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Old 25th April 2007, 11:35 PM   #1
maxpou is offline maxpou  Canada
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Question How placed the ground in my amp

Hi everybody,
i have a little question for you. i would like to know how placed the ground in my amp? I have power supply for each channel in 1 aluminium case Thus I have 3 grounds in 1 case and if I joint them together I have a hum in my loudspeaker. Thank you! Maxpou
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Old 27th April 2007, 06:44 PM   #2
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Have you tried to ground each amp to its perspective power supply.A photo or schematic of you project would be useful.

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Old 27th April 2007, 07:08 PM   #3
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" ... Have you tried to ground each amp to its perspective power supply. ..." ?

Yes. This is important. Each amp / power supply combination should have its own separate ground scenario and be completely separate from the other amp/PS ... AND the metal chassis ground. There are ways to tie these all together, but it is difficult without generating "ground loops" ... as you have discovered. ( http://en.wikipedia.org/wiki/Ground_loop ) ...
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Old 28th April 2007, 05:31 AM   #4
maxpou is offline maxpou  Canada
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Default Schematic wire gnd

Hi Guys,
thank you for your reply i send you a schematic wire gnd. i would like to know how i place PS gnd and AC gnd. Thank You! maxpou
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File Type: jpg schema poweramp.jpg (41.5 KB, 648 views)
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Old 28th April 2007, 05:41 AM   #5
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An important consideration, so one reads, is NOT to bring the ground points back to where you tie the filter caps together. Suppossedly there is a lot localized noise right there. Instead use a location 3-4 inches away from the caps.
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Old 28th April 2007, 06:06 AM   #6
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Quote:
An important consideration, so one reads, is NOT to bring the ground points back to where you tie the filter caps together. Suppossedly there is a lot localized noise right there. Instead use a location 3-4 inches away from the caps.
I'll have to disagree.Take a little time and read this article.I did and I built two ESP P101 2-channel amps with absolutely no hum.Period!The first try!
http://www.sound.westhost.com/psu-wiring.htm

Notice all grounds are routed directly to the copper buss plate"star ground" on the filter caps.


Dave
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Old 28th April 2007, 04:06 PM   #7
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" ... An important consideration, so one reads, is NOT to bring the ground points back to where you tie the filter caps together. ..."

" ... Notice all grounds are routed directly to the copper buss plate"star ground" on the filter caps. ..."

Both are correct here: The similarities lie with the use of a single, common, "star" ground point. And this is as it should be in all cases.

Maxpou's diagram shows double (parallel) ground lines running from inputs to amp boards and on to the PSU ground point with ground paths directly from the PSU back to the amp for an additional power ground path ...

IMOP: ground the inputs and outputs to a single point on the amp boards, only. Remove the additional ground paths from signal I/O back to the ground on the PSU ... OR ... Attach all grounds at the single ground point of the PSU (ala XEagleKeeper's picture) ... BUT not both.

As for the resistor value, you might try an inffinate value first = no resistor at all = the chassis is not connected to any point of the PSUs or the amp boards (but the chassis is connected to the ground of the power cord).
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Old 6th June 2007, 04:35 PM   #8
maxpou is offline maxpou  Canada
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Hi Guys,
i have a pre-amp in 2 cases separate, PSU and pre-amp. I would like to know how placed my ground? Thank You! Maxpou
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Old 6th June 2007, 06:02 PM   #9
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" ... 2 cases separate, PSU and pre-amp. I would like to know how placed my ground? ..."

Assuming you mean between the PS unit chassis and the separate Pre-amp unit chassis.

IMOP I would run three healthy low resistant cables, one each for + / - / gnd. Assuming power is less than ~ 100 watts, I would use fine stranded #18 or #16 gauge with teflon insulation. If you can find fine strand silver or silver plated copper wire, so much the better. I might also suggest three or four conductor cable with a shield, also with teflon insulation (at least on the conductors) and a suitable audio quality connector set. As per the above suggestions, I would not run more than one single ground connection between the two boxes, terminating the cable shield at one end only, preferably at the power supply box connection ... and I would make sure that this audio ground wire does not connect to the chassis ground or cable shield of either box ... thus reducing the possiblities of ground loops.
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Old 6th June 2007, 06:03 PM   #10
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Default one point eart grounding, never do earth grounding more than 2 point

please do one point earth grounding only, never take ground point >. more than 2 pointS, to do star grounding is better, please see star grounding, I SAW SOME STAR GROUNDINGS ON INTERNET:

http://cgi.ebay.com/300b-single-ende...QQcmdZViewItem
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