" ... 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 ) ...
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 ) ...
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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" ... 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).
" ... 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).
" ... 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.
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.
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-end...24824618QQihZ019QQcategoryZ3280QQcmdZViewItem
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-end...24824618QQihZ019QQcategoryZ3280QQcmdZViewItem
Hi,
thank you FastEddy for your explanation, but i have a problem. Since i placed the ac ground on my preamp case i have a noise at the output. If i set my volume control at 0 it's OK. I concluded that my preamp amplifies the noise of the ac ground. How i can slove this problem? thank you! Maxpou
thank you FastEddy for your explanation, but i have a problem. Since i placed the ac ground on my preamp case i have a noise at the output. If i set my volume control at 0 it's OK. I concluded that my preamp amplifies the noise of the ac ground. How i can slove this problem? thank you! Maxpou
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"Esthetics?, esthetics? we don' need no stinking esthetics ..." ... just a nice sounding pre-amp.
From your picture, the first thing I noticed was that the signal cable shielding to and from the RCA connectors are attached to the chassis or the RCA connectors' shield to chassis and also, apparently, to some point on the pre-amp board. This is certainly a possible ground loop path and possible source of "hummmm". It is a good idea to isolate the input grounds (& cable shields) from the output grounds (& cable shields) = no connect ... OR ... at a single, common connection point = aka: a "start ground" on the pre-amp circuit board.
The next thing I notice is that the signal wires from the rear connectors reach a long way without shielding, clear to the front where they get switched ... I would suggest shielding these all the way from the rear to the front then back to a signal / shield / ground connection on the pre-amp ... without any connections to the chassis or power ground. The input of a pre-amp is usually where any exteranious noise enters the system ...
I also noticed a chassis connection in the middle of the box ... I would remove that and not connect it to anything ... leaving any chassis grounding connection to happen at a point where the {external?} power supply connects, or possibly to the power line cord ground (third wire?).
From your picture, the first thing I noticed was that the signal cable shielding to and from the RCA connectors are attached to the chassis or the RCA connectors' shield to chassis and also, apparently, to some point on the pre-amp board. This is certainly a possible ground loop path and possible source of "hummmm". It is a good idea to isolate the input grounds (& cable shields) from the output grounds (& cable shields) = no connect ... OR ... at a single, common connection point = aka: a "start ground" on the pre-amp circuit board.
The next thing I notice is that the signal wires from the rear connectors reach a long way without shielding, clear to the front where they get switched ... I would suggest shielding these all the way from the rear to the front then back to a signal / shield / ground connection on the pre-amp ... without any connections to the chassis or power ground. The input of a pre-amp is usually where any exteranious noise enters the system ...
I also noticed a chassis connection in the middle of the box ... I would remove that and not connect it to anything ... leaving any chassis grounding connection to happen at a point where the {external?} power supply connects, or possibly to the power line cord ground (third wire?).
For what it's worth
Try connecting the power supply ground to a point right between (near) the output connectors (I'm assuming all of the connectors are mounted and grounded to the chassis).
Run a wire from there to the ground side of the volume control.
Run two wires from the volume control common ground (one for each channel) to the PCBs at points where the input grounds (for each channel) are located.
Cut any common connections between the two channels on the PCB and let those two ground wires be the only connection to the two circuits.
I've done this many times and it results in a dead quiet output.
Regards, Mike
Try connecting the power supply ground to a point right between (near) the output connectors (I'm assuming all of the connectors are mounted and grounded to the chassis).
Run a wire from there to the ground side of the volume control.
Run two wires from the volume control common ground (one for each channel) to the PCBs at points where the input grounds (for each channel) are located.
Cut any common connections between the two channels on the PCB and let those two ground wires be the only connection to the two circuits.
I've done this many times and it results in a dead quiet output.
Regards, Mike
Hi Guys,
thank you for reply.
my RCA connectors (input and output) are isolated, the only ground on my case is power ground, sorry because on my picture my ac ground is disconnected but if i put my volume control to 0, i don't have the noise. i noticed too when i disconnect input on my volume control and up volume, i have noise and if i disconnect ac ground i have less noise. thank you maxpou
thank you for reply.
my RCA connectors (input and output) are isolated, the only ground on my case is power ground, sorry because on my picture my ac ground is disconnected but if i put my volume control to 0, i don't have the noise. i noticed too when i disconnect input on my volume control and up volume, i have noise and if i disconnect ac ground i have less noise. thank you maxpou
Hi,
when the volume control is maximum the source impedance directly loads the input of the pre-amp.
When the volume is minimum the pre-amp input sees the zero (or near zero) resistance of the volume pot.
At any other settings the pre-amp sees some of the volume pot resistance.
The noise could be due to the non zero source impedance being fed to the pre-amp.
Pre-amps are just like power amps, they both like a low, non varying impedance on the input.
Is post 11 the schematic?
Would the 1M0 be a clue?
How is this pre-amp powered? Batteries/rectified mains?
when the volume control is maximum the source impedance directly loads the input of the pre-amp.
When the volume is minimum the pre-amp input sees the zero (or near zero) resistance of the volume pot.
At any other settings the pre-amp sees some of the volume pot resistance.
The noise could be due to the non zero source impedance being fed to the pre-amp.
Pre-amps are just like power amps, they both like a low, non varying impedance on the input.
Is post 11 the schematic?
Would the 1M0 be a clue?
How is this pre-amp powered? Batteries/rectified mains?
I experienced the issue you describe with the pot in middle settings. Mine was a buzzing noise and was at maximum level when the pot was central. As I hoped this problem completely dissapeared when said pot was placed in a metal box connected to circuit ground. You may have a shielding issue here, don't know if this helps as all
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