RF/EMI Noise and 11 Rack

[vmaxvmax]

There have been a few sporadic postings on this issue and it was touched on in a reply to a recent thread about another noise issue.

I think that this subject merits its own thread and a discussion, if only to cultivate other views, experiences and solutions.

I have found the 11r to be more liable to RF or EMI noise than some other gear.

It will often display this type of noise when other rigs in the same conditions at the same time and place don't.

The noise generally presents as a high pitched hiss or whistle centred at around 5800 htz.

I think that the 11r is very susceptible to local conditions - i.e. poor quality mains, lighting and other sources of interference (possibly including mobile 'phones). Might even depend on what your neighbours are up to or how good their electrical systems are.

It makes no difference if the 11r is connected or not to the computer or wether or not the computer is on. Proximity or angle to the 11r, computer and or display screens make no difference either.

It also seems that some active guitar electronics are less susceptible. I believe your body can become an aerial for noise to be picked up by the guitar circuit - the noise may diminish or get louder depending on proximity between you and the guitar rather than between the guitar and the 11r.

One of my guitars is a USA Strat to which I fitted a Graphtec Ghost saddle pickups active system. That circuit display no noise in the same conditions when other guitars do.

I find that fully screened circuits with humbucker pickups tend to present only marginally less Rf/EMI noise - but still an objectionable amount.

I used to repair guitars (now retired!) so I know about wiring and shielding etc. All of my guitars are properly wired and fully shielded with copper foil or shielding paint. Internal cabling is, whenever possible, screened and earthed. External cables are of course good quality!

High gain and high treble content settings heighten the problem.

I have found that when the noise presents (here, normally during the afternoon), it is best to strap a conductor to yourself and earth on your system. An earthing strap similar to those used when 'messing' about with semi-conductors etc will do the job. Strap it to your ankle and you might also need to extend it to reach your earthing point without it being in the way. That completely kills the noise!

It might be worth investing in isolating transformers...

Oh and last of all - when I use my old Dual Diversity Nady wireless system I get no noise! So I tend to use that during problem periods and live with the slightly different signal presented to the 11r.

I hope these comments might help or resonate with others...

[fly_with_v]

Using a Furman, Monster Power, or other isolating power unit will go a long way. I purchased an APC G5BLK power filter and 99% of my problems are gone.

[musicman691]

Originally Posted by vmaxvmax

There have been a few sporadic postings on this issue and it was touched on in a reply to a recent thread about another noise issue.

I think that this subject merits its own thread and a discussion, if only to cultivate other views, experiences and solutions.

I have found the 11r to be more liable to RF or EMI noise than some other gear.

It will often display this type of noise when other rigs in the same conditions at the same time and place don't.

The noise generally presents as a high pitched hiss or whistle centred at around 5800 htz.

I think that the 11r is very susceptible to local conditions - i.e. poor quality mains, lighting and other sources of interference (possibly including mobile 'phones). Might even depend on what your neighbours are up to or how good their electrical systems are.

It makes no difference if the 11r is connected or not to the computer or wether or not the computer is on. Proximity or angle to the 11r, computer and or display screens make no difference either.

It also seems that some active guitar electronics are less susceptible. I believe your body can become an aerial for noise to be picked up by the guitar circuit - the noise may diminish or get louder depending on proximity between you and the guitar rather than between the guitar and the 11r.

One of my guitars is a USA Strat to which I fitted a Graphtec Ghost saddle pickups active system. That circuit display no noise in the same conditions when other guitars do.

I find that fully screened circuits with humbucker pickups tend to present only marginally less Rf/EMI noise - but still an objectionable amount.

I used to repair guitars (now retired!) so I know about wiring and shielding etc. All of my guitars are properly wired and fully shielded with copper foil or shielding paint. Internal cabling is, whenever possible, screened and earthed. External cables are of course good quality!

High gain and high treble content settings heighten the problem.

I have found that when the noise presents (here, normally during the afternoon), it is best to strap a conductor to yourself and earth on your system. An earthing strap similar to those used when 'messing' about with semi-conductors etc will do the job. Strap it to your ankle and you might also need to extend it to reach your earthing point without it being in the way. That completely kills the noise!

It might be worth investing in isolating transformers...

Oh and last of all - when I use my old Dual Diversity Nady wireless system I get no noise! So I tend to use that during problem periods and live with the slightly different signal presented to the 11r.

I hope these comments might help or resonate with others...

Of course high gain and treble boost will exacerbate any apparent noise problems. So will single coil pickups and some onboard electronics. Strat pickups are some of the worst, right along with Gibson P90's.

Using a grounding wrist strap to 'cure' your problem isn't the way to go. If that is indeed happening you had better get ALL your grounding checked. Not just your guitar or amp but your house wiring as well. And don't forget the public utility wiring outside the house. There might be a faulty ground out there. If you have a power transformer on a pole nearby those can and will radiate noise. You say your noise problem is bad during the afternoon - you might want to take notice if there's humidity changes going on. Notify your utility company that you're having noise problems - they may be able to help you.

As a ham radio operator I've run into all kinds of noise problems, solved them and helped others to take care of their issues. You'd be surprised to find out where electrical noise can come from, whether radiated or conducted. You have flourescent lights? Noise source. Light dimmers? Ditto. Touch switch lamps? Big time noise generators. Most modern power supplies in electronics (especially computers) are switching power supplies and those are notorious noise generators.

In short the 11r is no more liable to emi/rfi than any other piece of electronics equipment. It's the noisy environment that we're in.

[TieDyedDevil]

Originally Posted by musicman691

It's the noisy environment that we're in.

That's for sure.

A bit off-topic, but I thought this was remarkable at the time:

Mrs. TDD and I used to go to Burning Man. For those of you who don't know, this is an event held in the middle of the Nevada desert, miles from civilization (and electric utilities) of any kind.

On year I brought my guitar and a battery-powered amp. The first time I turned this rig on in the middle of the desert, I thought it wasn't working. No noise. None. Nada. I pulled the instrument cord from the guitar. Nothing. Put my finger on the tip of the plug. Still nothing.

Of course, when I rolled up the volume on the guitar and played everything was as expected.

[vmaxvmax]

Originally Posted by musicman691

Of course high gain and treble boost will exacerbate any apparent noise problems. So will single coil pickups and some onboard electronics. Strat pickups are some of the worst, right along with Gibson P90's.

Using a grounding wrist strap to 'cure' your problem isn't the way to go. If that is indeed happening you had better get ALL your grounding checked. Not just your guitar or amp but your house wiring as well. And don't forget the public utility wiring outside the house. There might be a faulty ground out there. If you have a power transformer on a pole nearby those can and will radiate noise. You say your noise problem is bad during the afternoon - you might want to take notice if there's humidity changes going on. Notify your utility company that you're having noise problems - they may be able to help you.

As a ham radio operator I've run into all kinds of noise problems, solved them and helped others to take care of their issues. You'd be surprised to find out where electrical noise can come from, whether radiated or conducted. You have flourescent lights? Noise source. Light dimmers? Ditto. Touch switch lamps? Big time noise generators. Most modern power supplies in electronics (especially computers) are switching power supplies and those are notorious noise generators.

In short the 11r is no more liable to emi/rfi than any other piece of electronics equipment. It's the noisy environment that we're in.

Thanks for your reply.

As for the 11r being more susceptible to noise or not - I have the proof here - as I said in my first post, I can have my other rigs on at the same time and the 11r presents the RF/EMI noise while my rack system and my valve combo don't. It makes no difference if my computers or displays are on or off. The noise presents when the guitars are next to my body and diminishes as I move away from the instruments - leading me to believe that my body is acting as an aerial/conduit for the 5800 hz noise which in turn leads me to believe that the noise is possibly airborne! Thank goodness the wireless system removes it.

My house has modern wiring and I have done continuity checks etc - earth is fine. No dimmers etc.

I do periodically get DC offset on the mains which I have stopped with a DC blocker circuit. I think that one of my neighbours might be using an old appliance of some sort which I know can cause the offset - but the frequency of its occurrence is completely random and until I fitted the DC blockers, the offset would only show up as mechanical noise in the windings of the toroidal transformers in my active monitors. However, most likely a red herring and completely unconnected to the 5800 hz 'whistle'!

The electricity company here in the south of France does not have a great reputation for listening... Ambivalent fatalism - a shrug of the shoulders...

[TieDyedDevil]

Just playing with some numbers:

44100 / 8 = 5512
48000 / 8 = 6000

So, 5800 Hz is *approximately* the 8th subharmonic of both a 44.1KHz and 48KHz sampling rate.

If this *is* related to the sampling rate of your 11R, then *maybe* you'll be able to detect a difference in pitch by changing the sampling rate. If my math is correct, it's only about a 10 cent (1/10 semitone) difference...

[musicman691]

Originally Posted by vmaxvmax

Thanks for your reply.

As for the 11r being more susceptible to noise or not - I have the proof here - as I said in my first post, I can have my other rigs on at the same time and the 11r presents the RF/EMI noise while my rack system and my valve combo don't. It makes no difference if my computers or displays are on or off. The noise presents when the guitars are next to my body and diminishes as I move away from the instruments - leading me to believe that my body is acting as an aerial/conduit for the 5800 hz noise which in turn leads me to believe that the noise is possibly airborne! Thank goodness the wireless system removes it.

My house has modern wiring and I have done continuity checks etc - earth is fine. No dimmers etc.

I do periodically get DC offset on the mains which I have stopped with a DC blocker circuit. I think that one of my neighbours might be using an old appliance of some sort which I know can cause the offset - but the frequency of its occurrence is completely random and until I fitted the DC blockers, the offset would only show up as mechanical noise in the windings of the toroidal transformers in my active monitors. However, most likely a red herring and completely unconnected to the 5800 hz 'whistle'!

The electricity company here in the south of France does not have a great reputation for listening... Ambivalent fatalism - a shrug of the shoulders...

Nothing your neighbor is doing will cause a DC offset to the AC mains. How do you know you're getting an offset - are you watching it on an oscilloscope? If so you need to use a transformer to isolate your scope from the AC mains. And don't try and measure DC offset with a DVM set on DC - won't work.

[vmaxvmax]

Originally Posted by musicman691

Nothing your neighbor is doing will cause a DC offset to the AC mains. How do you know you're getting an offset - are you watching it on an oscilloscope? If so you need to use a transformer to isolate your scope from the AC mains. And don't try and measure DC offset with a DVM set on DC - won't work.

I didn't need to measure it - it was obvious and confirmed by its complete removal using a 'blocker'. Here is a great article on the problem and its solutions - http://sound.westhost.com/articles/xfmr-dc.htm#intro

I think the problem is more common than might be expected because it is not a problem unless your toroidal transformers are playing up... I read somewhere that toroidal transformers designed for use in the USA at 60 hz can sometimes be an issue here in Europe with 50hz mains if the transformers are running near saturation. My Event monitors are USA made. I didn't have the problem back in the UK though!

Your thoughts and ideas are most welcome as what I know about electronics and electricity are limited to my logic and my upper school days doing physics and maths - enough to be dangerous!!!

To TieDyedDevil, mmm... I'll try altering the sampling rates and see what happens - who knows might be clock related?

[musicman691]

Originally Posted by vmaxvmax

I didn't need to measure it - it was obvious and confirmed by its complete removal using a 'blocker'. Here is a great article on the problem and its solutions - http://sound.westhost.com/articles/xfmr-dc.htm#intro

I think the problem is more common than might be expected because it is not a problem unless your toroidal transformers are playing up... I read somewhere that toroidal transformers designed for use in the USA at 60 hz can sometimes be an issue here in Europe with 50hz mains if the transformers are running near saturation. My Event monitors are USA made. I didn't have the problem back in the UK though!

Your thoughts and ideas are most welcome as what I know about electronics and electricity are limited to my logic and my upper school days doing physics and maths - enough to be dangerous!!!

To TieDyedDevil, mmm... I'll try altering the sampling rates and see what happens - who knows might be clock related?

Like so much in the diy/enthusiast audio realm I consider the 'solution' to the problem snake oil at best and dangerous at worst. Unless solidly built with proper component selection and isolation which most diy'ers can't do things can go very wrong with this guy's circuit and fast. I would NEVER use a circuit like this guy designed on anything that draws major AC mains current. At more than a couple of amps draw you're going to need diodes that are rated to carry more than the 3 amps of a 1N5404 diode and that's getting into the realm of heatsinking diodes. Proper heatsink design is a must here.

And your event monitors - if they are a recent purchase then they were not made in the USA as R0DE purchased the company in 2006 and moved production to Australia.

[vmaxvmax]

Originally Posted by musicman691

Like so much in the diy/enthusiast audio realm I consider the 'solution' to the problem snake oil at best and dangerous at worst. Unless solidly built with proper component selection and isolation which most diy'ers can't do things can go very wrong with this guy's circuit and fast. I would NEVER use a circuit like this guy designed on anything that draws major AC mains current. At more than a couple of amps draw you're going to need diodes that are rated to carry more than the 3 amps of a 1N5404 diode and that's getting into the realm of heatsinking diodes. Proper heatsink design is a must here.

And your event monitors - if they are a recent purchase then they were not made in the USA as R0DE purchased the company in 2006 and moved production to Australia.

Yes, point taken about audio dIY'ers and snake oil - though I am not sure what exactly what separates 'DIY'ers from professionals. Ive known many an amateur with more knowledge and abilities than so-called professionals - in most areas I can think of! Especially guitarists!

In fact my DC blocker was built with a different circuit incorporating a bipolar tranzorber (sort of one bidirectional super fast power zener/transient suppression device) and capacitor arrangement as opposed the the diode array shown in the article.

Just to be safe, my wife's son who is an electronics expert at the Culham Centre for Fusion Energy (part of the United Kingdom Atomic Energy Authority) built the circuit for me. Hopefully he should know...

My Events are USA models - the original 20/20 BAS v2's - others in Europe have had similar problems with transformer hum/DC offset (physical/mechanical in the windings/core). There was a thread somewhere, Gearslutz I think.

The main thing is that the blocker circuit works here in France.

I'd still like to get to the bottom of the 5800 hz noise on my 11r - unfortunately the hum has not presented for the last couple of days making it impossible to continue troubleshooting.