How quiet is your MkV???

[crane]

Physical vibration can occcur, if the PT is undersized, or has a small shortcut in the secondary section (and acting like a heater in this case), and can be transmited to the audio chain.
If it's vibrating I'll try to screw it tighter or looser, or place some bumpers and see if it solve the problem.

 

[shredding]

Crane, I think it's from the transformer but when I put my hand on it, i couldn 't feel the vibration at all. But you do hear a clear audible vibration added the moment I take off standby. Are there any other components in the chassis that could be vibrating?

 

[shredding]

Called mesa and they told me this is completely normal.

 

[Catthan]

I think it is too.
Had 2 so far that did it with the new one being slightly quieter, don't know if that means the first one had something going on

 

[bandit2013]

I would agree with the transformer vibration. The filament transformer is made of stacked steel plates, a primary winding along with many secondary windings. You can hear the transformer making the noise but you will not feel it. Vibration is caused by the changing magnetic field. That is normal noise. You should hear the Roadster at start up, definitely the transformer. Capacitors can also vibrate, especially the ceramic multilayer type (phenomenon is termed piezoelectric effect). The noise may be audible but mostly will not wind up in the signal. Power supply ripple (current or voltage) is usually what is heard in the audio signal. Most of the ripple should be filtered out. Tube heater type: The Mark V uses two types of heater voltages. AC heater voltage is applied to V3, 4, 6, and 7. All of the power tubes use the AC voltage for the heater as well. V1, 2 and 5 are supplied with 12Vdc for the heater which is typically used in the more sensitive circuits. Another source of vibration and audible noise are the tubes them selves. Some preamp tubes (long plate design) as well as the power tubes and rectifier tube will create noise. This can be heard at low volume, sometimes the noise will be captured in the signal as well (usually caused by a preamp tube). Most of the low frequency hum is caused by the magnetics (transformer and choke) if the noise is in the 60Hz range. Power supply noise in the signal is generally in the 120Hz range since it is a full wave bridge design. There is one supply circuit that is half wave rectified which is the bias voltage circuit which may contribute to the 60Hz noise.

 

[Catthan]

@bandit2013 I understand you know a lot about how these things work.
Out of curiosity, what would you think a 100hz hum is?
In the UK so that's double the grid frequency. I've read it's usually associated with the heater but being in the UK, is it most likely from the grid?

 

[guitardr]

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

Same here: w/o the fan it's noiseless (virtually).

 

[tele_jas]

My Mark V is pretty quite... Even with the master up about 1/3 the way, the noisiest channel is channel 1 in Tweed mode, I get a slight hiss. But Channel 2 in Mark 1 mode and gain about 2:00 and channel 3 in Mark IV mode with the gain maxed and treble about 2:00 are both quieter than channel 1. When I switch modes on channel one (to clean or Fat), the hiss goes away so it's just that mode and it's not bad at all, but still more noisy than the two dirt channels.

I would like to say that there is one room in my house that makes EVERY amp hum at about that 100hz. I noticed it a few years ago (about 2007) with a boutique amp I had and sent it back to be repaired, I thought it was the transformer. When the builder got the amp, he couldn't hear any hum and sent it back. When I plugged it in, even with the volume at 0 it still hummed. I then tried my other amp, which I should have done to start with, and it hummed the exact same way! Every amp I'm had since then also hums in that one room in my house (my bed room, of course). When I take it to a different room or to a gig, there's no hum. Must be something funky with my wiring in that room?.... I even replaced the receptacle in that room, and it still hums.