First Lm3886

[Stuey]

Originally posted by PJPro
Errr. The above bits have just arrived. The resistors are absolutely massive....the biggest I've ever seen!

It's not the size that matters, it's what you do with it that counts....

Quote from 'The Life and Times of Stuey's Wife'.

[Ted205]

Building a lm3886 with no / little hum is very possible and a good way to learn about star grounding

http://www.passdiy.com/pdf/articles/ground-loops.pdf

^informative article from the passlabs site

starting with the disconnecting network you are fixing a problem that doesn't exist (at least not yet)

best to make the amp, then when/if hunting ground loops use the disconnecting network as a tool to help solve the issue. Just my opinion


On a seperate note, is the classI/II regs international or just a european thing ?

[infinia]

Andrew you should NOT attack the man (me) just their idea's.
There are another ways to solve ground loops (if you have it) rather than the mains end. The answer is posted above it's easy. As also stated, there are legal questions with lifting a safety ground period, if you do something else other than directly bonding earth to chassis then you are on your own.

[AndrewT]

Hi Inf,
it's not an attack.
I genuinely believe that you and the others, including me, seem to see the Safety Earth connection differently.
I can only explain this difference in stance by saying you do not understand what we are posting about. Would "appear not to understand" sound any better?

[AndrewT]

Originally posted by infinia
there are legal questions with lifting a safety ground period, if you do something else other than directly bonding earth to chassis then you are on your own.

That's is where you do not understand our posts.
We keep repeating that the third wire (PE) of the mains incoming cable must be permanently connected to chassis. That stance of ours has never changed.
Why do you suggest that we are advising otherwise?

I and I think I speak for the others have never said that a Ground Lift Switch should "break" the Safety Earth connection to the other exposed parts nor can it be allowed to "break" the chassis to mains PE connection.

The Ground Lift Switch that is being described is in parallel to the Disconnecting Network. Opening or closing this switch does not interfere with the Audio Ground to Safety Earth capability to pass fault current.

There seems to be a fundamental misunderstanding in what we are posting and how you interpret what you read.
How else can I put that?

[infinia]

What part of directly don't YOU understand. Prove that wonky network is an approved PE scheme by a safety agency. A ground loop can be minimized in the most susceptable part of a ground loop ie the signal ground shield.
I have guided several of my designs thru UL certification and even one through UL listing which is the most rigorous.
My current speciality is RF systems susceptibility and I have been part of tiger teams to solve grounding and noise issues in complex analog/digital systems.
I suggest you review the mechanisms of audio ground loops and their solutions.

[pacificblue]

Bryston amplifiers have that network in all schematics I have seen so far from them. Bryston is a Canadian company, so it is very likely that they have UL or ULC certification. If you have achieved certification with one of your products, you will get or already have a list with all certified products from UL, where you can look up, if my assumption is correct.

[PJPro]

I'm starting to question my own understanding of the schematic.

If we ignore the disconnecting network entirely, the Safety Earth is clearly shown with a direct and dedicated connection to the earth from the power inlet module. This provides a route to earth for any fault which happens to result in the chassis becoming live.

Is this not directly bonding earth to the chassis? Am I misunderstanding this part of the schematic?

[infinia]

Is that product listed by the UL, I don't think it is. That is your claim not mine. The burdon proof is still in your court if you still maintain that is an accepted and approved safety standard. BTW it isn't. It's possible that you can get an exception, but it is a lot of unecessary work and controls will be put upon you the manufacturer to be even considered. But why go that route in the first place. There are more effective solutions to be had.

[PJPro]

I'm less interested in the disconnecting network and more interested in establishing whether I have the direct bonding between the chassis and earth.

Can someone confirm my understanding of the schematic?

My practical implementation will be to run a wire from the earth connector on the power inlet module and and bolt it directly to the chassis. This bolt will service no other connection other than to accomodate this wire.

Should I assume that this is the correct approach?