Grounding layout for double chasis - VBIGC - diyAudio
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Old 20th June 2004, 07:31 AM   #1
Will is offline Will  Malaysia
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Default Grounding layout for double chasis - VBIGC

What's you vote for the best possible sonics/stability given the following hardware:

1) Using Independant Tx to power the left and right channel (for LM3875)
2) Both Tx has double secondaries
3) For each Tx, use 8 sets of diodes
4) Tx are in a separate chasis from the amplifier


Now, how would you layout the grounding ?
a) AC power chord with earth connected to Tx chasis; Both Tx gnd connected to chasis; Rectifiers output voltage + ground wire from both sets of Tx connected to umbilical chord (i.e. 5 sets of wire going to amplifier)

b) AC power chord with earth connected to Tx chasis; Both Tx gnd NOT connected to chasis; Rectifiers output voltage + ground wire from both sets of Tx connected to umbilical chord (i.e. 5 sets of wire going to amplifier)

c) AC power chord with earth connected to Tx chasis; Tx output voltage from both sets of Tx connected to umbilical chord (i.e. 8 sets of wire going to amplifier unrectified);



regards,
will.
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Old 20th June 2004, 07:43 AM   #2
Nuuk is offline Nuuk  United Kingdom
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AFAIK, newer transformers are not connected to the chassis.

If you care to be more specific as to how you want to house your transformers and amp circuits, it should be possible to advise you on the grounding arrangements.
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Old 20th June 2004, 07:48 AM   #3
Will is offline Will  Malaysia
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Ok, perhaps the term "Both Tx gnd connected to chasis" is a little vague. Specifically they would mean connecting the ground wire after rectification to chasis ground, and that same ground wire will be connected to the umbilical chord going to the amplifier.
Make sense ?

regards
will.
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Old 20th June 2004, 08:15 AM   #4
Nuuk is offline Nuuk  United Kingdom
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Will, you seem to be confused bvetween the 0 (zero) volt rail and the earth connection (don't worry, many people are).

The 0 v wire runs from the PSU to the power ground star on the amp.

If you have a metal chassis or shilding on the amp case, a separate wire is taken from the mains earth connection (in the PSU case) to the chassis or shielding (of the amp case). The point that is connected to is then joined to the power ground star via a cap and resistor in series.

Take a look at the grounding arrangement shown on the GC FAQ page at Decibel Dungeon.
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Old 20th June 2004, 08:29 AM   #5
Will is offline Will  Malaysia
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Cheers for that Nick. Yep I definately got that mixed up.
Now assuming the confusion is all cleared up, which of the setup would seem better, i.e.
1) Rectify in the PSU casing without caps - umbilical chord sending unsmoothen DC
2) Rectify in the Amp casing with caps in close proximity

Does it make sense to connect the zero volt of both Tx together and then supply as one in the umbilical chord ? Any takers ?

regards,
will.
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Old 20th June 2004, 08:50 AM   #6
Nuuk is offline Nuuk  United Kingdom
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My advice is to keep the transformers in a separate case, run the supplies from each transformer (after the rectifier bridge and small caps (say 100 uF) through umboilicals to each amplifier circuit.

In one umbilical include an earth wire connected as above.

If you are using two transformers then keep the PSU's separate.
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