Vacuum tube (Valve) Amplifier Hum - opinions please

[Tapster]

I have just bought a new electric guitar amp.

 

It is powered by vacuum tubes (valves).

 

The amp has a lot of hum when a guitar is plugged into it. This detracts significantly from the sound and is very annoying for all concerned.

 

The hum is not the fault of the amp itself, rather it is caused by something in the mysterious Thai house wiring, probably the lack of an earth/ground on the plug.

 

Also, I don't want to risk electrocution if the amp malfunctions and high voltage comes to the chassis of the amp. I already get little shocks all over the house, fromPC and audio equipment.

 

Can anyone help with this, please?

 

Many thanks!!     

[Crossy]

Almost certainly lack of a ground on your amp, a suggestion backed up by your getting tingles from other kit.

 

You need to provide a ground, are you in a house or condo?

 

House is easy enough, go and get a rod, bash it in and connect it to the ground pin of your amp. That should sort your hum for now but you really need to do the job properly for your other appliances. Are you renting or owning?

 

[Tapster]

Thanks Crossy,  I suspected the ground of the house circuit.

 

We fitted an RCD 18 months ago, on the fusebox/consumer board. It only works in the dry season. As soon as there's any wet, it trips and won't reset. I'm not entirely sure what that means but it's not a good thing.

 

We own the house - single storey with adjoining workshop/office.

 

What do you recommend? I don't want to go on like this. The amp will continue to make noise and presumably we migth get a serious shock from something at some point.

 

Cheers

[Crossy]

OK, you have several issues:-

• No ground anywhere in the house
• An RCD that trips in wet weather

Firstly I would get a rod (a 1m one will do for now) and ground your amp, that will sort the hum.

 

Then determine which of your appliances are Class-1 (need a safety ground), these are usually white goods and desktop computers.

 

Then you can decide the way forwards, ground the whole house (if it's yours that's the best way to go) or just provide grounds where they're needed (for those renting).

 

For your tripping RCD, do you have any outside lights or outlets? Pop them off the wall (power off) and clean out the ants etc which have taken up residence, drop a couple of naphthalene balls in the back box to discourage them from coming back.  Any boxes that are damp, leave them open and let everything dry out. Leave the power off, or if you need power on ensure small fingers cannot access any open boxes.

 

Is the wiring to your outlets in conduit (tubes) which you could get an extra wire into? Failing that you could drill through the wall and run a ground cable round the outside.

 

[bankruatsteve]

I suspect you don't have "house ground" and will need to take action as Crossy explained.  The RCD tripping is most likely from a dirty/insect-filled/gecko outlet box or even switch box getting damp resulting in a small fault but enough to trip.  You can try checking/cleaning the boxes to eliminate the trip but need ground for your amp.

 

Oops, I thought you had left the office Crossy.  Delete this if you want.

[Tapster]

 

OK, cool, thanks.

 

Good advice. I didn't know about the outdoor plugs and lights - we have quite a few.

 

A couple of queries:

 

 - You actually mean run a wire from the  earth of my amp, out of the house to a conducting stake driven into the ground?
That doesn't make the amp very portable, but that's not a problem for now....and it might need this grounding when I go to other venues which may not have a good ground.

 

 - All the plugs that I have put on our electrical goods are two-pin, because that's what most things in Thailand seem to have. If I get the house grounded, I presume I'll need to replace the plugs with three pin, with ground wires.

[Crossy]

Yes, you need to provide a ground to your amp, there's no way round it, if venues don't have grounded outlets ensure you have a short rod and a long length of wire to provide a ground.

 

If you kit has 3-core flex it needs a ground to be safe, fit 3-pin plugs and outlets and run ground wires to the outlets.

[RichCor]

Here's a YouTube video explaining guitar hum issues...

 

 

[Tapster]

Thank you, gentlemen!

Most helpful. 

I'll improve the house system, but first run a ground cable from the amp. 

 

[RichCor]

Yea, if the amp or guitar are giving you a tingle then that's not a good thing. Either there's a voltage leak occurring in the amp or your household Neutral has a higher potential than Earth and when you touch metal you become an unwilling Earth-Neutral-Bond substitute. 

 

Most likely your household neutral is not at the same potential as earth-ground. 

 

As Crossy mentioned, your consumer breaker box should have a functional Ground connected to a copper rod bashed into wet-ish earth. Should also check that the Neutral and Earth Ground are 'bonded' (have a connecting wire) in the consumer breaker box so Earth-Ground and Neutral are tied together and have the same voltage potential. 

 

[Tapster]

OK, experiment completed!!!

 

I have a one metre steel stake, hammered into the ground outside my workshop, connected to the ground wire of my amp....................and there's no noise!!!

 

I soldered the ground wire of my amp to the aforementioned stake.

Therefore , it must be the house wiring and its lack of a satisfactory ground....yes???

 

[Crossy]

Yes

 

[Tapster]

On a purely practical note, does adding a third wire (ground) to every socket in the house mean completely rewiring the house?

 

It doesn't sound like an easy job to leave the existing wiring and add an earth wire running in all the conduits.

[bankruatsteve]

Yes and No.  You already have L and N run so it's a matter of adding the ground.  If the wires already in conduit, you probably will have to pull out the existing wires (attaching a sturdy string to the extremity), connect the ground to the string attachment, and then pull back the original bundle plus ground.  That may/may not be a simple thing to do.  It's unlikely that you can just run the ground through conduit with wires already in it because it always gets stuck about 2 meters in.  (in my experience trying to do that)

 

 

 

 

 

[Tapster]

Thank you, Steve.

 

That makes sense!

 

[jpinx]

4 minutes ago, Tapster said:

Thank you, Steve.

 

That makes sense!

 

 

A couple of little tips on the side ....

 

When you run the ground wire through your conduits, make sure you also run a blind line through as well -- for the next time you need to pull another wire through.  Heavy fishing line is a good blind line.

 

Make sure the line from the Amp to the Guitar has the outer braiding properly soldered to the earthing connections at both ends, and make sure your guitar has all the backing plates of the pickups, etc all well-connected to earth.   Safety as well as sound quality is improved a lot by a good earthing system.

 

The earthing rod for the house should be a length of heavy-walled copper pipe driven at least a metre into some nice loam soil, preferably somewhere where the ground stays a bit moist.  Using copper increases the conductivity and encourages the stray voltages away, and using pipe means you effectively double the surface area of contact between the earth-rod and the soil.

 

 

[bankruatsteve]

17 minutes ago, Tapster said:

Thank you, Steve.

 

That makes sense!

 

 

Just to add... If you have a single 2-core cable in conduit, then you might be able to run a 1.5mm2 ground without problem (without pulling the other cable out).  Try that first and maybe lucky.

[Tapster]

Excellent advice, thanks!

 

[Tapster]

 

Some more advice, please.

 

Please read all of this if you have time....it's not too tedious.

 

 

I have checked, and my mains sockets around the house and all have three wires!!!

 

 

So, there is an earth wire!

 

I'm assuming that:

 

 - All two-pin appliances do not make use of the earth wire and do not need it??
 

 - I must change the plugs on all my three-wire appliances to three-pin plugs, to make use of the earth.

 

 - I must change all my two-pin extension power strips to three-wire (earthed) strips....................and where can you buy these?? All Thai power strips seem to have only two wires and contacts.

 

 

I've just tried to use my new amp (now earthed and without hum) with an effects pedal (9V DC) run off a two-pin voltage adapter plug. The hum is back, but................

The adapter (mini transformer) has no earth wire, so how can I earth it to stop hum??

 

Madness ensuing and pulling hair out!!!

 

[RichCor]

2 hours ago, Tapster said:

[...]

I've just tried to use my new amp (now earthed and without hum) with an effects pedal (9V DC) run off a two-pin voltage adapter plug. The hum is back, but................

The adapter (mini transformer) has no earth wire, so how can I earth it to stop hum??

 

Madness ensuing and pulling hair out!!!

 

 

Generally, what you are describing with your AC adapter is called ground-loop interference.  The Video I posted previously went into this at around 5:50.  But I would be really interested in how you answer this next question.

 

I believe you wrote that you fitted an RCD on your Main Breaker / Consume Board.

 

Where it the Earth Ground - Neutral  bonding happening:

o   Before the RCD (upstream, as is should)

o   After the RDC (before the breakers so it can cause the RCD to false trip)
o   Not bond at all (allowing Neutral and Ground base values to vary widely from each other)

 

[jpinx]

Did you trace the "earth wire" of the house circuit to the ground stake?  Lots of times this is missing

[RichCor]

4 minutes ago, jpinx said:

Did you trace the "earth wire" of the house circuit to the ground stake?  Lots of times this is missing

 

...or the connection or stake eaten away due to corrosion.

[Tapster]

18 minutes ago, jpinx said:

Did you trace the "earth wire" of the house circuit to the ground stake?  Lots of times this is missing

 

No.

 

Where would I find this earth wire and the stake?

 

What exactly might it look like and would it be close to the fuse box, or elsewhere?

 

22 minutes ago, RichCor said:

 

Where it the Earth Ground - Neutral  bonding happening:

o   Before the RCD (upstream, as is should)

o   After the RDC (before the breakers so it can cause the RCD to false trip)
o   Not bond at all (allowing Neutral and Ground base values to vary widely from each other)

 

 

 

Er, what is Ground-Neutral bonding?

 

[jpinx]

Sounds like you need a professional electrician

[bankruatsteve]

Do you have the ground wire to all your sockets showing up in the CU?  And is there then a connection from the CU ground bar to a ground rod?  You do not have to replace 2-pin plugs for 3-pin unless the equipment is "Class-1".  If you don't know then try to find out.  

 

RichCor:  The RCD will work as it should no matter where the ground is placed or whether there is ground or not.  If it is bound to the neutral then it should be a "MEN" setup which may not be the requirement for the OP.

[RichCor]

On 12/21/2016 at 8:31 PM, bankruatsteve said:

RichCor:  The RCD will work as it should no matter where the ground is placed or whether there is ground or not.  If it is bound to the neutral then it should be a "MEN" setup which may not be the requirement for the OP.

 

I'm assuming a 'MEN' setup, but wondering if some of the 'noise' issues are due to missing or incorrectly placed G-N bound. If Neutral is allowed to 'float' (as opposed to being tied to and referenced to a working ground) then this can cause all manner or EMI/Noise inductance issues on mics, pickups and unbalanced signal cables.

 

TAPSTER:  What happens if you take your rig to other locations and plug it in -- do you have the same/similar noise issue?

 

Many musicians I know will either employ an isolating transformer to plug all their equipment into or run as much as they can off batteries,  just to get the isolation.

 

Another 'option' would be create your own portable 'utility' power junction box, containing all the outlets you may need for amps and sound equipment, then have a dedicated grounding cable that you can run and attach to a short copper spike you stick in the ground.  Your junction box would eliminate ground loop noise as all the equipment would run off the same commons.  The issue that you couldn't mitigate with this would be if the feed electrical contained a borrowed neutrals or floating neutrals causing neutral values to deviate from ground, inducing noise in your sound system.

[Tapster]

Mmmm...........

 

OK, you are now talking Greek to me.

 

I don't understand that level of electric tech.

 

It would be great of I could get a sparky that I can trust to do the job right..............but I'm not sure I can. That's the whole point of my posting here.

 

• Firstly, I want to get the ground in my house sorted out, so that the devices attached to it will not hum.
   
• The ground-loop is a red herring, I think, because it's an effect that happens when different devices are connected to each other in a loop, which causes hum. My hum is caused directly from connecting to an un-grounded mains supply.

What I'd like to know is how to test  whether all my 3-wire plugs are really providing a ground, because I don't think they are.

 

[RichCor]

On how to test the 3-wire sockets...   there are simple testers you can purchase for relatively cheap that can test if all wires are active. Though you need one specific to THAILAND to get the proper results (Live and Neutral  indicators may be reversed on imported testers).  

 

Do you know any expat locals who may have had electrical work done and can recommend someone?

 

I would think Phuket would have many electrical supply shops. Do any have owners/employees that speak English, or do you have a close knowledgeable bilingual Thai friend that can spend time and interpret while you got your home system evaluated for issues? 

 

It's hard for us to go into more detail if you've never had prior experience checking/wiring home electrics.  Some simple 'testing' usually requires the person have a bit of experience and the knowledge of safe practices so they don't wind up dead.  

 

 

[bankruatsteve]

^agree with that.  If you just want to know if ground at the outlet is connected to a ground stake there is a simple test for that:  (you do have a ground stake now, right?)

 

Connect say a 2.5mm2 wire to your ground stake and long enough to reach the outlets you want to test.  Turn off power 'cause you don't need anything live to test.  Set your DMM to the ohms position and take a reading from ground in the outlet to the wire connected to the ground stake.  If it just sits at 0 and doesn't blink, then you have no continuity to ground.  If it blinks (like with a minus sign) or beeps or has a low reading (like <10 ohms), then you are good.

[Wirejerker]

On 24/12/2016 at 7:45 PM, bankruatsteve said:

et your DMM to the ohms position and take a reading from ground in the outlet to the wire connected to the ground stake.  If it just sits at 0 and doesn't blink, then you have no continuity to ground.  If it blinks (like with a minus sign) or beeps or has a low reading (like <10 ohms), then you are good.

Please don't follow this info as it is corrupt. The forum has told you what the problem is now get a electrician to fix it.