Subwoofer humming
 

Hi,

Home-made 10" subwoofer unit, connected to Kenwood AV-Receiver model
KRF-7050D. it has it's own PS and internal, DIY 2x10W amp kit.
When i turn on the power, the unit produces a loud hum, and after about 2
sec. the hum is quiet but still present. when i mute my receiver, the hum
goes away, so i suspected the input is bad. the thing has proper grounding.
i replaced the PS, as i thought it inserts hum into the system, but no good.
after checking the amp there were some loosen electrolytic caps (cold
solder), which i re-soldered (i have this amp for about 12 years or so). i
soldered another electrolytic cap to the input side of the amp (100uF, 10v)
and tested it - now the hum is gone completely, but along with the hum went
the sound it should produce.

anything else i should check? / i've done wrong ?

"Michael Rabeno" wrote in message
...
Hi,

Home-made 10" subwoofer unit, connected to Kenwood AV-Receiver model
KRF-7050D. it has it's own PS and internal, DIY 2x10W amp kit.
When i turn on the power, the unit produces a loud hum, and after about 2
sec. the hum is quiet but still present. when i mute my receiver, the hum
goes away, so i suspected the input is bad. the thing has proper
grounding.
i replaced the PS, as i thought it inserts hum into the system, but no
good.
after checking the amp there were some loosen electrolytic caps (cold
solder), which i re-soldered (i have this amp for about 12 years or so). i
soldered another electrolytic cap to the input side of the amp (100uF,
10v)
and tested it - now the hum is gone completely, but along with the hum
went
the sound it should produce.

anything else i should check? / i've done wrong ?



1: teach the subwoofer the lyrics or

2: use shielded cables to the input

"Michael Rabeno" wrote in message
...
Hi,

Home-made 10" subwoofer unit, connected to Kenwood AV-Receiver model
KRF-7050D. it has it's own PS and internal, DIY 2x10W amp kit.
When i turn on the power, the unit produces a loud hum, and after about 2
sec. the hum is quiet but still present. when i mute my receiver, the hum
goes away, so i suspected the input is bad. the thing has proper
grounding.
i replaced the PS, as i thought it inserts hum into the system, but no
good.
after checking the amp there were some loosen electrolytic caps (cold
solder), which i re-soldered (i have this amp for about 12 years or so). i
soldered another electrolytic cap to the input side of the amp (100uF,
10v)
and tested it - now the hum is gone completely, but along with the hum
went
the sound it should produce.

anything else i should check? / i've done wrong ?



Sounds like a ground loop, are both the sub and the reciever plugged into
the same outlet?

On Fri, 15 Oct 2004 16:24:45 +0200 "Michael Rabeno"
wrote:

Hi,

Home-made 10" subwoofer unit, connected to Kenwood AV-Receiver model
KRF-7050D. it has it's own PS and internal, DIY 2x10W amp kit.
When i turn on the power, the unit produces a loud hum, and after about 2
sec. the hum is quiet but still present. when i mute my receiver, the hum
goes away, so i suspected the input is bad. the thing has proper grounding.
i replaced the PS, as i thought it inserts hum into the system, but no good.
after checking the amp there were some loosen electrolytic caps (cold
solder), which i re-soldered (i have this amp for about 12 years or so). i
soldered another electrolytic cap to the input side of the amp (100uF, 10v)
and tested it - now the hum is gone completely, but along with the hum went
the sound it should produce.

anything else i should check? / i've done wrong ?

Did you by any chance resolder the caps while the amp was powered up,
or when the caps were still charged?

If so, you probably blew something up when you reached in there with a
grounded soldering iron.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

yes they are. actually the sub is fed from the controlled outlet on the
receiver, so the sub won't always be on, but only when i'm using the sound
system.

"James Sweet" wrote in message
news:Cj%bd.71$5l3.42@trnddc02...

"Michael Rabeno" wrote in message
...
Hi,

Home-made 10" subwoofer unit, connected to Kenwood AV-Receiver model
KRF-7050D. it has it's own PS and internal, DIY 2x10W amp kit.
When i turn on the power, the unit produces a loud hum, and after about 2
sec. the hum is quiet but still present. when i mute my receiver, the hum
goes away, so i suspected the input is bad. the thing has proper
grounding.
i replaced the PS, as i thought it inserts hum into the system, but no
good.
after checking the amp there were some loosen electrolytic caps (cold
solder), which i re-soldered (i have this amp for about 12 years or so).
i
soldered another electrolytic cap to the input side of the amp (100uF,
10v)
and tested it - now the hum is gone completely, but along with the hum
went
the sound it should produce.

anything else i should check? / i've done wrong ?



Sounds like a ground loop, are both the sub and the reciever plugged into
the same outlet?

no. i waited for the caps to discharge before i re-soldered them. anyway,
the amp is still working so i don't think something was blowen up.

"Jim Adney" wrote in message
...
On Fri, 15 Oct 2004 16:24:45 +0200 "Michael Rabeno"
wrote:

Hi,

Home-made 10" subwoofer unit, connected to Kenwood AV-Receiver model
KRF-7050D. it has it's own PS and internal, DIY 2x10W amp kit.
When i turn on the power, the unit produces a loud hum, and after about 2
sec. the hum is quiet but still present. when i mute my receiver, the hum
goes away, so i suspected the input is bad. the thing has proper
grounding.
i replaced the PS, as i thought it inserts hum into the system, but no
good.
after checking the amp there were some loosen electrolytic caps (cold
solder), which i re-soldered (i have this amp for about 12 years or so). i
soldered another electrolytic cap to the input side of the amp (100uF,
10v)
and tested it - now the hum is gone completely, but along with the hum
went
the sound it should produce.

anything else i should check? / i've done wrong ?

Did you by any chance resolder the caps while the amp was powered up,
or when the caps were still charged?

If so, you probably blew something up when you reached in there with a
grounded soldering iron.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------