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Ground Bus question
Ground Bus question
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Old 15th September 2020, 09:57 AM   #1
spoontex is offline spoontex  Spain
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Default Ground Bus question

Hi,


I'm planning to build my first tube amp with Tag Strip boards. But I have a question about ground bus bar and ground loops. If I mount some tag stripes board, and one of the tag goes to chassis with a screw and I solder the bus bar... this is a ground loop?


Thanks.
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Old 15th September 2020, 10:15 AM   #2
TonyTecson is offline TonyTecson  Philippines
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you can make a ground buss and connect everything that needs grounding there, and the ground bus need not even connect to chassis, i use platic casings in some of my builds....
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Old 15th September 2020, 04:02 PM   #3
Palustris is offline Palustris  United States
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Yes, if you use that tag as a ground and do the same with another tag strip you have a loop. I always bend that tag over the strip and crimp with pliers it to ensure that I don't use it as a ground by mistake. Once you fold over that tab, the tag strip becomes stronger and you can add a dab of epoxy to the joint if you want it really secure.
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Old 15th September 2020, 04:12 PM   #4
spoontex is offline spoontex  Spain
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Yes. That was I always thinking. But I have a tube book that the author uses this way.

Look at that.
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Old 15th September 2020, 04:49 PM   #5
baudouin0 is offline baudouin0
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The main thing to make sure is that you return the rectifier currents straight back to the transformer so they don't enter your signal ground.
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Old 15th September 2020, 05:57 PM   #6
nigelwright7557 is offline nigelwright7557  United Kingdom
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As above^^^
The power supply wire as should be serialised.
That is in one side and out the other and no mixing with audio grounds.
Audio grounds should be star grounded.
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Old 15th September 2020, 06:03 PM   #7
rayma is offline rayma  United States
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Quote:
Originally Posted by spoontex View Post
But I have a tube book that the author uses this way.
That is commonly done, and is convenient, but is not the best way. Often they use grounded lugs
at multiple locations, which guarantees ground loops.

Last edited by rayma; 15th September 2020 at 06:06 PM.
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Old 16th September 2020, 02:03 AM   #8
Tom Bavis is offline Tom Bavis
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It's only a ground loop if current is flowing in the chassis where you don't want it. Get the power supply right (adequate filtering, no capacitor ripple current through the chassis, no heater current in the chassis) and you can ground anything else anywhere and be completely hum-free. Look at any 50's - 60's hi-fi construction - they knew how to do it. Star ground and bus can have hum-producing loops if not implemented correctly - keep current loops short!
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Old 16th September 2020, 08:44 AM   #9
6A3sUMMER is offline 6A3sUMMER  United States
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1. Connect the B+ secondary center tap to the very first filter cap.
Then connect from the very first filter cap to the second filter cap.
Then connect from the second filter cap to the amplifier central ground point.

2. Do not connect the B+ secondary center tap directly to the amplifier central ground point.

A little drawing of these two, and a little thought will show you one of the best and worst
ways to wire the amp.

The first (1) keeps the high frequency transient currents in a local loop.

The second (2) puts the transient currents onto the rest of the amplifier.
That IS a very bad ground loop.

Now you know something about ground loops.
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Old 16th September 2020, 09:15 AM   #10
TonyTecson is offline TonyTecson  Philippines
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my design guidelines....

1. every power lead has its own return wire to the psu, preferably twisted pair..
2. do not rely on power supply negative return lead to run signal returns.
3. signal wires should have its own returns wire to psu ground..
4. designate a ground buss where all items that need to be at zero volts are all soldered in...this ground buss need not connect to the chassis metal work.
5. you can if you must connect the ground at a point where signal is lowest..

Last edited by TonyTecson; 16th September 2020 at 09:17 AM.
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