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cooknkpl · Location: USA Posts: 256

During recording, I hear radio in my headphones. It seems to be coming from the electric guitar becuz muting that channel kills it.

The setup is:
Electric guitar into Marshall head.
Out to DB4 direct box - direct into channel on Mackie 24/8

The troubleshooting is:
Tried diff channels
changed cables

This has happened before with diff guitars/amps. Any ideas?...kpl

Elameno · Posts: 64

I'm not sure how to eliminate this, but I know it happens on certain guitars. If you mess around with your tone or volume knobs when this happens you can sometimes "untune" your guitar from whatever radio frequencies you're picking up. Different pickup selections may also help.

Occasionally I'll get some Mexicans talking to each other over their CB radios overtop a Christian station with some preacher giving a sermon...the overlap of those two is an interesting thing to hear *LOL*. That happens on my Mexican Strat...kinda funny that it picks up Mexican's more than any other nationalities.

Elameno

Graeme · Member Location: Spain Posts: 4663

It might seem obvious, but what is happening is that something your setup is working (at least partially) as a radio receiver. Plenty of long wires around to act as an aerial and a poor connection (or poorly designed piece of circuitry) acting as a detector.

I seem to remember a discussion about this some time back - one where I imagine SteveG would have got involved - so it might be worth checking the archives.

In the meantim, I'd would try and isolate exactly where the problem is getting in. Set up as usual, then try changing the amp, guitar, etc. - one at a time - and see if anything changes. Also, try moving things around, it might reduce the level, but that's not really a practical solution.

IME, guitar amps are prime suspects when this sort of problem arises.

Havoc · Posts: 735

Check inputs (at guitar and amp) for bad ground connections. If that does not help, try a ferrite bead around the guitar lead close to the amp (like the ones on monitor cables).

Craig Jackman · Location: Canada Posts: 909

Also because electric guitar amps are generally apply HUGE amounts of gain to a signal, any worn cord that is picking up RF signals of any type is going to have those signals amplified as much as the lo-voltage guitar output. IME - not to disuade you from anyone else's - it generally the cord, followed by worn jacks on the guitar that are the source of the problem. I'd take a close look at the direct box too, as you are adding another pair of connections there which could be at fault.

the3jsgrve · Location: USA Posts: 442

I used to deal with RF problems all the time at live gigs. It turned out that when I traded in the ibanez distortion pedal I was using for a Marshall Guv'nor, the problem stopped. In the meantime, I often resolved the issue at individual gigs by geographically moving or rotating myself, the amp, or both. I've also heard of people running a short guitar cable from the output of the guitar into a direct box, then using a long mic cable to run the distance to another direct box near the amp, and a short guitar cable from there to the input on the amp. Needless to say, that sounded like a bit too much trouble for me at the time, but if I had this problem in the studio I wouldn't put it beyond the realm of things I might try.

Josh

VoodooRadio · Location: USA Posts: 3971

SteveG · Location: United Kingdom Posts: 6695

It's quite funny - everybody blames the input, but it's generally not the real cause at all. More than half the time this is caused by speaker leads, and output transistors that act as detector diodes to RF. How do you get to hear it? The overall feedback loop that's present in most amps takes care of this very nicely, feeding this demodulated signal back to the input... That's why on decent amps, you find a very solid looking coil of wire in series with the speaker, acting as an RF choke - to attempt to prevent precisely this problem.

Basically, whenever it happens, something somewhere is acting as a detector/demodulator - the root cause can sometimes be as simple as a dry joint, but at other times can be a right pig to sort out. Often as not, it involves a long piece of wire somewhere, but not always. And unfortunately it's often one of those annoying system problems where both bits of kit work fine on their own, but when joined together behave as though you've inadvertently joined them to a taxi rank.

Havoc's ferrite beads can sometimes work, (the principle's the same) but often, small RF chokes will do a better job - you just need to figure out where they need to go. In general, the particular topology of output transistors seems to make them particularly vulnerable to acting as RF diodes when they shouldn't be - and even input leads can pick up enough RF to get straight to the output transistors to be demodulated - it only takes one phase compensation cap in the feedback loop for this to happen - it will let all the RF directly at them! Often guitar amps, which tend to use less protected feedback loops, are the prime offenders here, because they tend to provide an easier path to the overall loop.

DeluXMan · Location: Canada Posts: 330

Hehe, those detector diodes can show up anywhere too, especially with badly maintained equipment and connectors. Everyone knows someone who knows someone who can hear their favorite radio station inside their heads due to a bad filling in their teeth. Big Grin

VoodooRadio · Location: USA Posts: 3971

Of course SteveG is right, however.... I have had occasions where 2 or 3 guitars plugged into the same setup did not display any problems and then 1 guitar would. It is in those instances where I narrowed the problem down to the guitar itself. The wire tricked worked in making the problem go away. I'm not an electrician and can't begin to explain exactly what transpires (I'm sure SteveG can!), but it worked and I've used it in more than one or two instances. Wink

SteveG · Location: United Kingdom Posts: 6695

And what do you think that Adobe management would make of this thread? Come to that, what do you think that they'd make of the whole hardware forum?

You don't need to answer - this is a rhetorical question. You just have to think about it...

jonrose · Location: USA Posts: 2901

oooo! oooo! But I want to, Uncle Steve!
Heh! :D

Off-topic as hell, of course! If the discussions with Dorothy are any indication, this would be squished on Adobe's forums.

Something we'll have to get used to, I'm afraid.
Or not...
;)

Best... -Jon

(No, I haven't decided..... yet.)

ozpeter · Location: Australia Posts: 3200

Jonrose, I've commented on your last post here in 'Can we stop the adobe FUD please?' rather than hijack yet another thread....

- Ozpeter

DorothyK · Posts: 84

VoodooRadio · Location: USA Posts: 3971

As alluded to by several folks recently.... it is threads like this that (while having no direct correlation with the particular software being used) show how all encompassing this forum (and the members knowledge) is. Threads like this DO pertain to situations relating to the recording process. (as does threads about gain staging, impedance, etc) In this case, the user IS using the companies software but needs to address the initial signal. Sure, there are O/T threads that are seriously O/T, but they are the minority here. We've always managed to police ourselves to a certain degree, discouraging certain subject matters (i.e. politics, etc). If Adobe doesn't see it the same way, then I am afraid (again, as has been alluded to) it's a lost cause..... Disapprove

DorothyK · Posts: 84

Graeme · Member Location: Spain Posts: 4663

jonrose · Location: USA Posts: 2901

It seems to me that there's been a lot of "getting picky" about a lot of things here lately, and quite frankly, it's getting old, fast. I've had half a mind not to come back and read these forums, as it's really become rather depressing.

And quite frankly, that's a really sad state of affairs, because for the last few years, I have come here to help people and to throw in humor where I can.

I'm getting sick and tired of seeing this. I was hoping to give this forum a nice, dignified sendoff when it finally went away - But now I'm wondering if it's already time to leave...

:blackeye:

motorhead6 · Posts: 193

Shielding does wonders.

post78 · Location: USA Posts: 2887

motorhead6 · Posts: 193

I think Les Paul uses some kind of low impedance guitar line but I dont know how it works.

motorhead6 · Posts: 193

They are hard to find but they do make shielded speaker cables.

Graeme · Member Location: Spain Posts: 4663

distech1 · Posts: 12

I just read this thread today and I thought I might suggest one other possible cause of your un-wanted radio reception - THE MACKIE MIXER. It seems that Mackie, at least with the LAST genereation of VLZ mixers, had a little design - ahem, feature - that caused the inputs on the mixer to act like little envelope detectors. They picked up AM radio stations quite nicely - especially at night. This usually only happens when the input trim is turned up high (as I suspect it might be, as you are using a direct box). I do not know how old your mixer is, or if Mackie even bothered to correct this problem in later models. What I do know is that I have had to deal with this very problem at least four times - ALL of them with Mackie VLZ mixers made in the mid-to-late nineties. I do a fair number of medium-sized (less than 32 inputs) sound installations. I often use Mackie mixers because they are easy to use, cost-effective, and they generally last a good long time.

Don't panic, though - there is a fix for this. Somewhere around this house I still have a circuit schematic that the Mackie engineers faxed to me one time. This circuit is simple, inexpensive, and it can be wired into the shell of the connector - no need to open the mixer case. It is just a couple small choke coils and a capacitor or two - and it WILL get rid of the radion station. In a permanent installation, wiring this "fix" into the XLR cable end is not a big deal because those connectors will ALWAYS be plugged into the same mixer. If your setup is portable, I would suggest making some "barrels" (which you can buy from any Switchcraft dealer). These barrels just look like elongated XLR cable ends that have two connectors on them. Order them with one male XLR and one female XLR, and just wire the Mackie circuit into the barrel. Then you can insert one in line when you need it (I would make at least two of these). This will still pass phantom power and I don't think it degrades the audio (at least not when you consider the alternative). I wish I had that circuit schematic handy, but if you call Mackie tech support (the telephone number is on their website - www.mackie.com - or in the back of your owner's manual), they will probably just fax the schematic to you - and they will no doubt do it much faster than I could find that piece of paper. Just tell them the problem you are having - I am CERTAIN they've heard it before.

By the way, if it is NOT an AM radio station, but an FM one you are receiving, I would still suspect the Mackie mixer. There is usually a small AM component to even an FM broadcast and the mixer IS sensitive enough to pick this up (it can be quite strong if you live anywhere near the offending radio station's transmitter).

VoodooRadio · Location: USA Posts: 3971

I wonder if demographics have anything to do with it....? FWIW, I owned Mackie mixers since the early Tapco days (still have a Tapco laying round somewhere as well) and haven't experienced this phenomenon at all. I am presently running a VLZ series board (not VLZ Pro, which I didn't like the preamps on) and again... no RFI. Shy

MusicConductor · Location: USA Posts: 1524

We have a VLZ1604 and a VLZPro1604, and those radio stations stay away quite nicely. The Mackie we've had problems with, and that was prior to a needed complete re-wire of all house mic lines, was a non-VLZ 3208 recording board. I have no idea the vintage of that, but it was certainly older than "mid-nineties." Thanks for the info anyway, DisTech1, as someone with thornier cables will be grateful for the tip sooner or later.

SteveG · Location: United Kingdom Posts: 6695

THe RFI problems with Mackies go back to the earlier ones, not just the VLZ series. Jensen Transformers will tell you that there is a mod for Mackie 1604s that fixes what they overtly refer to as an 'RFI problem'. They produced a pdf about it which is here, available for all to see... but if you did what they were proposing to all the input channels, you would be able to buy a complete new mixer for the same money!

SoloTune · Location: USA Posts: 194

At the risk of straying a bit off-topic, this reminds me of many years ago in my younger days, when I did a short stint servicing alarm systems. We got a call from a woman saying her alarm box was playing the radio. I went to her house not knowing what to expect, but became a bit less skeptical as soon as I pulled up to her driveway and noticed that she lived directly across the street from an AM radio station.

Sure enough, the alarm box was playing the station with relatively good volume. A large solenoid/relay in the center of the circuit board was somehow demodulating the amplitude modulation right out of the air. It was a strange thing to see.

Can't remember what, if anything, I did to "fix" it. Smile

SteveG · Location: United Kingdom Posts: 6695

If you want a bit of a laugh, along similar [t:7585565730]lions[/t:7585565730] lines, you could always read 'Microphone picking up radio stations?'... and yes, it really is true! There is a bit more on the background to the lion thing here, BTW.

VoodooRadio · Location: USA Posts: 3971

ROFLMAO..... Thanks SteveG! I had forgotten all about the "Lion Tamer" story! Wink

the3jsgrve · Location: USA Posts: 442

Great story Steve! That's hillarious!

FatFingerTony · Location: USA Posts: 2

I had this issue too, heard an Opera radio station coming out of my Roland PortaStudio 01 whenever my guitar was plugged into it. (Nothing like hearing fat lady's singing behind a heavy metal guitar riff!) It was the guitar picking up radio station (a cheap Strat knockoff). I could walk around the room and "tune" in the station better. The solution was I ripped open the guitar's wiring cavity, removed everything, lined the cavity with shielding tape, re-wired the guitar with a single ground point NOT attached to the volume pot, (make sure the shielding tape is attached to the ground point) and the radio station went away. Cheap guitars make cheap radios, and unless the guitar is super expensive, it never has enough shielding. Another benefit to shielding guitars is more controlled feedback and a lot less 60cycle hum when using single coil pickups (my guitar has no noise no matter what pickup you have selected). I know you stated you tried different guitars and amps, but maybe the setup is causing all the guitars to act like antennae, maybe shielding one would help???

SteveG · Location: United Kingdom Posts: 6695

motorhead6 · Posts: 193

If you dont have an RF problem a shielded speaker cable might not make on iota of difference but if you have an RF problem, assuming that everything else is shielded, a shielded speaker cable will make the difference between night and day.

jonrose · Location: USA Posts: 2901

motorhead6 · Posts: 193

I dont know if this will fit you definition of substantiating but here goes. A wire is actually a very good detector. A detector demodulates an RF signal, particularly an AM RF signal IE CB radios or some HAM radios like in the 10 meter band and 11 meter band. To make things worse CB radio "operators" often use what they think are linear amplifiers, although they are illegal. Its illegal to transmit more than 5 watts on a CB. Some of these guys have thousands at their houses and hundreds in their vehicles which wouldnt be so bad if they were actually linear amps and they didnt over modulate them. These amps are far from linear in fact they arent even disguised as class A amps. They are class AB pure and simple which means they splatter all over the place and then on top of that these ignorant CBrs arent happy with less than 200% modulation which makes it even worse. A friend of mine used to turn on a 100 watt "linear" in his truck and talk while driving to my house. My stuff didnt even have to be turned on and my speaker cables would pick it up and play it pretty loud in my house. It would come through my doorbell (wire is a good detector) even and I dont mean from 100 feet away but more like a 1/4 mile. So the logic is that since a wire makes a good detector a shielded wire doesnt. Of course if you dont have an RF problem it doesnt matter. If you are close to a freeway you may have an RF problem because of the truckers.

Graeme · Member Location: Spain Posts: 4663

SteveG · Location: United Kingdom Posts: 6695

I would just like an explanation of how wire on its own manages to demodulate - that'll do me fine... ]:}

All of the possible true explanations for this effect were giver earlier - I think that somebody needs to find out how crystal sets and TRF recievers operate - because this provides the clue as to what's actually going on here - not strange CB radio effects.

motorhead6 · Posts: 193

{A piece of wire, by itself is no more of a detector than my cat is. Something has to demodulate the signal, so unless you have wires that act like diodes, this isn't going to happen.}

Actually if they act like ANY non-linear device.

motorhead6 · Posts: 193

Steve G I dont think any kind of reciever would cause the problem.

SteveG · Location: United Kingdom Posts: 6695

motorhead6 · Posts: 193

I know the theory but my ears werent lying when I heard a CB on my doorbell more than one time. And they werent lying when I heard a CB through equipment that wasnt turned on either.

motorhead6 · Posts: 193

Actually I couldnt swear that the equipment wasnt turned on just that I wasnt playing any music through it.

SteveG · Location: United Kingdom Posts: 6695

Oh, these signals all obey the Laws of Physics - but not neccessarily the ones you think. We've had taxi radio coming out of toasters as well - but they aren't strictly demodulating the signal at all - and it's not the wire properties that cause this - it's brute amplitude modulation force. If you spend any time at all near enough to transmitters, you will find that the local field forces near the PA are string enough to excite all sorts of strange effects in surrounding equipment, but it's the local direct-radiated modulation that causes this, not RF detection. It's just a larger scale version of how deaf-aid loops work - if you put enough audio into a loop (no RF needed) then, you can pick it up easily within the loop. If you can get enough modulation current flowing in a transmitting aerial, then the same thing happens - and it's pretty easy to pick up.

The difference usually with the guitar signals is that there isn't a transmitter anywhere near, and that demodulation is taking place. But getting anything with a loop or a coil in it to resonate in sympathy with a high-slope EM field isn't that difficult at all if there's enough power available, and if a guitar is subjected to the same stimulus (CB radio next to it) then it's going to exhibit the same symptoms too. But this is rare, and usually pretty easy to detect. The usual case, as I said, is the one outlined earlier...

VoodooRadio · Location: USA Posts: 3971

Growing up, we had a "ham" operator living a couple of houses down. He used to totally "take over" the television when he was broadcasting. My dad got into CB radioing for several years and had a 1200 linear and a couple of sets of "beams" mounted on a tower in the backyard. I used to swing the beams straight at the guys house, turn on the linear and lock the mic and play guitar for him!! Shock

jonrose · Location: USA Posts: 2901

Well, both of you doing something illegal probably wasn't the best idea... But I'm sure it was fun. ]:}

You do know that, by law, that operator was/is obligated to (within reason) take remedial action for any interference they might cause, right? Their license depends on it. Just information for future reference... ;)

Best... -Jon

VoodooRadio · Location: USA Posts: 3971

Yea, I know that now... this all transpired when I was a wee teenager. My Dad would call him and he would promptly quit. He was the individual that got my Dad interested in CB/Sideband. My folks didn't realize that I was "jam'n him out", I would do it whenever Mom and Dad were out of the house. I would crank up and within a few minutes the phone would start ringing. I would just ignore the phone and run through all my favorite Ted Nugent songs!! ;)

BTW, even though he was an older fellow.. he really like Ted Nugent (at least he was always listening to it when I was around!) :O

post78 · Location: USA Posts: 2887

motorhead6 · Posts: 193

BTW I do have a fairly good idea of how most radios operate.

Sincerely,
KD5NR

jonrose · Location: USA Posts: 2901

I think what was being attempted was to convey the idea that shielded speaker cable is in the grey-area of diminishing returns...
8)

Best... -Jon

hishopper · Posts: 20

Two words: Nylon Strings.

Just kidding.. yes I read his setup. It's a joke!@!

motorhead6 · Posts: 193

I think what was being attempted was to convey the idea that shielded speaker cable is in the grey-area of diminishing returns...

I agree that in most circumstances it would be.