Hum and Dad

[strummer10]

My wife and I recently had our first child. Why are you telling us this you ask? Well, I was playing the other day and my daughter started screaming so I asked my wife to turn off my amp whilst I attended to her. When I returned I realised that she had turned off my valve amp (Fender Hot Rod Deluxe III) at the mains socket (rather than turn it to standby and then turn the amp off). I've noticed since that when I turn the amp on, there's like an echo for a few seconds (a bit like a delay pedal) but the main difference is that when I engage my Boss OS2 (overdrive/distortion) there is a really loud hum. If I use my Strat it is worse in the neck, middle and bridge position which is something that I knew happens with single coils, but it was never really noticeable before. Could this be as a result of my wife turning the amp off at the mains? Or does it sound like the pedal has a problem? I'm a real novice when it comes to electronics so please bear that in mind with any suggestions you may have!

[AndyR]

The stand-by stuff is more for warming up your amp/valves, and keeping them warm, before thrashing away - so it's more important as part of the "turning it on" process.

Turning it off at the wall should be no problem at all - as long as you remember to turn the amp off (or into stand-by) BEFORE turning it back on at the wall.

For example, I remember years ago, working at a gig where the power was pulled (by a drunken idiot)... everyone dived for their amps and set them to stand-by, except the lead-guitarist. When the power was switched back on, everyone's amp was fine except for his - the surge blew the output transformer... But even that was unlucky, another time it wouldn't have happened.

So, I doubt very much turning it off at the mains would ever cause a problem. Turning the mains ON while an appliance is in the "on" position (or not on "standby" in the case of your amp) is more likely to be the culprit if there is any damage.

What I suspect is - are you worried that there might be damage, and so are hearing things you never noticed before?

BUT! I can't hear the sounds you're hearing, so maybe get someone else to listen to them so they can go "oh that's normal" or not.

I do have two things you can "test" with the hum:

Does the hum vary when you move the guitar around (change the direction it's pointing in, move closer/further to electrical stuff)?

And does it seriously reduce when you touch the bridge or strings (or the jack socket)?

If the answer to both is a firm yes, then it's probably normal - an OD is an amplifier, it amplifies noise as well as notes. Magnetic pickups are receivers of radio waves. Electrical stuff (including the wiring in your house) gives off radio-waves, this is the noise that comes out as hum. Single coil pickups are effected by it more. Humbuckers are designed to reduce this effect (and it sounds like you've got a Reverse-Wound/Reverse-Polarity middle pickup on your strat, this uses the same theory to reduce the hum in the Neck/Middle and Bridge/Middle positions). Oh, and electric guitars are designed to use you as part of the shielding (you interract with the radio-waves stuff as well), but this only works if you're connected to the guitar's ground circuit, via the metal work on the guitar.

But if the hum is constant while doing these two tests, then you might have something not quite right somewhere. Unlikely to be the amp, though (quick test - turn the OD off, is the hum still bad? If no, the amp is ok).


On the echo - dunno! I assume you mean this happens when you take the amp out of standby (not when you turn the amp's power switch on)? Has the amp got a reverb? Is it on when you "switch on"? It could be that.

[Hook]

Blame the kid and go shopping!

[Hilary]

Get the wife to look after the baby while you play the guitar - simples.

[Flash Harry]

Get the wife to look after the baby while you play the guitar - simples.

Hilary - that's shocking!

It could be a faulty lead, or it could be an earth/ground loop.
Faulty leads are easy to diagnose - just change the leads and see if the problem goes away - change one at a time and you can identify any that are faulty. A bad earth can cause hum.

Earth or Ground loops are a bit trickier to find. These occur when you have a number of individually earthed bits of kit in your signal chain. The earth wire forms a sort of antenna which injects hum into the signal chain. Some amps have an earth lift switch which will help to alleviate the problem, but some don't and just removing the earth wire from the plug is a BAD IDEA. Better to get good quality audio grade power supplies for your out board equipment such as O/D pedals and the like or run them on batteries.

I hope you get it sorted.

[Oldrottenhead]

not got a clue about the amp. but congratulations on the wee one. i'm sure she will inspire you write some songs.

[strummer10]

Thanks for all the replies. You might have a point AndyR - that I was expecting something to have gone wrong and am looking for it - but I genuinely cannot remember the echo before when turning the amp on and certainly the OS2 was never that noisy. I'll try it with my Les Paul and see what effect the humbuckers have on the, er, hum. I'll also try changing leads, but can they just 'go' - they tend to have a permanent home connected to the pedals and amp. The more I think about it I wonder whether in my 'disappointment' that my wife had turned the amp off at the mains (although to be fair, 99% of people would have done the same) I didn't think about putting the amp into standby again before turning it on. If that is what happened, and using Andy's example, would a new tube rectify the situation or is it much worse than that? And how much are new tubes? I've had the amp for 18 months from new so am not sure on the lifespan of valves. As ever, thanks for the suggestions.

[Flash Harry]

If you are going to 'blow' things - it tends to be the heaters on the valves, but it depends on how old your amp is.

Some old amps have dodgy capacitors in them that can fail when you just power up the amp without putting it in standby - this is because valves take a while to heat up and start to work, they don't work at all initially and this can cause high voltage spikes to wipe out the capacitors. New amps are less suceptibleto this.

If the amp is working, it's unlikely to be a valve.
If it's a real problem, take it for a check-up.

[strummer10]

The amp seems to be working fine apart from the echo when I turn it on from standby and loud hum when I engage the OS2 pedal. Even going from drive to more drive on the amp is fine and doesn't create a hum, which makes me think it could be the pedal. As for the echo, I do have a delay pedal (flashback x4) and reverb pedal (cathedral) in my chain (and also a little bit of reverb on the amp) so I'll try turning those off and see if that makes any difference when I turn the amp on (I'm not at home at the moment).

[chip]

Sounds like it may be a valve. My Roost developed a hum, but, it blew the fuse first then we discovered the blown valve. The pedals could also be the culprit too, there are many variables at work for me to give a definite answer . I have had some valve amps that hum all the time, the newest, The Vox AC4 hums quite loudly.

Valves can last for many years or a few minutes. A lot depends on how far you push them, for how long and how long they have been there. On average I changed mine when gigging once a year, but, the tiny terror could go through valves very quickly when driven hard for extended periods. The typical class A amp will burn them up much faster than an AB amp. However and I'm sure you know this, these things can be lethal in the wrong hands as far as self diagnosis is concerned, I always took mine to someone who knew about valve amps.