Star Ground Nodes--Mechanical Issues

[David Root]

I have progressed to using small fiber shoulder washers on a 1/2" 6-32 SS machine bolt, either side of the chassis, tightened to chassis with a SS nut. I used to use nylon, which is a better insulator, but it is too slippery and you can't get it to stay tight. I could glue them in with cyanoacrylate but that somehow doesn't seem the pro way to do it.

I have recently used Mouser part # 534-4698, but the main flange OD is only 0.25" and they sometimes split under tightening up, possibly compromising the insulation from the chassis.

I am thinking of trying Mouser part # 534-3233, which has a flange dia. of 0.375" and should resist splitting a bit better.

Any advice? Is there a better way than the shoulder washers? Is there a better shoulder washer material that won't split or creep?

[skyboltone]

I'm wondering why you need to isolate David? Here is the way I do it.

It is not original, I saw it first with Kendrick amps.

[IMG:597:480]http://i12.tinypic.com/5ytxgyh.jpg[/img]

Those are all single chassis ground tabs, on a 6/32 screw, anchored next to the power transformer with every ground in the chassis going back to that point. 23 of them I think?

[David Root]

I use multiple nodes, usually one per filter cap. They are insulated from the chassis and wired thru each other, effectively forming a buss that grounds everything at a single point at the quiet end of the chassis.

So, if I have 6 nodes, only no. 1 is connected to the chassis. Different from yours but just as effective and probably uses less wire.

[drz400]

I like a big fat busswire
Attached to chassis at only one spot
Local nodes (stars) go to the main buss
Supported by 2 terminal terminals Ground terminal not used.

Never let me down, when I used stars I actually experienced more hum when using 1 star and worked much better with 3, best for me has been the buss.

[mhuss]

I like a big fat busswire
Attached to chassis at only one spot

+1

--mark

[jelle]

+1 on the buss!

Jelle

[ampdan]

Another + for the buss!

[David Root]

I'm having trouble visualizing this from your description, drz400. It sounds like we are doing essentially the same thing but you use thicker wire and support it at both ends only, these "terminal terminal" supports presumably also insulated from the chassis.

Can you upload a pic?

[drz400]

I'm having trouble visualizing this from your description, drz400. It sounds like we are doing essentially the same thing but you use thicker wire and support it at both ends only, these "terminal terminal" supports presumably also insulated from the chassis.

Can you upload a pic?

Imagine a Buss wire that flows across the front of the amp from Input jack to other side.

Basically I found what works best and is covered in the Kevin OConnor book. This is like a monorail that is only terminated to chassis at one point. Each baby star is attached to the rail.

I have done your method but created 3 loops on the chassis which worked nice. I would call that a buss though.

Look at the front edge near the pots on the board
[img:970:459]http://www.proguitar.de/ProGuitarPreisl ... 0Innen.jpg[/img]

[skyboltone]

I don't think I'll ever do it the way I did in the first post. As David points out, way too much wire and work. I can remember seeing a lot of old Collins radio gear with a ground buss circulating around the chassis. They never seemed to care about a single ground point but then again that's all RF stuff not AF. Should be easy enough to use two tab solder strips to keep the thing from making more than one ground attachment.

[David Root]

Ok, now it's clear, drz400. You're putting the buss ON the board. I'm doing exactly the same thing but OFF the board, because I use old style two row turretboards.

I'll have to think about that, maybe I could use the board somehow. It would be simpler to support the buss on the board.

That's a nice layout too, BTW. You use a custom made board.