O.K. Here's the problem.....
After listening to my G.C.'s happily for a while I put the guts in new cases. Now when I connect the amps to pre-amp I get buzz from the speakers, even with no sources connected. I've tried grounding everything. Funny thing is that if I pull one I.C. the buzz goes away and one channel is fine. If I disconnect power from G.C.'s , no buzz... but of course no music either.
I can't figure out if it's power supply, gainclones, or pre....
Any advice would be appreciated.
Jamie
After listening to my G.C.'s happily for a while I put the guts in new cases. Now when I connect the amps to pre-amp I get buzz from the speakers, even with no sources connected. I've tried grounding everything. Funny thing is that if I pull one I.C. the buzz goes away and one channel is fine. If I disconnect power from G.C.'s , no buzz... but of course no music either.
I can't figure out if it's power supply, gainclones, or pre....
Any advice would be appreciated.
Jamie
Typical of people testing only one channel each time before making the amp and fitting the whole thing in the box.
I said this a million trillion times, but here it goes again:
With ONE tranformer for both channels you MUST have the two chips close from each other.
Run a thick wire, as short as possible, from the power ground of one chip to the power ground of the other chip.
On the middle point of that wire solder the ground cable that comes from the PSU.
No HUM!
I said this a million trillion times, but here it goes again:
With ONE tranformer for both channels you MUST have the two chips close from each other.
Run a thick wire, as short as possible, from the power ground of one chip to the power ground of the other chip.
On the middle point of that wire solder the ground cable that comes from the PSU.
No HUM!
If Carlosfm's suggestion doesn't work, then also try your preamp with another amp and see if it is the problem. Then, connect an input directly to the amp with no preamp. Remember that the equipment producting the input signal MUST have some form of volume control (like a portable CD player) or it will be on max...
carlosfm said:Typical of people testing only one channel each time before making the amp and fitting the whole thing in the box.
I said this a million trillion times, but here it goes again:
With ONE tranformer for both channels you MUST have the two chips close from each other.
Run a thick wire, as short as possible, from the power ground of one chip to the power ground of the other chip.
On the middle point of that wire solder the ground cable that comes from the PSU.
No HUM!
Carlos, does this also apply if humming is non-existing when interconnects are not connected?
I have one transformer for two channels, and I have some small humming when I put my ear to the woofer. However if I disconnect my interconnects, the amp is dead silent with no hum at all.
I did not use your recommendation above, but seperated grounds from bridges until meet at star ground.
/Jan
2Bak said:
More reasons to think of a miswiring on the input connectors, which only gets active when you plug in an external source.
Did you check those wirings as I described above?
Why don't you try disconnecting one of the RCA grounds altogether? That is leave only the RCA end on one channel or the signal end within the amp, but only one end. That maybe the loop.
By leaving just one end connected you will still shield the signal wire but severe the ground loop.
Carlos (the other)
2Bak said:
Can you post a picture?
That may help.
It's much better to do as I said than to drive a ground cable from each channel (chip) to a star ground.
It's really a question of centimeters.
The two chips have to be close one to the other.
Absolutely no humm, with or without the source connected.
You have a ground loop there.
carlosfm said:
I join signal and pwr-ground on the main pcb with two wires as seen on the picture.
http://2bak.homepage.dk/starground.jpg
I've also tried to use a thinner wire in the right side (signal side), with no success.
Both of my gainclones has this (small) humming. I would like them to be completely silent. They are completely silent when
I unplug the interconnects.
By the way: Yesterday I was experimenting - on my two channel - with carlmarts advice above, with removing the shield in the one end of the interconnects, and the amp got silent, however when I turned up volume I heard increasing hum. I will also try this exeperiment on my 4-ch power-amp GC.
Thanks
/Jan
carlosfm said:What happens if you put a link on the RCA inputs of the amp joining the two grounds?
I think you have a ground loop the size of the interconnect cable...
Thanks Carlos, but I not quite sure I understand what you mean.
You mean connecting ground at each RCA chassis connector with a wire ? Between left and right channel?
/Jan
carlosfm said:What happens if you put a link on the RCA inputs of the amp joining the two grounds?
I think you have a ground loop the size of the interconnect cable...
Carlos, I'm still in doubt of what you mean.
Do you want me - at the RCA input connectors - to:
1. connect +ground and +ground between both channels with a wire and connect -ground and -ground between both channel with a wire
or
2. connect +ground and -ground for each channel with a wire, and keep RCA grounds seperate between left and right channels?
/Jan
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