THR10C very loud hum/squeal

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Suncloud
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THR10C very loud hum/squeal

Unread post by Suncloud » Sat Apr 13, 2019 11:55 am

Hi guys,

not played guitar in a while because I was moving internationally. I bought a THR10C second hand a while before moving. Just dug it out again and remembered why I hated it: a loud hum and squealing sound when the guitar is plugged in and the amp is running on electricity.

Things I tried:
a) different amps have different levels of squeals/hums. The higher the amp number the louder. It doesn't stop when I play. Overall the sound is too loud to enjoy playing
b) tried different sockets, and even different countries now, with or without extension multi socket: no change
c) tried running on batteries: no annoying sound at all on either.
d) so I thought it's a broken charger. Ordered a new amp for testing.
d1) used old power brick and cable on all sockets on both units. Noise at exactly the same level on same model across both units.
d2) used only new power brick on both units: both the same
d3) used new cable on old brick on both units: same
d4) used new cable and brick on both units: again the same.

As the noise is not present when I run either amp on batteries, would that rule out a problem with my guitar cable?

Any other suggestions? I can't run it on batteries as it's against my ethics to use 8 new batteries every 2-3 days. Yamaha only suggest to go to a certified repair shop, but as also a new unit has exactly the same problem I wonder where the problem lies. Btw, in my old home I bought it to a guitar shop and I can't remember hearing the hum there. But that might have been due to more traffic noise in front of the door and inside the store. Can't remember if I brought my cable. I didn't have my guitar with me. Is that another option for the noise? It's a 52 reissue tele, and the shop used a similar one.
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Re: THR10C very loud hum/squeal

Unread post by Saul » Sat Apr 13, 2019 12:58 pm

Hi Suncloud, welcome to the forum :)

It's all a process of elimination and you have certainly done enough to narrow things down so. Both units work fine on batteries and with the same guitar lead? However both units exhibit the same noise when running on mains power. So that sounds like mains hum to me.

You took it to a store and there was no noise when plugged in there or not that you can remember. Trust your memory on this because I am guessing it is something you would have been concentrating on hearing so my guess is it wasn't there.

So that narrows things down to the power socket/supply in your home.

First thing I would do is get myself a good quality guitar lead and see if that helps. Leads are not all made equal and some are prone to more noise than others. It's a relatively cheap option and worth doing. By the way, have you tested the amp with other guitars? Possible it is your guitar that is the source of the hum/noise.

Other things to try are apower surge protector or ups. Plug the amp into that. You may well find the problem disappears.

If nothing else you are then eliminating the mains power supply as a possible cause and also you have a useful bit of kit to plug things into anyway so, that's a win :)

Most amps will produce some sort of noise at high volume but I have a feeling this is not the "normal" sort of noise one would expect from a guitar amp?
Saul
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Re: THR10C very loud hum/squeal

Unread post by Suncloud » Sat Apr 13, 2019 1:35 pm

Thanks a lot. I now went to a local guitar store and bought a new, fairly expensive guitar cable. Same noise. So that possibility is eliminated. The shop offered to test the amp for me as well if this doesn't solve the problem. The sales guy figured it might be an earthing problem.

I first bought this amp in the UK where sockets are build a bit differently, now I'm in continental Europe. I chose this amp because I can run it at low volume and it's small. Flat dwellers problems ;) I'd say the noise on the fifth model is as loud as the guitar when the master is on the lowest possible volume with good sound, and then gets louder as I turn up the volume.

So, earth cable thingy: All my sockets have the metal pins for that, but I can try those in the kitchen. Won't make a difference I think as I have an open livingroom/kitchen and all sockets look the same. I still use the UK plug, but also the euro one from the unit I ordered didn't make a difference in my livingroom.

It could still be my guitar but I don't have a second one and don't know anyone with guitar. I guess the problem is somewhere to be found in the mains supply/electricity cable as well. If it was my guitar it would be strange if it only produced this hum when on mains. Unless it's indeed a problem with how the electricity is supplied to the guitar via the amp.
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Re: THR10C very loud hum/squeal

Unread post by Suncloud » Sat Apr 13, 2019 2:14 pm

Ok, it's indeed the sockets!

I don't know what's different. I've tried all sockets with and without extensions in my livingroom and no luck. I tried the old cable and brick in the kitchen and it works as it should. A tiny bit of hum, but nothing dramatic. Right. How do I solve this problem then? Having the amp stand on my hob and play standing in the kitchen is probably not a good idea
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Re: THR10C very loud hum/squeal

Unread post by 314159 » Sat Apr 13, 2019 4:14 pm

Suncloud wrote:
Sat Apr 13, 2019 2:14 pm
Ok, it's indeed the sockets!

I don't know what's different. I've tried all sockets with and without extensions in my living room and no luck. I tried the old cable and brick in the kitchen and it works as it should. A tiny bit of hum, but nothing dramatic. Right. How do I solve this problem then? Having the amp stand on my hob and play standing in the kitchen is probably not a good idea
Hi Suncloud,

I suggest that you test the earth of all the sockets in your house. Some months ago I discovered that some sockets in my house had a bad earth: I was working on my freezer, and had a hand on the ground of the cellar and felt some electricity passing through me. Happily, the voltage was not too high :roll: . The earth of the socket of the cellar was (badly) connected to a socket in my living room.

If you have a multimeter (with an ohm-meter function) and an extension cord, you can easily verify that the earth of a socket is connected with the earth of another one (take your kitchen socket as a reference): you must read 0 Ohm (note that it does not mean that the earth of the whole house is correct, you need more sophisticated device to test that). If you read infinity, you have an earth problem.

It would explain that you have no problem with batteries and in your kitchen. But you would have to repair that quickly for your security. :angry-screaming:
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Re: THR10C very loud hum/squeal

Unread post by Suncloud » Sat Apr 13, 2019 5:01 pm

Thanks a lot. A multimeter is on my tools wish list (a girl can never have enough tools!). I just had a look into my fuse cabinet. My wee flat has 7 fuses, divided into two groups: Kitchen, bathroom and high voltage kitchen appliances, and the rest. So I don't think the sockets in the livingroom and kitchen are connected to start with. Both groups have separate residual current circuit breakers (hope that's the right word).

The guy in the guitar shop mentioned that I should check the socket in the kitchen. Apparently, humming from other than kitchen sockets is normal. I'm renting, btw, thus I can''t do any repairs myself. And if this is normal here then my landlord won't be willing to do anything either. I guess to prevent leakage/electroshocks this RCB is there.
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Re: THR10C very loud hum/squeal

Unread post by 314159 » Sat Apr 13, 2019 5:43 pm

Suncloud wrote:
Sat Apr 13, 2019 5:01 pm
Thanks a lot. A multimeter is on my tools wish list (a girl can never have enough tools!).
You can buy a cheap one for around 10 pounds or euros. It's very useful in a house. And you can also use it to test your batteries voltage, or your cables with the ohm-meter function if you have a bad contact.
Suncloud wrote:
Sat Apr 13, 2019 5:01 pm
I just had a look into my fuse cabinet. My wee flat has 7 fuses, divided into two groups: Kitchen, bathroom and high voltage kitchen appliances, and the rest. So I don't think the sockets in the livingroom and kitchen are connected to start with. Both groups have separate residual current circuit breakers (hope that's the right word).
No, the earth does not go to the fuses. It goes... to the earth! All the sockets must be connected to the earth, and one way to do that is to connect the earth of each socket to the earth of another one with a green/yellow cable, until you arrive to the earth of the flat or house.
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Re: THR10C very loud hum/squeal

Unread post by Suncloud » Sat Apr 13, 2019 5:53 pm

Thanks a lot. I'll get my tools out and have a look if the earth cable is actually connected to the socket, or maybe covered in plaster or paint like all the cable-ing in one of the ceiling outlets. I'd rather do this when I'm not at risk of being overtaken by sunset though and will wait until tomorrow :)

Is there otherwise a way to earth an amp somehow? Some of my electrical appliances (a Japanese travel rice cooker comes to mind) have their own earth cable.
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Re: THR10C very loud hum/squeal

Unread post by Saul » Sat Apr 13, 2019 6:12 pm

Suncloud are you in France by any chance? It is quite common that the sockets in the kitchen will be earthed whereas the other sockets around the home will not be. If they are of the flat two pin variety that is. Mostly this is fine because they are intended for low voltage devices but of course if you plug something like a guitar amp into these sockets you will get a mains hum.

I know you don't like the thought of using batteries but a couple of sets of rechargeable's...under the circumstances might be a good investment ;)
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Re: THR10C very loud hum/squeal

Unread post by 314159 » Sat Apr 13, 2019 6:35 pm

Saul wrote:
Sat Apr 13, 2019 6:12 pm
Suncloud are you in France by any chance? It is quite common that the sockets in the kitchen will be earthed whereas the other sockets around the home will not be. If they are of the flat two pin variety that is. Mostly this is fine because they are intended for low voltage devices but of course if you plug something like a guitar amp into these sockets you will get a mains hum.
True, in "old" houses/flats you can still find two pins sockets !
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Re: THR10C very loud hum/squeal

Unread post by Suncloud » Sat Apr 13, 2019 6:37 pm

No, in the Netherlands. All sockets look the same, and the building was constructed about 3 years ago. It is possible that the earth cable is not connected, thus that's something to look into for tomorrow.
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Re: THR10C very loud hum/squeal

Unread post by 314159 » Sat Apr 13, 2019 6:49 pm

Suncloud wrote:
Sat Apr 13, 2019 5:53 pm
Thanks a lot. I'll get my tools out and have a look if the earth cable is actually connected to the socket, or maybe covered in plaster or paint like all the cable-ing in one of the ceiling outlets. I'd rather do this when I'm not at risk of being overtaken by sunset though and will wait until tomorrow :)
Yes, it can be that kind of little problem, just a bad contact. Perhaps a screw to tighten. You're right, it's better to do it during the day! cause it's better to turn off the power before looking into your sockets...
Suncloud wrote:
Sat Apr 13, 2019 5:53 pm
Is there otherwise a way to earth an amp somehow? Some of my electrical appliances (a Japanese travel rice cooker comes to mind) have their own earth cable.
I am not sure the problem is the amp itself. My THR10 is not connected to earth: it is connected with a simple jack (+-) to an AC/DC Adapter, which is connected to the earth (3 pins). So I guess the humming is coming from the Adapter: there is probably parasitics in the DC current that it supplies.
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Re: THR10C very loud hum/squeal

Unread post by 314159 » Sat Apr 13, 2019 8:06 pm

You can also have a look to this post about AC/DC adapters and THR10:
viewtopic.php?f=135&t=5546&p=62193&hilit=hum#p62158
and:
viewtopic.php?f=135&t=5546&hilit=hum&start=30#p62195

It seems there was a defect in the early THR10.
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Re: THR10C very loud hum/squeal

Unread post by Suncloud » Sun Apr 14, 2019 9:41 am

Yep, that hum was only related to the first adapters of the THR10, but not the later 10C. Plus I ordered a completely new 10C and that unit did exactly the same. It's got something to do with the wiring/sockets in my flat. Did a few more tests this morning and found out that all sockets on the kitchen group are fine (kitchen, bath, loo) and all on the other one (livingroom, hall, bedroom) are not. I'll ask my neighbours if they have a multimeter to figure out whether the sockets are actually earthed properly before I start taking things apart here (of course with fuse taken out!). Sigh!
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Re: THR10C very loud hum/squeal

Unread post by 314159 » Sun Apr 14, 2019 10:29 am

Suncloud wrote:
Sun Apr 14, 2019 9:41 am
Did a few more tests this morning and found out that all sockets on the kitchen group are fine (kitchen, bath, loo) and all on the other one (livingroom, hall, bedroom) are not.
OK, so it seems the earth is good in rooms with water, where the danger is maximum. But it's still a problem for the other rooms... :confusion-confused:

In the meantime, you can just use an extension cord from a water room to the room where you play... :music-guitarred:
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