How quiet is your MkV???

Hi All!

Off standby with all masters at 0, do you get noticeable noise through
the speaker (hum etc)
We re tackling a 100hz hum-through speaker issue with my tech, it's been discussed
extensively in another thread so no reason to over it again and try
troubleshooting.
Just your impressions. What I am looking for is a 100hz hum ( low G#) as loud as the fan and present with masters at 0 at 90W and all modes, channels etc as soon as you go off standby to play.
Or any other type of noise, not necessarily 100hz hum.

Only asking 'cause so far I'm getting the "all loud high-gainers hum"
response which I don't remember being the case at least with my MkV before a power tube
issue that has now been sorted.
Amp does this in every location-building I've plugged in while troubleshooting for bad power.
the tech will check the guts for filtering and ground next week but has been hesitant to do so so far
as the amp otherwise works fine.
I would appreciate your input.

Thanks,
T

With all masters at zero the only noise i get is the fan. Totally clean. All channels.

Mine is very quiet except for its occasional radio transmission reception. :lol:

Have no noise what so ever. Even with the masters set to 9oclock and nothing plugged into the input or on the effects loop.
I do get similar noise only with the clean channel but is not very noticeable unless the masters are dialed up.

Mine was pretty noisy until I put in new tubes.

Then quiet as a mouse.

It got noisy again, and this time I realized just in time that it was a cable. This saved taking apart the blasted thing to get access to all the tubes.

Mine is quiet as well.

Mine has a quiet hum if you put your ears close to the cab, and when you completed turned down the master volume. My tech said it's from a power supply coupling with the preamp tube.

^^^
Glad I'm not alone.
I had the humming boogie replaced with a brand new one and there is a very slight hum in that one too.
quieter than the first one but still there. It doesn't bug me that much tho and from the techs that went through the first one I know it's not about to blow up on me.
Signal to noise ratio is indeed very good and I do need to put my ears near the cab to hear it with the new one.
problem is it's hard to give it a rest once your ears know what to look for.

This bugs me a little too but as you mentioned, the signal to noise ratio is so great that this doesn't even show up on a recording. So I can deal with that. On a side note, my mark IV is completely quiet with the volume all the way down for some reason.

I got a pretty loud hum, varies through channels. No changes if I remove V1 - V6 or if I change power tubes or remove the rectifier tube.
It only disapear when I remove V7 or the power tubes.

crane said:

I got a pretty loud hum, varies through channels. No changes if I remove V1 - V6 or if I change power tubes or remove the rectifier tube.
It only disapear when I remove V7 or the power tubes.

Click to expand...

Yeah, that's what I had although it didn't vary with channels. How loud is pretty loud? Unfortunately there is not global reference for these terms.
Apparently even "dead silent" has many different perceptions.

Anyhow, is it louder than the fan?

Hard to say, I'll try with "as loud as the fan" but in a totally different frequency. I'll take a record of it to point if it is a heater or rectifying problem.

Mine is as loud as the fan, with all volumes down, on Chan 1. If you are 6 feet away from the cab, you won't hear as much. My mark iv on the other hand is dead quiet. I have changed V1, yielding no different result.

6-7ft away and I won't hear it as well.
The hum doesn't change with the volume so it's not a problem when in a band, but i just want to find what the problem is.

I'm not sure about this but does this have anything to do with the DC heater for the tubes?

Low pitch hum like this at 100Hz roughly points to heater hum usually but, whatever it is I think it is inherent to the design.
I've stopped chasing it tbh

does this have anything to do with the DC heater for the tubes?

Click to expand...

Shouldn't.
I can remove V1 to V6 without changing that hum.

I think I located the source. Put your amp on standby. Put your ear on the amp head shell, close to the power transformer (turn your fan off). Now put your amp off standby, all of a sudden you hear the transformer adding a hum, which is the exact tone as you hear from the cab...

The transformer is vibrating ? if it's that it could be (usually) easy to fix !
Thanks, I'll check it tonight.

The transformer adding hum is more likely electrical rather than vibration, no?