Sudden hum in VOX AC4TV full tube amp

[Jiriho]

I recently bought a brand new VOX AC4TV full tube amplifier 3 days ago. Since then the amp has been working great, however, today I hooked up a Joyo overdrive pedal to it, when I unplugged the pedal and I plugged in the guitar directly to the amp, there is a loud and constant humming sound coming from the amp, which becomes almost unbearable if I turn the volume knob past 12 o'clock. This happens with or without any pedals connected. I also haven't changed the location of the amp to where it was previously, and there is nothing around it that would cause interference. Also, when I unplug the guitar the hum continues with some crackling.

Now I'm wondering if the particular pedal that I plugged in has damaged the amp in some way, though I don't see how this could have happened. Does anyone know what might be wrong.

Appreciate any comments or help!

[alexradium]

If it hums without input plug, it's probably the ground connection cracked,I would reflow those jack pins

[pdf64]

For each tube socket in turn, I suggest to swap in your 'known good', spare tube of the correct type.

[Chuck H]

I don't expect anything about your pedal would have damaged your amp. A few thoughts...

Since you were using a pedal you had extra cords in use. Make sure the cord you are using is a shielded instrument cable and not a speaker cable.

Since you report crackling as well I'm actually suspecting a fractured ground contact due to input jack stress. this could be compromising other grounds in the amp too depending on how the circuit is arranged.

It may only be a bad ground on the instrument cable too that just happened to fail at that moment. Try another cable.

[nevetslab]

......and all this on a brand new amp???!!! As much as all of us want to pop the hood and go digging, no doubt finding the poor workmanship that unleashed this added audible bonus to a new customer.....I presume this amp IS under Warranty. Then, there is the trust factor.....do I take it back and insist on it being put back into proper condition at no cost, apart from the driving expense and aggravation? Or do what we normally do.....solve it, making sure not to leave evidence of the rework so the Warranty remains intact.

I agree with the speculations....fractured ground connections on the jack, as well as a tube having gone out to pasture.

Oh......and Welcome to the Forum!