Good scare and need advise - Mark V:35

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jlapalme

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Hi,

I got a good scare today.
I miss read a piece of equipment (Tow Notes Torpedo Live - a load box with a speaker through out jack) and didn't realize that connecting a wire to the through output jack disconnected the loadbox portion of the unit. In many circumstances, this is not a problem. In my case, the other end of the through out cable wasn't connected to a speaker Cab. Hence, to my understanding, the amp was without a proper load.

More specifically, I had connected my tube amp head (Mark V:35 in 35watt mode) to the input jack of the Torpedo Live unit. I had also connected the through out jack of the unit to my speaker CAB. During my recording session, I need to cut the sound from my speaker CAB so I disconnected the cable from behind the speaker Cab. I noticed a change in the sound but keep playing a bit. After about a minute or two, I tried disconnecting/connecting the cable from the Live unit though output jack and noticed tone/volume changes (better without the cable).

From my understanding, when the cable was connected to the through output jack (but not in my speaker CAB), my amp head was without a proper load.

What I don't understand is why :

1. My amp fuse didn't blow (or the power section) ?
2. Why signal was still being sent from the Torpedo Live to my audio interface and DAW ?

Now, wanting to check the state of my amp, I did some quick tests and discovered something and would like to know if it indicates possible damage :

With all the knob set to zero (gain, treble, mid, bass, presence and master), I basically hear no noise (besides the fan). Now, as I increase the presence (while keeping the other controls at zero), I hear an increasing louder hum. The two channels in all the modes do the same thing. Now to put things in perspective, if I play my guitar, the hum is buried by my playing. I get a similar behaviour with my Mesa Boogie Roadster but I don't get it with my Message Boogie Lonestar LS.

So to recap, here are my questions :

1. Why didn't my fuse or power section blow ?
2. Why did I still have a signal going to the DAW ?
3. Is it normal that with all knobs at zero my amp is quiet but if I only increase the presence I get a hum ?
4. If the hum is normal, why ? If it is not, is it related to my miss-up or is it a coincidence that I just realize that I had a problem (I don't spend my time listening for hums in my gear with different settings of my controls) ? The underlying concern that I have is that I'm getting a 60hz hum because of a failed tube or worse a 120hz hum caused by a failed filter cap.

Please reassure me!

Cheers,

James
 
Other than opening her up and seeing if anything looks or smells burnt unless your up to speed with the technical side of valve amps I'd say get a tech to check over it. Better to find a component that's about to fail and replace it before it does fail and cause more damage. Chances are that everything's fine though.
 
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