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Re: Star grounding in Al chassis


 
7/26/2000 12:24 PM
Peter S
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Re: Star grounding in Al chassis
I built the entire amp point to point. The grounds are isolated from the chassis using terminal strips. You could approach this many ways. Anything that keeps the grounds off the chassis so you can run a wire to the star ground point will work.  
 
Peter S
 
7/25/2000 9:19 PM
R.G. Re: How do you attach grounds point to aluminium?
quote:
"just because it's the "industry standard" doesn't make it the best way, it just makes it the easiest and cheapest way."
 
Oh, absolutely - it isn't necessarily best, it's just what gets done most often because  
(a) it works well enough for most purposes  
(b) it's cheap and easy  
(c) it lasts OK if not forever.  
 
That's why I said "industry standard" instead of best. You're correct.
 
7/26/2000 4:40 AM
Bruce
email

My amps are built with virtually no regard to the chassis as part of the "amp's circuitry ground" but I do connect the green ground wire (from the mains) to the chassis ground.  
I don't have very many problems with hum or noise.  
 
Now, as far as what to do with that one last circuit board ground that you want to connect to the chassis, what about the odd goop/grease electricians have used on Al wiring to keep O2 out of the picture?  
I still see it sold at many home improvement stores and the like. Any reason it wouldn't work here?  
By the way, I've looked under old star washers (the ones squishing ground wires down to the aluminum chassis) that I put in 4 or 5 years ago and the chassis still look totaly new under them.  
Something must be working OK with that plan.  
 
Bruce
 
7/26/2000 1:31 PM
Ken Gilbert
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strictly speaking, all of the old literature i've read has said to connect chassis ground and signal ground right AT the input jack. i usually do that, eliminating the fiber insulating shoulder washer from the 1/4" input. it seems to work pretty damned well.  
 
ken
 
7/26/2000 5:00 PM
Peter S
email

Ken,  
I did'em that way for YEARS!  
 
Peter S
 
7/26/2000 6:15 PM
R.G.
quote:
"all of the old literature i've read has said to connect chassis ground and signal ground right AT the input jack."
 
I probably read the original poster's comments wrong. I was thinking he wanted to know how to safety ground the chassis.  
 
There are two grounds to be worried about, safety ground and signal ground. They should only touch at one point so that no circulating currents are possible. This can be the input jack, or it can be some other place, like the star ground point if you insulate the input jack.  
 
Safety ground to an aluminum chassis absolutely needs a bolted star washer connection to ensure that over time the safety ground doesn't come unconnected due to oxidation.  
 
The safety ground connection to the chassis doesn't have to be the only connection to chassis for signal ground, but it is very handy to do it there, because you've already had to worry about this gas-tight connection and longevity.  
 
It's possible to duplicate the safety ground connection somewhere else for connecting signal ground to chassis, and works just as well.  
 
The input jack works well, too, but you really should put a 3/8" star washer to the chassis on the back side of the panel there. You either want your input jacks *really* connected or *really* unconnected to the chassis. I've had several emails about input jacks being loose as being the source of terrible hum in amps.
 
7/26/2000 8:27 PM
Eric H
email

quote:
", what about the odd goop/grease  
electricians have used on Al wiring to keep O2 out of the picture? I still see it sold at many home improvement stores and the like. Any  
reason it wouldn't work here?"
 
Good question, I had to use that stuff a few times working on older houses. I can't remember if it's conductive or not. The stuff I was told to put on the headlight connections of my car (to avoid moisture incursion/corrosion) is non-conductive. We used to FILL the distributors on British motorcycles with petroleum jelly so you could ride reliably in the rain. There is a conductive grease advocated by some hi-fi guys for a (more)gas-tite connection on crimp-type speaker terminals --this sounds like good stuff for that chassis connection.  
 
-Eric
 
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