High “whistling” noise from my guitar/bass amplifiers in my home recording facility

[Bad Disciple]

Hi Dave,
I checked and yes, 1uH is the same as 1mH. Now, box finished and... for my surprise and frustration, it doesn't help, the "whistle" noise remains the same, not even diminished! I took care to meticulously examine your drawing and make correctly all the connections (I've also put isolations to exclude short circuiting). I also measured each and every connection with my Ohm meter and it's ok, 000 at 20k.

In fact, even with only a plug -without a cable- plugged in the amp, the noise is captured! Now, in some cases, IF I touch the mass with a grounded cable (attached to the ground pin of my mains), the noise dramatically diminishes (but still heard together with a "heshsh..." at volume turned higher). But mind that the amp WITHOUT any cable or plug plugged remains absolutely quiet.

I'm afraid, the problem goes further on to unknown directions... Do you have any other idea? What about making a kind of a "Faraday cage" around a cable and ground it to earth? I know, the idea of one-end-bond shield is a kind of it, but it didn't help either. Finally, I'm not sure is it an RF emission or isn't it a "polluted" electricity coming to my house? I tested on all the floors of my house and the noise is always the same.

 

[ecc83]

No! One "mu" or micro H is 1000 X smaller than one milli H! Its reactance or "stopping power" to RF is only 1/1000th.

Then, ten out of ten for the V short back to back jack plug but you MUST shield it! Wrap it with gaffer tape or similar then a layer of HDuty turkey foil, tape to finish but make sure the foil is bonded to the jack sleeve.

From you further comments it seems you might have an earth/grounding problem in the house?

Dave.

 

[ecc83]

Just thought of another test. Take a screened jack plug with no cable in it and insert into to amp. If THAT whistles I would bet the noise is mains borne, it does not get into the circuits until the input short is opened.

An amp with an "empty" screened jack in its input will be noisy, hiss and a bit hummy but it should not make the noise you get.

Dave.

 

[Bad Disciple]

Ok, I shielded the short plugs as you suggested and the following happens:
When the short (shielded) plug-to-plug is plugged alone into the amp it whistles (!);
When I add the filter box it DOESN'T whistle (!);
When I add the cable from the guitar into the filter box... it whistles again (and it is a good quality cable) !

The other test, just one screened plug with no cable, plugged into the amp DOESN'T do ANY noise, absolutely quiet.

So, recapitulation of the previous points:
1. My house is 15 years old, and I had asked the builder to make good grounds to all mains.
2. One year ago, the electricity company came to dig in the whole street to install some new kind of installations. Could there not be a mistake made by someone poorly qualified among the workers?...
3. I've tested my THREE tube amps and they all whistle when plugging a cable (with or without the guitar).
4. The whistle is present everywhere in the 3 floors of my house.
(last tests pics added)

Would you recommend other values to the inductors or capacitors?

 

[ecc83]

Get those 1mH inductors. When you come to fit them, take the jacks out of the tin and please post pictures of the contact side of the jacks.

I THINK you have it wired correctly but I cannot see for sure.

Dave.

 

[ecc83]

Holy excrement on a cracker! That is (uiavmm) a Series One 45 combo!
This is odd because the S1s have very good (toroidal, common mode bifiliar wound ferrite inductor LC if you want the technicals!) input RF filtering. In fact I have one such my hand.

I am rather relieved (but sorry for you!) that you have the problem with other amps since this indicated a very strong RF field is at work. I have never had a case of RFI with a Series One before. Had a guy who live on the coast next to a "secret" naval installation who was having trouble with an Artisan (iirc) some years ago and I built and sent him a filter much like yours. The %$$£"R never came back to me!

Might be worth an email to Blackstar but since the other gear is affected I doubt there is much they can do.

Dave.

 

[Bad Disciple]

Yeahhh...... as you say, and 1000 thunders in addition!!!... My good Blackstar S1 45 it just kicks asses and blows minds, man!

So yes, all three of my amps capture the same "whistle" and everywhere in the house.

Now here few more details that might help for detecting a solution.
I asked a neighbor who is in the municipality and he said it was NOT the electricity company but the GAZ company that buried some new installations when they dug in the whole street! That might be an indication!

Another test I did was through a DI box:
-So, a normal good quality cable to the DI box IN -- a XLR-to-unbalanced cable from OUT -- to Amp => and "whistle" is present (!)
-But, IF I press the DI box 'attenuation switch' from 0dB down to -30dB, the "whistle" disappears (!) but of course the sound goes low in Volume... while a "heshsh" noise is added and remains even if the guitar Volume is down to "0"!
-If I include in the chain the Filter box (either after or before the DI box) the results are the same, no difference - but that filter box is not correctly made yet!

I double checked about the inductors and those pumpkins in the (only) big electronics store in town told me they didn't have the 1mH chokes so they gave me... 1μH (micro) which as you say is x1000 lower value! I tried to order 1mHs with Maplin but they deliver only in the UK !! So I must find an online store in France or the Netherlands maybe to order them, as Belgium is the kingdom of a very slow-motion and slow-mind mentalities. (Myself luckily am not a Belgian!).

One thing is sure, something really godforbidden has happened till here. But I really appreciate very much your help, Dave! If you ever need some support related to "pumpkinland" Belgium, count on me then.

 

[ecc83]

Let me see if Maplin have them in stock here (10 mins away in car) and if they have PM me with an address and I will air mail them to you.

Call it a retired Blackstar tech's goodwill gesture.

Dave.

 

[ecc83]

Yes Maps tell me they have two in stock and I shall pick them up first thing the morrow.

Dave.

 

[Bad Disciple]

Let me see if Maplin have them in stock here (10 mins away in car) and if they have PM me with an address and I will air mail them to you.

Call it a retired Blackstar tech's goodwill gesture.

Dave.

Dave, you are a giant man! I will have to do something to thank you for that gesture! Ok, first my address.

Then I must pay you the cost, so give me your banc account. Or if you want to taste top quality Belgian chocolate instead, I'll need your address to send you a small pack!

 

[techplayer]

Hi:
I don't know if you are still having the problem, but if you are, try this-unplug your computer from the wall socket. If the whistling goes away, the problem is from the computer power supply, and sometimes installing a ground lift adaptor on the computer (NOT THE AMP) can solve this problem.

 

[techplayer]

Whistling sound

Hi: Sometimes a computer power supply can cause the problem you are describing. Try this--with the amp on and making the whistling sound, unplug your laptop from the wall socket. If the whistling goes away, the problem is caused by the computer power supply, and may be corrected by installing a ground lift adaptor on the computer (NOT THE AMP).

 

[Bad Disciple]

Hi: Sometimes a computer power supply can cause the problem you are describing. Try this--with the amp on and making the whistling sound, unplug your laptop from the wall socket. If the whistling goes away, the problem is caused by the computer power supply, and may be corrected by installing a ground lift adaptor on the computer (NOT THE AMP).

Hi and thank you for your feedback. I have tested that, I have tested everything, even stopped the power with the breakers in the whole house and left only one wall socket (so nothing else left connected to work)... with three different tube amps and different guitars, and different cables... and that "whistling" noise is always present. If I unplug the cable, it disappears.

 

[Bad Disciple]

Get those 1mH inductors. When you come to fit them, take the jacks out of the tin and please post pictures of the contact side of the jacks.

I THINK you have it wired correctly but I cannot see for sure.

Dave.

So, I connected the new inductors, correctly (pictures uploaded) and... the "whistle" is still there even STRONGER! I even capture a radio station with one of my guitars when using a high gain on the amp!

So, I did two other tests:
1. I took one of my amps and a guitar out of my house with a long mains extension (20m) from my house and made a tour in my neighborhood around 3-4 houses away, in front, right and left from my house. The "whistle is always present EVERYWHERE" and especially when close to where the GAZ company dug last year to put the new installations (so it was not the electricity company). But the "whistle" augments also when close to the TV cable distribution boxes (they are in front of each house here).
2. I also took my amp with a guitar to a friend's who lives in another area. There was NO "whistle" (like it was before in my house).

My last hope maybe is to find a sort of a METAL flexible tube to put my cable in it and ground it which would work as a sort of "Faraday cage" and possibly stop that horrible "whistle".

 

[ecc83]

Thanks for the chocs BD!
cannot quite see from the left hand picky but it does not look as tho' the shield is going through the choke?

Dave.

 

[ecc83]

Just read about the TV Diss box!! THAT could well be amping up a local radio station. The RF amps SHOULD have sophisticated band stop filter but everybody does CHEAP! these days!

Dave.

 

[Bad Disciple]

Thanks for the chocs BD!
cannot quite see from the left hand picky but it does not look as tho' the shield is going through the choke?

Dave.

You're welcome Dave.
You can open the filter and even unscrew the jacks to check if everything is correctly connected. I think so, as I precisely followed your drawing, but one never knows... I also measured each point after soldering and it all showed ok. Do you have another way for extended measuring?

 

[Bad Disciple]

Just read about the TV Diss box!! THAT could well be amping up a local radio station. The RF amps SHOULD have sophisticated band stop filter but everybody does CHEAP! these days!

Dave.

I have started an investigation with the 'Belgian Federal Posts & TV-distribution Company', I exposed the problem to them and I await a technician who will come and measure in my place and in the neighborhood. I also wrote mails to all neighbors and warned them that - as that emission of frequency is present in the whole neighborhood - it can be harmful for the health of our children, our youngsters and our own selves. Guess what, from +10 houses only ONE answered with concern!

Anyway, I only hope the tech discovers what exactly it is, then possibly find a more sophisticated PRO filter as you mentioned before. Or maybe you might have an idea of such one?

 

[Bad Disciple]

... ... ... ... but everybody does CHEAP! these days!

Dave.

Yeah... just a philosophical remark on that. We all and more sink in an "ocean" of a Financial Dictatorship led by a bunch of Invisible Dictators and their mindless puppets the politicians.

 

[ecc83]

"Anyway, I only hope the tech discovers what exactly it is, then possibly find a more sophisticated PRO filter as you mentioned before. Or maybe you might have an idea of such one? " Well, I only know a bit of the RF stop measures I used years ago. Way back in the day we had TV diss amps in flats and hotels and they were housed in stout diecast boxes with copper braid bonding straps on doors. I notice these day the companies use PLASTIC cabs and of course the kids kick the ***t out of them.

If you have one locally a "Ham Radio" club could be willing to help.

Dave.