we can point at, measure and print on schematics. Currents run "inside" on schematics, so don't seem as real, or at least as immediate. Or is it a simpler matter of just changing perspectives that other people can do much easier than me? Both are views of the same world, but for this issue, current "flow" is the interesting perspective. Maybe just a more complete model (schematic) really is the best solution. You're right, of course, but know that nobody's going to thank you for this. Arf!
Much thanks, as always,
Chris
I'm thinking that somehow schematics make us think about things in voltages, because that's what we can point at, measure and print on schematics. Currents run "inside" on schematics, so don't seem as real, or at least as immediate. Or is it a simpler matter of just changing perspectives that other people can do much easier than me? Both are views of the same world, but for this issue, current "flow" is the interesting perspective. Maybe just a more complete model (schematic) really is the best solution. You're right, of course, but know that nobody's going to thank you for this. Arf!
Much thanks, as always,
Chris
This is my grounding scheme I use to bond. DC GND can be a star ground or not..
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That is because it supposed to be soldered together to an eyelet terminal or turret. Sometimes, I'll even use the negative lead eyelet of the power supply cap sometimes.
People using crimp on lugs for DC grounds are doing it wrong. The only lug I will use is my AC cord FG (green) to chassis and I even solder the wire after I crimp it.
I have had people argue this, but I've been just running a wire from that mounting lug to the "star ground" and never had any issues. Theoretically there should be ground loops, but in practice, I've never had a problem. YMMV
That said I only scrape the paint and am careful to get a very solid ground at the star ground point. I also use 18ga solid copper wire to bring the remote grounds into the main ground. Sometimes theoretical problems just don't exist in practice. Another example is using a steel chassis. I've build dozens of amps with steel and never had any inductance noise issues.
One other issue that hasn't yet appeared in this thread is the PE chassis "ground". UL code calls for the mains third wire/ safety ground/ PE to be bolted to chassis with its own dedicated screw, lockwasher, nut, etc. Seems excessive when in the throws of creativity building an amplifier, but they have a reason, and it's easy enough to do it code with just a little prep. Call me a Safety Sally, I can take it.
All good fortune,
Chris
All good fortune,
Chris
I bolt mine to the transformer mount and they have no issues passing them. It just has to be bonded.
BTW, I did call someone on the grounded speaker secondary and that doesn't have to be grounded unless you are providing a speaker out connection. Because they classify it as a portable device otherwise with a built in speaker.
But to me, I don't care if go and use a certified double insulated transformer, and a non polarized plug. They would pass that too. I would put a polarized plug on it just so that they plug it in the same way, but even that wouldn't make a difference.
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Yeah, anything enclosed should be fine. Forum rules don't allow discussion of hot-chassis historical stuff, except as a learning tool, but it's important for all builders to understand the basic mechanics of safety issues. Sometimes some things might seem too hypothetical or whatever, but as Barry Goldwater almost said "Extremism in the defense of safety is no vice."
I'm sometimes in the position of teaching firearms handling to newcomers. That responsibility changed me, and made me appreciate the overlapping layers of Jeff Cooper's four rules of safe firearms handling. They're designed so that a single rules failure most probably won't hurt anyone. Two failures might. I've become a Safety Sally, and still wear a mask into the grocery store, so sue me.
As DIYers, we have a personal moral responsibility to not hurt anyone, and I'm the local dipweed always reminding folk how dangerous things can be. Not a well paid gig, but regular work.
All good fortune,
Chris
I'm sometimes in the position of teaching firearms handling to newcomers. That responsibility changed me, and made me appreciate the overlapping layers of Jeff Cooper's four rules of safe firearms handling. They're designed so that a single rules failure most probably won't hurt anyone. Two failures might. I've become a Safety Sally, and still wear a mask into the grocery store, so sue me.
As DIYers, we have a personal moral responsibility to not hurt anyone, and I'm the local dipweed always reminding folk how dangerous things can be. Not a well paid gig, but regular work.
All good fortune,
Chris
Yes, one ground point located at the most sensitive input of the chassis, but NO star ground for me - only electronic logical order ground wiring.
But it's me, OK ? 😉
T
I 100% never share the safety ground with anything. It's easy enough to just drill another hole right next to the IEC connector and run a short, separate dedicated ground there.
Yes, I always ground the output transformer negative leads to the chassis. If for some reason the OT has an internal short, without the output grounded, you could have hundreds of VDC on the speaker terminal. With it grounded, the fuse would blow.
I connect all grounds to chassis including directly connecting electrical ground (green). Not only does this provide effectively no hum or buzz, but it's actually posible to use single wire signal with earth as return. No more super loud buzz while disconnecting RCA cables.