Hi Stefan
The reason for a ground loop is because your preamp and one of your channels do not share a proper ground, the only connection between the two is through the shield or ground wire connecting the two.
First you have to create a power ground. This would be the point where the two filter capacitors meet.
Then you create a signal ground. This would be the point where input grounds are tied together. This should be insulated from chassis.
Then you create an output ground. This would obviously where the speakers take their ground connection from.
Using heavy guage wire, connect all the above grounds for both channels to one point. This would be the CSG (Central Star Ground) of the amplifier.
Now this point should be connected to the chassis using a 10 ohm resistor and 1 uF high voltage capacitor (in parallel with each other).
I really can't get clearer than this. Hope it helps you.
The second source of hum would be the transformers inducing hum into the signal area. A bit of clean up in your wiring will help, but I've seen (and done) worse without that creating any major problems.
You do not need to run a regulated supply for power amplifiers. That's a misconception and can create more problems than it solves unless it's well thought through. So don't worry about it.
The reason for a ground loop is because your preamp and one of your channels do not share a proper ground, the only connection between the two is through the shield or ground wire connecting the two.
First you have to create a power ground. This would be the point where the two filter capacitors meet.
Then you create a signal ground. This would be the point where input grounds are tied together. This should be insulated from chassis.
Then you create an output ground. This would obviously where the speakers take their ground connection from.
Using heavy guage wire, connect all the above grounds for both channels to one point. This would be the CSG (Central Star Ground) of the amplifier.
Now this point should be connected to the chassis using a 10 ohm resistor and 1 uF high voltage capacitor (in parallel with each other).
I really can't get clearer than this. Hope it helps you.
The second source of hum would be the transformers inducing hum into the signal area. A bit of clean up in your wiring will help, but I've seen (and done) worse without that creating any major problems.
You do not need to run a regulated supply for power amplifiers. That's a misconception and can create more problems than it solves unless it's well thought through. So don't worry about it.
Two more things:
At no point should any of the input jacks be connected to the chassis. This is important to eliminate any ground loops
Also the reason for a ground loop creating hum is the voltage differential between the electrical input of the amplifier and the physical resistance of the electrical path leading to it, multiplied by the gain of the amp. This is why we are striving to create the lowest possible resistance between the input and output grounds.
At no point should any of the input jacks be connected to the chassis. This is important to eliminate any ground loops
Also the reason for a ground loop creating hum is the voltage differential between the electrical input of the amplifier and the physical resistance of the electrical path leading to it, multiplied by the gain of the amp. This is why we are striving to create the lowest possible resistance between the input and output grounds.
For the preamp...
Apart from regulating the dc voltage, the regulators like LM317, LM337 from National, with a small cap at the adj pin, drastically reduce the ripple at the output. The humming noise which u hear could be from power supply also.
If the hum is due to close proximity of the transformer, then try moving the transformer away from the ckt. If this reduces the hum, u have to shield the trannys, may be u should make a separate cabin for them.
Gajanan Phadte
Apart from regulating the dc voltage, the regulators like LM317, LM337 from National, with a small cap at the adj pin, drastically reduce the ripple at the output. The humming noise which u hear could be from power supply also.
If the hum is due to close proximity of the transformer, then try moving the transformer away from the ckt. If this reduces the hum, u have to shield the trannys, may be u should make a separate cabin for them.
Gajanan Phadte
HI GUYSSSS.....
YOUR PROBABLY WONDERING WHY I AM WRITING IN CAPS LOCK WELLLLLLLLL MY AMP WORKSSSSSSS
YOU WONT BELEIVE how easy the fix was there was nothing really wrong with the ground, well there was but it was a simple cable I had to make from the GROUND of the INPUT of the pre-amp and the cable goes accross to the OUTPUT GROUND. THATS IT NO hum what so ever, I only done it as a guess.
I am sooo HAPPY lol, and I would LOVE to THANK EVERYONE for helping me out, without you guys I probably wouldnt have even looked at ground as a problem , SOOOO THANK YOU soo much everyone. Your all great people...
If you would like more info on how it works just ask.
I will be glad to tell anyone of what I just done lol ( I arent a geneus this was just a TOTAL guess )
THANKS ALOT
STEFAN
YOUR PROBABLY WONDERING WHY I AM WRITING IN CAPS LOCK WELLLLLLLLL MY AMP WORKSSSSSSS
YOU WONT BELEIVE how easy the fix was there was nothing really wrong with the ground, well there was but it was a simple cable I had to make from the GROUND of the INPUT of the pre-amp and the cable goes accross to the OUTPUT GROUND. THATS IT NO hum what so ever, I only done it as a guess.
I am sooo HAPPY lol, and I would LOVE to THANK EVERYONE for helping me out, without you guys I probably wouldnt have even looked at ground as a problem , SOOOO THANK YOU soo much everyone. Your all great people...
If you would like more info on how it works just ask.
I will be glad to tell anyone of what I just done lol ( I arent a geneus this was just a TOTAL guess )
THANKS ALOT
STEFAN
Hi,
Welll I dont know cause I noticed that the power and signal ground on the pre map were all connected as one, but when I attched a cable from pre amp input to the pre amp output it made it all better,
The pre amp did have a ground but when it touched the case it made a terrible sound.
Thanks
STefan
Welll I dont know cause I noticed that the power and signal ground on the pre map were all connected as one, but when I attched a cable from pre amp input to the pre amp output it made it all better,
The pre amp did have a ground but when it touched the case it made a terrible sound.
Thanks
STefan
power amp humming
dear friend's please help me when my amplifier input wire connect to ground or volume controller full trun off the humming sound allways came out from the speaker . when my amplifier input float then no humming . my amplifier run dual power supply . what happend dear ? please help me
dear friend's please help me when my amplifier input wire connect to ground or volume controller full trun off the humming sound allways came out from the speaker . when my amplifier input float then no humming . my amplifier run dual power supply . what happend dear ? please help me
I upload my audio amplifier protection board . When my protection board first start audio output wire is connected to the ground and cheaking everything . When everythig was ok then audio output are connected to the audio input terminal through dpdt relay . Problem was that first time when audio output was connected to the ground then create a noice . When audio output terminal connected to the ground through dpdt relay why create the humming noice ? Here audio input terminal is connect to preamp and audio output terminal connect to the power input.
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