Noise, noise, noise

Greets ppl!

I bought a WD-7 Weeping Demon Wah this weekend, and plugged it in. First, it was cool. Yeah it's still cool. But I hear a tremendous amount of noise after playing for a while!
My gear is the following (in connection order): guitar (passive pickup)-> WD-7 Wah pedal-> AX1500G Multi-effect processor-> PC (SBLive)-> old SANYO HiFi AMP-> Speaker

I don't have a guitar amp, I like to use the given abilities of my PC (recording, MIDI stuff, etc.).

Of course, I did some testing. First, I plugged got out the Wah from the system. No noise. Then I began playing. Just some soft things, but then I turned on distortion. Played a while, no noise. Played a bit more no noise. Then I turned up the volume on the amp, and I heard the noise. It was a bit different than the one I heard with the wah. I heard it for a while then it was just gone. No noise.
I repeated the thing for a while and the noise came several times but the frequency of appearance was non deterministic. Just came, and gone away, and that.
I plugged the wah in again, and it was the same effect as without the wah but the noise was different, the same I've heard for the first time. It was like a vacuum cleaner, or some sort of that. And after that it was gone again. Played awhile, noise again, waited a while, gone again.
It came absolutely unpredictable, there was nothing spectacular before I heard the noise.

So I figured that the problem must be before the wah. Maybe in the pickups. I lowered the volume of the pickups to nil, and guess what? I've heard german radio chatter when I increased the volume to the max on the amp.

Any ideas what to do now? I checked the wah, and it has a constant gain when operating. I tried to decrease the input level of the wah (so that the input current of the opamp inside swallows the noise), but still noisy.

One of my cables is home made custom. It has a metal sheath shield, it should be even better than the Ibanez "noiseless cable".

So guys, if you have any ideas where that damn noise could come from please don't wait to tell it!
If you'd like to, I can send the "noises" in MP3. They're funny :) I think they may be characteristic to a source, if someone has a plethora of experience. Maybe they can help.

Thanks a lot.

well first of all remember what a wah is and what it does.

second get rid of any ground loops by plugging everything in to a signal power strip or even better a power conditioner.

Next turn off all fluorescent lights and CRT type computer displays as your pickups will pick up particle emissions from these sources.

If this doesn't work try shielding the cavity housing the electronics of the guitar.

Sometimes when you are recording it comes down to moving about till you find a spot that gives you less noise than the others.


Last resort is a noise gate though this will only serve to kill the signal to your amp during times when you are not playing.

I tried a switch power supply which does not pick up any noise, but it had no effect.

I have long time experiences with electron emitting displays. I changed my pc display to a TFT monitor. It has practically no electric emission. (I tested my gear a lot with an ordinary television - THAT was really like a vacuum cleaner.) So no sources like that.

This shielding sounds like a good idea. However I don't really have an idea how to do it. Should I place a simple metal plate onto the interior of the plate covering the electronics?

Well the funny thing is that before using this wah pedal, the noise wasn't really an issue. It simply wasn't too disturbing. So I didn't really care for the noise sources. I have a noise gate in my effect, but it affects this kinda noise only on the highest level - there it nearly cancels even the "normal" guitar sounds.

Moving around sounds good, but honestly I like sitting in front of my PC during practice. There I can control the backgrounds, drums, basses, etc.

My next idea is that my cable isn't very good. It may act as antennae... Or at least something HAS to work as antennae, since I get radio chatter!

Thanks for the advices!

you can get shielding kits from www.stewmac.com. Id get 2 as when I did the inside of one of my strats I ran out halfway through.

The real problem probably lies in your setup.

A HiFi is tuned differently to a guitar amp / speaker system. A guitar amp is engineered to output the frequency range of a guitar. A HiFi system has to cope with a much wider spectrum of sounds.

The wah is effectively cutting and boosting particular bands of frequency and with the boost in signal come a boost in noise.

A guitar amp, relative to a HiFi exhibits a natural cut in bottom end and top end frequencies. Because you are amplifying and reproducing a broader spectrum of sound using the hi fi stuff, up comes the noise.

My advice, get a pod and a floor board, run that into your computer or a dedicated guitar (or stereo amp if you have to) and you have power to play with.

Thanks for the advice about the shop. I'll try to find a similar store here in Europe :) I hope there is one.

About the amp problem you've mentioned. I use the built-in amp simulators of my multieffect. It is after the distortion block so if this would be the problem, the noise frequencies shouldn't even get into the PC. The main problem is that the noise frequencies are right in the middle of the wah-boosted frequency range!

I checked up the "average" guitar amplifier frequency characteristics some time ago and I've experimented wth my SBlive to make an EQ setting similar to a guitar amp. I even got that jump at 5kHz, but you know, these SW EQs aren't perfect. And the built-in stuff in the multieffect isn't so sophisticated either...

About the last sentence, there are some things I don't really understand (my english - I'm not the best in the acoustic slang). What is a "pod and floor board"? Does it have to do something with common earthing? (I'm just guessing. ;) )

Hm. I got an idea that MAY be right. What is clear to me, that there"s a strong noise source. This can affect my pick-ups, or the electrics inside the guitar.
The electric can be shielded as you have described earlier, but I think I could try to bind the strings together electrically, and binding them to the common earth of the pickups (or maybe just binding them together).
I don't know if I'm correct but this may work as a screening conductor, and so may decrease the noise recieved by the pickups.

Is this possible?

Pods are made by a company called line6 and they are (IMHO) the best thing since the invention of the tea bag. you can see them on line at www.lin6.com.

www.stewmac.com will also ship internationally so they may be worth a further look.

I am going to have a think about what you have suggested and get back to you. It has been a long day and my head feels like it is about too explode !

[font=trebuchet ms]For guitar shielding techniques and theory, check out the articles at GuitarNuts.[/font]

Ah, you mean THAT pod :D
Amp modelling is a funny thing :)

But I spent the night thinking. (Diff timezones.) Even in my dream I was cruising around guitar stores to find the answer, or sitting above the plannig table to find something out. So I just think that I gather my resources and try to build a thing similar to a noise gate. Well, the principle should be the same. I could make it digitally with a DSP, but that would be a daaamn long way, though I'm sure the best. Maybe later. Now I'm only planning on making a non-linear circuit.

But anyway, if you've spent thoughts about my idea, please tell me! We always learn, I'm grateful for every ideas!

Lordatthestrings: Thanks, I checked it, yet didn't find anything useful. They deal with deterministic noise subject to grounding, gear fault, etc. Mine is kinda radio related or MAY be related to ESD.

So, I think I got the idea now, though I feel it's a bit spooky. I found one of my electronics books. I remembered that I've learned about realization of non-linear circuits with simple opamps. And that's it, I found it!

Well actually I found it at the limiter circuit, which is made for DC operation, so this may be a serious difficulty. But I'm working on it. The other option is of course the digitalway. Get a DSP with an ADC on its input, set sampling rate around 15-20kHz (maybe even less), and just simply pick out the low amplitude frequencies, and make a conversion back. Just plain and simple.
I don't know it it could work well. Maybe I should try making it.
But first I'll go to the guitar shop, and buy a NEW, guitar cable. Because after some more testing I found out, that I get radio chatter EVEN when the input to the wah is shorted (pickup potmeter at 0 Ohms), and even that stupid high amplitude noise comes in at times. Next thing I'll try now is to remove my cell phone from my room till I play.
Be back with results.

I got the new cable. Theoretically it is a good quality, non sensitive cable. 15 feet long. But I connect it, and hear the same radio chatter. I think I'll just build that noise gate.

However, there's one bit of experience. If I connect my guitar to the wah pedal with the short "noiseless cable", and the wah to the effect with the long new cable, the radio chatter is gone. However, the screetching noise whihc comes and goes stochastically does not dissapear.

Regarding that, my idea is the following. The thing has to do something with my pickups. Somehow these extra noises are coming from them. Reason? When I touch the strings, it's not that loud anymore.
Other idea. Somehow I created a nice juicy loop with the cable, and it acts as a simple radio antenna. I don't know, I think, I'll check on is.

I'm going to disconnect my pickups to see what happens. If there's a problem with any of the pickups, this will at least reveal it.

Be back with results.

[font=trebuchet ms]Is your computer plugged into the same mains outlet as your stereo amp? I think you have a ground loop between these two machines.[/font]

Absolutely correct about that. There is a ground loop, but since now that didn't mean a problem. Could this cause the reception of the radio signal?
Anyway, I'll try connecting them into a different slot. (In audio applications I didn't have to deal with problems like that - until now of course.)

yep thats a ground loop !

So. Just to continue testing, I did the following. I turned the amplifier off. I used the "Line out" of the multieffect with a headphone. No result, the noise (the quasi-stochastic noise) was still there.

To check this ground loop effect, I disabled it. I disconnected my PC, and the amp from the mains. No effect, the noise was still there.

Don't think about this as a "hum"-like noise. It is not always present. I know that it will come, but I don't know when. After that I know that it'll be a daaamn loud noise for a while, but I know that it will disappear. NOT FADE, just simply disappear.

So I'll go through my cables once again. I have no idea. Maybe my wah is really faulty somehow.

Plugging Headphones into a "line out" is not the best idea as the impedance is all wrong.

The ground loop will only really contribute radio frequencies as it acts as a big antenna.

Is there anything particular that you do to trigger the noise ?

No, nothing particular, but in fact, as far as I remember radio traffic was lower when everything was disconnected. But the radio traffic is not the real issue here. The problem is the non-deterministic quite loud noise, which comes from Dunnowhere.

Well I made some measurements with a spectrum analiser on that sound. And I found that it is like a white noise on the frequ band of the guitar sound.
There's no triggering action. It simply comes, and goes.

The next thing I'll try is to take it somewhere else (out of the house - I tried in the living room - the same stochastic noise came). Ah, one more to the line-out. There's an output on the multieffect, which was designed for headphones. I used that one, so that should not present a problem.

Id start be sequentially removing one thing at a time from your chain including cables and go from there.

If you cant isolate it that way it is probably a combination of things. A power conditioner is probably a good idea. ART make one (4 x 4) that comes in at about 30 bucks.

I'm working on this. But the truth is, I'm afraid that it's something "in the air" I cannot really influence. However I plan to get to a rehearsal place with some amps, or just simply to one of my neighbours.
Just to see if the same noise appears there too. I'll be back with details.

Originally Posted by: Hankyaku.... Could this cause the reception of the radio signal? ...

[font=trebuchet ms]Absolutely! You may need to put an isolation transformer between one of the machines and the AC mains.[/font]