Can't Stop Humming

[radio10]

Well, that's the thing: the house wiring is not in good shape. We moved
in here about seven or eight years ago, and did *some* re-wiring, but
the bulk of the wiring is old and leads to a lot of 60 Hz noise in
sensitive equipment. I can't do biofeedback in any room of the house
except for my office, where the wiring is new and the 60 Hz noise is
nominal. Like I said in an earlier post, this is a hundred year-old
house: in 1906 people weren't worrying about audio equipment since
there wasn't any.

Ron

Hi,

I can't help thinking that you may have a fault in the first or second
stages of the amp. What does the guitar actually sound like when
playing through it? Is it extremely distorted? or clean if only the hum
wasn't there? I have one of those little Fender Frontman 15w amps that
was very noisy but was due to one of the input stages shorted inside
the first dual op amp. It's relatively easy to blow the first stage of
preamplification by overdriving it with a guitar effects unit/pedals
etc.

Richard

 

[radio10]

Well, that's the thing: the house wiring is not in good shape. We moved
in here about seven or eight years ago, and did *some* re-wiring, but
the bulk of the wiring is old and leads to a lot of 60 Hz noise in
sensitive equipment. I can't do biofeedback in any room of the house
except for my office, where the wiring is new and the 60 Hz noise is
nominal. Like I said in an earlier post, this is a hundred year-old
house: in 1906 people weren't worrying about audio equipment since
there wasn't any.

Ron

Hi,

I can't help thinking that you may have a fault in the first or second
stages of the amp. What does the guitar actually sound like when
playing through it? Is it extremely distorted? or clean if only the hum
wasn't there? I have one of those little Fender Frontman 15w amps that
was very noisy but was due to one of the input stages shorted inside
the first dual op amp. It's relatively easy to blow the first stage of
preamplification by overdriving it with a guitar effects unit/pedals
etc.

Richard

 

[Ross Herbert]

Well, that's the thing: the house wiring is not in good shape. We moved
in here about seven or eight years ago, and did *some* re-wiring, but
the bulk of the wiring is old and leads to a lot of 60 Hz noise in
sensitive equipment. I can't do biofeedback in any room of the house
except for my office, where the wiring is new and the 60 Hz noise is
nominal. Like I said in an earlier post, this is a hundred year-old
house: in 1906 people weren't worrying about audio equipment since
there wasn't any.

Ron

Probably still some of the original black rubber and cotton insulation
wiring there I suppose. The rubber goes hard and brittle and breaks
away from the conductor thus exposing the wiring to possible shorts
and other hazards. Maybe the rats have also had a good feed on the
insulation....

It is rather difficult for anyone to give a definitive answer to your
problem on this forum, without having heard the symptoms. We can only
go on similar symptoms experienced by some of us and make suggestions
as to possible causes.

Good luck....

 

[Ron]

Ron wrote:


(snip)

I can't help thinking that you may have a fault in the first or second
stages of the amp. What does the guitar actually sound like when
playing through it? Is it extremely distorted? or clean if only the hum
wasn't there? I have one of those little Fender Frontman 15w amps that
was very noisy but was due to one of the input stages shorted inside
the first dual op amp. It's relatively easy to blow the first stage of
preamplification by overdriving it with a guitar effects unit/pedals

Hi, Richard;

I didn't even have time to blow it, rather, the hum was there from the
first moment I plugged the guitar into the amplifier. The sound from
the guitar is clean except for the hum, but as I found out, the hum is
only present when the guitar cable is plugged in suggesting that the
[cheeap] cable is most likely to be at fault.

Ron

 

[ian field]

Ron wrote:


(snip)

I can't help thinking that you may have a fault in the first or second
stages of the amp. What does the guitar actually sound like when
playing through it? Is it extremely distorted? or clean if only the hum
wasn't there? I have one of those little Fender Frontman 15w amps that
was very noisy but was due to one of the input stages shorted inside
the first dual op amp. It's relatively easy to blow the first stage of
preamplification by overdriving it with a guitar effects unit/pedals

Hi, Richard;

I didn't even have time to blow it, rather, the hum was there from the
first moment I plugged the guitar into the amplifier. The sound from
the guitar is clean except for the hum, but as I found out, the hum is
only present when the guitar cable is plugged in suggesting that the
[cheeap] cable is most likely to be at fault.

Ron

Plug the cable into the amp and instead of plugging the other end into the
guitar - short the tip to the body & see if the hum stops.

 

[Ron]

(snip)

Plug the cable into the amp and instead of plugging the other end into the
guitar - short the tip to the body & see if the hum stops.

Hmm, actually that makes the hum worse.

Ron

 

[Pooh Bear]

Hmm, actually that makes the hum worse.

The amp's faulty in that case.

Graham

 

[Arfa Daily]

The amp's faulty in that case.

Graham

It's hard to see in what way the amp could actually be faulty, though, given
that Ron said that the guitar is perfectly clean and correctly amplified. If
the cable is poor quality, with a less than adequate shield, shorting inner
to shield at the remote end, could be just turning it into a long single
turn hum pickup loop, particularly if the environment is electrically noisy
or there are any power earth integrity issues.I would still feel inclined to
try another better quality cable, or take the whole shebang across town to
your sister's house, or wherever, and try it there.

One slight possibility comes to mind. Does the amp seem very very sensitive
? That is, does it sound like you've got sort of full chat, with the gain
control up at only say number 2 ? The reason I ask this, is that I did once
have a ProSound combo that suffered intermittently from hum, and it
eventually turned out to be due to a feedback resistor in the first opamp
stage, that ws going intermittently open circuit, increasing the gain of the
stage so much when it did, that it picked up huge amounts of hum.

Arfa

 

[Ron]

(snip)


One slight possibility comes to mind. Does the amp seem very very sensitive
? That is, does it sound like you've got sort of full chat, with the gain
control up at only say number 2 ? The reason I ask this, is that I did once
have a ProSound combo that suffered intermittently from hum, and it
eventually turned out to be due to a feedback resistor in the first opamp
stage, that ws going intermittently open circuit, increasing the gain of the
stage so much when it did, that it picked up huge amounts of hum.

Arfa

Hi, Arfa;

No, except for the hum when the cable is plugged in, the amplifier
behaves nicely and normally at all settings.

Ron

 

[Arfa Daily]

Hi, Arfa;

No, except for the hum when the cable is plugged in, the amplifier
behaves nicely and normally at all settings.

Ron

Then it's a cable or operating environment issue, not a fault. Like I said,
try relocating it to another house temporarily, and see how it behaves.

Arfa

 

[Ron]

Then it's a cable or operating environment issue, not a fault. Like I said,
try relocating it to another house temporarily, and see how it behaves.

Arfa

I went into my office, the only part of the house with all new wiring
and virtually no 60 Hz noise, and tried the guitar and amplifer. As
before, no hiss or hum untilt the guitar cable is plugged in. This
pretty much cinches it for the prblem being in the cable.

Ron

 

[Arfa Daily]

I went into my office, the only part of the house with all new wiring
and virtually no 60 Hz noise, and tried the guitar and amplifer. As
before, no hiss or hum untilt the guitar cable is plugged in. This
pretty much cinches it for the prblem being in the cable.

Ron

Agreed

Arfa

 

[Michael Ware]

On 16 Jun 2006 05:44:33 -0700, "Ron" <[email protected]> wrote:

It is rather difficult for anyone to give a definitive answer to your
problem on this forum, without having heard the symptoms. We can only
go on similar symptoms experienced by some of us and make suggestions
as to possible causes.

Good luck....

Yes, way too many variables. Especially for a guitar/cord/amp combo that
cost a total of $100.

Did you try...

1)same guitar/cable, different amp
2)same cable/amp, different guitar
3)same guitar/amp, different cable

I don't remember if you mentioned, where did you buy this set? Online, or
through a catalog? I would take all this stuff down to a good music store
( a MUSIC store i.e. musical instrument sales, not a record store). Any
reputable shop will be happy to help you isolate the problem, maybe even
offer suggestions to correect. Of course, depending on the salesman, the
correction could be rather pricey

 

[Ron]

Yes, way too many variables. Especially for a guitar/cord/amp combo that
cost a total of $100.

Did you try...

1)same guitar/cable, different amp
2)same cable/amp, different guitar
3)same guitar/amp, different cable

I got the combo from Amazon.com, and now I have only one guitar
(well... except for my old Casio DC-10 digital geetar, but that's a
horse of a different color) and *one* amplifier so I have to rely upon
the evidence at hand which points to a cable problem. I've ordered a
new shielded cable, and in about a week or so, I'll know for a fact
whether it's a cable problem or not. What was it Sherlock Holmes used
to say? Eliminate the impossible and no matter how improbable, what
remains has got to be the answer? Something like that... Anyway, going
to a music store is a last resort for me as I have way too many other
things to worry about these days. But nine will get you ten the problem
is in the current cable.

Ron

 

[Ron(UK)]

The amp's faulty in that case.

Graham

Or the screen is open on the cable.

Ron(UK)

 

[Ron(UK)]

Or the screen is open on the cable.

Ron(UK)

Or the ground side of the input socket is open circuit, probably
fractured solder joint. It will ground when no plug is inserted if it
has a shorting contact on both sides.

Ron(UK)

 

[Arfa Daily]

Or the ground side of the input socket is open circuit, probably fractured
solder joint. It will ground when no plug is inserted if it has a shorting
contact on both sides.

Ron(UK)

--
Lune Valley Audio
Public Address Systems
Hire Sales Maintenance
www.lunevalleyaudio.com

But he has said that it all works ok with the lead and guitar plugged in -
guitar sound is normal, amplification level is normal, just rather too much
hum. Thus, there cannot be an open circuit either on the cable shield, or on
the ground PCB terminal of the input jack ...

Arfa

 

[Michael Ware]

I got the combo from Amazon.com, and now I have only one guitar
(well... except for my old Casio DC-10 digital geetar, but that's a
horse of a different color) and *one* amplifier so I have to rely upon
the evidence at hand which points to a cable problem. I've ordered a
new shielded cable, and in about a week or so, I'll know for a fact
whether it's a cable problem or not. What was it Sherlock Holmes used
to say? Eliminate the impossible and no matter how improbable, what
remains has got to be the answer? Something like that... Anyway, going
to a music store is a last resort for me as I have way too many other
things to worry about these days. But nine will get you ten the problem
is in the current cable.

Ron

Yes, might be the cable.
What sort of pickups does the guitar have? Single coil? Humbuckers? Single
coil pickups can be very, umm, hummy.

 

[Arfa Daily]

Yes, might be the cable.
What sort of pickups does the guitar have? Single coil? Humbuckers? Single
coil pickups can be very, umm, hummy.

That is very true. Usually, if the problem is due to pickup in the pickup
( if you see what I mean !! ) it is substantially affected by touching the
strings or the surface of the pickup. A decent cable can make all the
difference with a single coil pickup.

Arfa

 

[Ron(UK)]

That is very true. Usually, if the problem is due to pickup in the pickup
( if you see what I mean !! ) it is substantially affected by touching the
strings or the surface of the pickup. A decent cable can make all the
difference with a single coil pickup.

Arfa

As it happens, I just had a Roland combo come in for repair with the
same problem, humming regardless of whatever was plugged in. It turned
out to be the shorting contacts on the second input socket (overdrive)
tarnished. Of course guitar boy always plugs into the first socket
leaving the overdrive socket open to the elements.


Ron (UK)