Mark V - Hum Question

[iggs]

Hey all,

Just got a brand new out of the box Mark V combo. Love the amp, sounds amazing.

Just checking on one thing ... there is a low level hum when amp is off standby.
It is not affected by either gain, EQ or volume settings. It goes away in Mute as well.
It slightly varies in level between 90, 45 and 10W modes.

I have switched the rectifier with a new one but nothing changes.
One of the inner pair tubes had a burn mark on the inside of the plate, I thought it might be bad so I got a replacement set and the hum persists.

Anyone have an idea of what that might be or is that just normal for Mark V?

Here's a short video demo: https://youtu.be/GBi4tPEKQfs

Thanks!

 

[Monstercastle]

Doesn't seem that bad to me. Looks like you are on Extreme mode, with the gain around 3:00 and the treble up. Does it do this in all channels and modes or just 3/extreme?

 

[iggs]

Doesn't seem that bad to me. Looks like you are on Extreme mode, with the gain around 3:00 and the treble up. Does it do this in all channels and modes or just 3/extreme?

All channels/modes and is not dependant on gain or level settings ... it does not get quieter nor louder as I turn it up/down.

 

[jb's 52]

Hmmmm...

It doesn't sound that bad in the video, but a hum is usually a power tube IME. Did you swap both pairs or just the inner pair?

 

[iggs]

Hmmmm...

It doesn't sound that bad in the video, but a hum is usually a power tube IME. Did you swap both pairs or just the inner pair?

Just the inner pair as one was looking suspect with a burn mark ... was hoping that would solve it.

 

[jb's 52]

Yeah...try the outer ones next.

 

[iggs]

Yeah...try the outer ones next.

Just did yesterday and it's pretty much the same ... guess I'll have to live with it.

 

[jb's 52]

Do you notice the hum in other locations as well?
The reason I ask is that it may be related to one specific power circuit.

 

[iggs]

Do you notice the hum in other locations as well?
The reason I ask is that it may be related to one specific power circuit.

Haven't tried yet to be honest, you're right tho, it may be something to do with the power in my place.

 

[Catthan]

Judging by the 2 MkVs I've had it will hum a bit at 90W.
Mine hums more when I have fx running in the loop.

45W ain't so bad and it should be quiet enough for home playing.
Live you won't notice it.

The only thing i Found that affected the hum, not by much tho, was swapping v1 pre- tubes.