BP/PS supplies - get ground from where? - diyAudio
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Old 28th April 2010, 10:01 PM   #1
phrarod is offline phrarod  United States
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Default BP/PS supplies - get ground from where?

While I'm waiting to upgrade to the new shunt from you guys I'm trying to redo the grounding scheme and lower my hum levels. I have a tube output in the same chassis although its ps is in another chassis.

Both chassis share the same chassis ground (connected by wire in the cable). I want to separate the digital grounds from the analog/signal grounds. I notice if I lift all the digital grounds to the AN dac board I still get reference to chassis ground coming from the Twisted Pear boards. All I can think is they're getting the ground chassis reference from the Torodials I purchased from you. I've never worked with Torodials before so I can't see with 2 wires to AC and two to the boards how they can get chassis ground reference. I have the trans mounted to the chassis using the hardware that came with it. Since there's no center tap or shield -- what am I missing?

Essentially I wanted to try to float the digital grounds to see if I can get less hum.
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Old 29th April 2010, 02:41 AM   #2
phrarod is offline phrarod  United States
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ok, I found the issue after a lot of measuring. It was on the dac board. When I screw down the I/V's it makes chassis ground from the standoff. This doesn't make any sense until I realized I used the lead that also grounds the MuMetal can and put it to ground star grounds presently not connected to anything. I used plastic screws and its solved to chassis ground issue..

However, I have a couple questions.

I'm wondering of I should remove that can ground because shields shouldn't go to floating grounds as I understand it. Problem is what I just found so its either not use it or give up on the idea of floating the digital.

Since the power supplies do not see any earth ground until the hit the digital board is it ok to float this whole star ground?

I would wind up with two 'stars' one floated for the analog and a second floated for the digital which are all connected back to the chassis ground coming in from the ps box.

Just trying to drop hum to as low as possible....
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Old 5th May 2010, 02:05 AM   #3
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It is perfectly fine to float the whole thing.
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Old 5th May 2010, 03:03 AM   #4
phrarod is offline phrarod  United States
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Thanks Russ. I did and reduced him by 85% or better. Now I'm greedy.

My dac board has Analog out grounds which my i/v use. I have the i/v secondary grounded to my analog grounds but the input are the board's which are floated with the rest of the digital. Do you think I should move those grounds to the analog?
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