I get a hum through my speakers and loud enough to hear it from a few feet away. when trying to isolate the problem it happens the same with sources hooked up or nothing hooked up except the speakers. its not a 60 cycle problem because my other amps are totally quiet. I'm thinking it could be the toroidal transformer. one thing I'm considering is to wrap it with mu shielding tape and wanted to know if any of you have had this problem and tried this with any success. thanks for any info.
is the amp commercially built?
How old is it?
Do you know it's history? Has it been dropped/damaged?
How old is it?
Do you know it's history? Has it been dropped/damaged?
hi Andrew T,
it is a known company built integrated amp about seven years old. it doesn't appear damaged at all and I took a look inside and everything looks good to my eyes. I did talk with the designer and he said to see if orienting (turning it) the toroidal transformer might reduce the hum but that didn't work. there's not much room to turn it because the wiring has hardly any slack. one thing I noticed is its right up against the mains wiring which is covered with a rubber boot. just seems like it should have been isolated from everything more than it is.
it is a known company built integrated amp about seven years old. it doesn't appear damaged at all and I took a look inside and everything looks good to my eyes. I did talk with the designer and he said to see if orienting (turning it) the toroidal transformer might reduce the hum but that didn't work. there's not much room to turn it because the wiring has hardly any slack. one thing I noticed is its right up against the mains wiring which is covered with a rubber boot. just seems like it should have been isolated from everything more than it is.
Hi DF96,
I would say its 60Hz hum. it is more of a "rounded" tone if you will, not like a ground loop hum which is more "static" sounding?
I would say its 60Hz hum. it is more of a "rounded" tone if you will, not like a ground loop hum which is more "static" sounding?
Ground loop hum is often 60Hz. Don't confuse the fundamental with the presence or absence of harmonics.
Put your finger on an input connection. Turn up the volume until you can hear the hum from your finger. Is this the same frequency? 'Finger hum' is likely to be mainly 60Hz.
Does the hum you are trying to fix vary with the volume setting?
Put your finger on an input connection. Turn up the volume until you can hear the hum from your finger. Is this the same frequency? 'Finger hum' is likely to be mainly 60Hz.
Does the hum you are trying to fix vary with the volume setting?
Hi DF96,
no change at all trying the finger method and also no change at different volumes even all the way up.
no change at all trying the finger method and also no change at different volumes even all the way up.
That result is very unusual.
An open input is a very good pick up for interference and one of the biggest interference sources is the mains cabling around the house.
Adding a finger to the Hot side of an Input usually produces a bit of hum with the vol pot at a lowish setting. With vol pot at maximum I would expect an almost deafening hum !
I wonder if the input wiring has a break. That might result in excessive hum at the speaker for a not well screened chassis.
this integrated has a great reputation but I'm surprised at the layout. like I said before the toroidal transformer is touching the mains wires and another thing is that the right speaker connections are also real close to the mains. I don't know if this would have anything to do with it or not. I will inspect the wiring for a break.
It might help if you told us what it is. Someone on here may have one and know exactly how to fix it.
I have experimented in a very amateurish way to try to find a susceptibility for mains hum to get into low level wiring/interconnects.
I tried moving a long interconnect around and over and under the mains transformer while it was all powered on. I could not hear any effect at the speaker.
The hum did not seem to affect the twisted pair interconnect at all.
I would expect the speaker wiring to be even more tolerant of hum fields.
I would expect the mains wiring to be completely tolerant of the fields emitted by the mains transformer.
I also moved the music carrying interconnect around and over the active PCB and again I could not hear any changes.
I tried moving a long interconnect around and over and under the mains transformer while it was all powered on. I could not hear any effect at the speaker.
The hum did not seem to affect the twisted pair interconnect at all.
I would expect the speaker wiring to be even more tolerant of hum fields.
I would expect the mains wiring to be completely tolerant of the fields emitted by the mains transformer.
I also moved the music carrying interconnect around and over the active PCB and again I could not hear any changes.
BTW,
the long interconnect in that experiment of post11 was not a coaxial cable, it was an unscreened star quad into a +28dB gain power amplifier driving 8ohms speakers.
I repeated with a simple unscreened twisted pair. Again no audible change.
the long interconnect in that experiment of post11 was not a coaxial cable, it was an unscreened star quad into a +28dB gain power amplifier driving 8ohms speakers.
I repeated with a simple unscreened twisted pair. Again no audible change.
my apologies, I went back and tried the finger test again touching both ends of my interconnects and indeed I got a buzz and it did get louder when turning it up. this buzz is just like my guitar amp when I'm playing a single coil guitar, totally different from the hum I'm trying to eliminate which still sounds the same even if I turn it up or down with no change in volume hope this helps.
Last edited:
Short the input using a dummy plug with zero ohms across the Hot Cold terminals.
Now measure the output Hum + Noise. It should be <1.0mVac and better if it is 0.1mVac or less.
Now measure the output Hum + Noise. It should be <1.0mVac and better if it is 0.1mVac or less.
well I have no measuring equipment so that is out but thanks for the suggestion. now here is one thing I discovered, the hum went down in volume as the day progressed. but it was just as loud again in the evening. could this have anything to do with the electrical grid usage?
Yes, but that usually comes through as mechanical hum direct from the vibrating transformer. Sometimes amplified by a resonant chassis.
Hum through the speakers is an electrical hum.
That is more likely to be due to a wiring fault or due to electrolytic capacitors that are well beyond their "best by" date. If electros are kept cool you can often get more than 20years out of them.
Hum through the speakers is an electrical hum.
That is more likely to be due to a wiring fault or due to electrolytic capacitors that are well beyond their "best by" date. If electros are kept cool you can often get more than 20years out of them.
this amp does get pretty hot when played. it has no vents and the heat sinks are screwed into the sides of the chassis.
since you do not have a multimeter (basic).. plug you amp in another room(outlet) and see if hum is lower.
hi lanchile, yep I have already done that. its the same anywhere I have tried it including my Son's home.
- Status
- Not open for further replies.