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Issue on a new (for me) AU-666

Alexeifox

Alexeifox

New Member
First of all hello and good morning everyone!

i bought this amplifier a couple days ago in great condition and it really sounds amazing other than the fact that there is some extremely strange things going on inside.

When no input is plugged in everything is dead silent, but the moment i plug any kind of device into it, some strange buzz comes up, not a constant buzz but a strange pulsating buzz, like it was someone repeatedly pressing an obnoxious synthesizer key, if Aux, for example, is plugged into my pc, this buzz is present on all inputs and even louder in Phono ins.

The noise is present even when the volume is turned all the way down and doesnt respond to any preamp controls (but pre out does show the issue, seems its not a power amplifier problem), i tried plugging everything into the same plug but nothing has changed which makes me discard a ground loop.

If someone has some clue on what may be causing this it would be saving me a heavy headache, Thanks!
 
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Alexeifox said:
but the moment i plug any kind of device into it, some strange buzz comes up, not a constant buzz but a strange pulsating buzz, like it was someone repeatedly pressing an obnoxious synthesizer key, if Aux, for example, is plugged into my pc, this buzz is present on all inputs and even louder in Phono ins.
Click to expand...

•What device are you plugging in?
•Best only to ever plug a turntable into the plono jacks.
•With nothing plugged in, and speakers connected, do you hear any of the issues coming through, even when increasing the volume?
 
If it's on both channels and not affected by the volume control, I think it would be a power supply issue, but you said there's only a buzz when something is plugged into it?
 
AnalogueBen said:
Try plugging something other than a PC or Cell Phone.
Try something analogue, do you have a tape deck, CD player or a turntable to connect?
Click to expand...
Alright so tried this and im getting some clues, my turntable plays well if its the only thing plugged into the amp, if i plug my phone into aux, no noise happens, but the moment i plug it into my pc, the noise begins again. i connected my headphones directly to the pc out and the noise is not there, nor in another headphone amp i pluged into it, could it be the pc ground looping? it would be a pretty unusual ground loop noise
 
AnalogueBen said:
•What device are you plugging in?
•Best only to ever plug a turntable into the plono jacks.
•With nothing plugged in, and speakers connected, do you hear any of the issues coming through, even when increasing the volume?
Click to expand...
both Pc and turntable, each into their respective inputs (edited for typing error)
 
Bruno Primas said:
If it's on both channels and not affected by the volume control, I think it would be a power supply issue, but you said there's only a buzz when something is plugged into it?
Click to expand...
i did also think it was a psu problem at first, but now if i plug the TT exclusively it plays dead silent (and pretty wonderfully i must say, this is my first sansui and definetly not the last) Seems the amplifier is allergic to my computer!
 
Bruno Primas said:
Is the computer located on the same side of the Sansui's transformer? Is it sitting too close?
Click to expand...
tried placing it next to the pc, on the other end of the desk (mind its a 5 foot desk) and i have heard no changes, i have no clue on how to upload an audio clip i recorded of it in case it might help, and, for real guys, all this help is deeply appreciated!
 
Bruno Primas said:
Is the PC plugged in to the amp when you hear the sound when using your phone?

Is the PC using the same outlet as the amp?
Click to expand...
If the pc is plugged in every input will have the sound regardless of what in is selected, I tried the pc in the same outlet as the amp, in different outs and even in a regulator and it’s the same in all cases.

Im coming across new things, just the fact of having an rca plugged into the aux in (even if the cable is unplugged on the other end) will create the noise for the phono input even if there is no turntable plugged into phono.

this really has me scratching my head
 
Seems the only way I can listen to things now is through my phone, plugging the same cable into the pc makes the noise, phono stage has the noise just because there is an rca in aux
 
If I plug a 3.5mm to RCA jacks cord into a amp, without it being plugged into anything, (like my phone), it will buzz. There has got to be a ground issue. I wonder what would happen if you ran a wire from a metal point on your computer to the ground on the amp like a ground wire on a turntable? Would it quiet it down?
 
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