DSL40C hum

[Havoc]

My DSL40C seems to have developed a pretty loud hum. Who are the usual suspects?

 

[Micky]

Guitar.

Is anything plugged in?

 

[Havoc]

ive run the guitar straight in and through pedals, no change.

 

[Micky]

But when you unplug everything the hum goes away?

 

[Havoc]

Have not tried that yet. If the hum doesn't go away, what are your thoughts?

 

[TheSunShinesThrough]

Try new cables, new guitars. Check jacks make sure they're plugged in right.

 

[bigbadorange]

Try a bigger font on the lyric sheet.

 

[John 14:6]

My DSL40C seems to have developed a pretty loud hum. Who are the usual suspects?

A microphonic preamp tube. Is this the noise?

[ame="http://www.youtube.com/watch?v=QM2qWZYbInI"]www.youtube.com/watch?v=QM2qWZYbInI[/ame]

 

[Havoc]

I only get to play the amp once a week being that it sits at practice rather than me lugging around. So I haven't played it since last week.
We played this weekend and the hum seemed better. Mid way through the set it just stopped working. I'm hoping it's just a bad tube.

 

[Micky]

So did you unplug everything from the amp? Did the hum go away?

Put in your spare set of tubes to see if it makes a difference...

 

[John 14:6]

I only get to play the amp once a week being that it sits at practice rather than me lugging around. So I haven't played it since last week.
We played this weekend and the hum seemed better. Mid way through the set it just stopped working. I'm hoping it's just a bad tube.

When tubes go bad they can do so intermittently. It is common to have on and off again problems. Periodic volume drops are common along with periodic noise, hum and tone changes depending on the tube problem.

 

[Havoc]

Got the amp back today. Tech said there was a design flaw with the way the input jack connects to the circuit board.

 

[Havoc]

So the amp shut off on me and I got it fixed, hardwired the input jack to the circuit board, but it still has this loud hum. Only when things are plugged in and mostly on the red channel. Unplug everything and it goes away.

 

[Micky]

So the amp shut off on me and I got it fixed, hardwired the input jack to the circuit board, but it still has this loud hum. Only when things are plugged in and mostly on the red channel. Unplug everything and it goes away.

Then it is not the amp...

 

[MarshallDog]

Very interesting, I have not heard of any design flaws. Did he change out any preamp tubes. I had this happen to my Jubilee a few weeks ago and it would hum only on channel 2 (the high gain channel) but on channel one it was fine. Changed out the V1 tube and all is fine.

 

[Havoc]

The tech said the design used a plug in from the input jack to the board so he just hard wired it.
I will look into the tube swap.

 

[John 14:6]

My DSL40C seems to have developed a pretty loud hum. Who are the usual suspects?

Bad preamp or power tube.

 

[ken361]

I had a preamp tube cause a hum, too bad I liked the tube try switching them around.

 

[Micky]

But if you unplug everything, and the hum goes away, how can that be the amp?

I would be looking at the guitar, the cables, and any FX you might be using first...

Have you tried a different guitar? Different cable?

 

[Jethro Rocker]

If it's quiet with no input the issue is not amp!! Micfophonic tubes sing songs on their own with no guitar. Poor guitar shielding, poor cable, mostly red channel could be an excessive gain setting with amp turned up and a poor guitar shield. There will always be a bit of hum in that case.