Stand on metal to ground myself instead of a hum eliminator?

[rob aylestone]

This is NOT good. The mixer you have has an internal power supply, so wall wart failure is out of the question. There are two basic paths now. The mixer is faulty. To be honest, with A&H it is unlikely. The test is a simple one. Mixer and headphones =hum with nothing else connected, so take it somewhere else. Your house, but better, somebody elses. If it hums everywhere, it is faulty. It should be silent on its own. If taking it somewhere else produces silence, then without learning how to use the meter, get a proper electrician in. The ground of your basement might have AC volts on it, which it 100% should not. Worst case, it could even be a safety risk. Usual case, is that depending on your home wiring, and I am absolutely not an expert at US wiring codes, you have a bonding issue. Nowadays, certainly in the UK, ground is bonded to the neutral conductor, close to where it enters the building. Other property might not do this and have a ground rod for the safety ground. Losing these, or having a bad connection can let the neutral float up in voltage. It may only be a few Volts, but it can make audio device develop all sorts of issues. Worst case, it creeps up to your mains voltage, with potentially fatal results.

Testing just the mixer and headphones in other outlets should tell you if it is the mixer, or your mains. As death enters the scenario, a test meter would tell you all sorts, but NOT if you dont know how to interpret what it tells you ?

EDIT, your last sentence did not mention guitar, just mixer and headphones. If the mixer without guitar is silent, then take them to a friends. If silent there and not in your basement, then you are into screening your guitar with copper tape in all the cavities. This is also testable with another borrowed or owned guitar.

 

[ecc83]

I would like to just add to Rob's comments. The ZED 10 uses an internal switch mode power supply, i.e. no 60Hz transformer so that initial 60Hz spike HAS to come from an external source. Yes, transferring mixer, cans and guitar to another venue is a very good idea. The more so if the incumbent also has some audio gear. A mains outlet tester would also be very valuable, it can tell you if your mains polarity is correct but most importantly if you have an earth.

Dave.

 

[MC208]

I went ahead and picked up a Radial JDI direct box and connected it to the system. Hear attached file.

0-10 seconds: All outputs from mixer turned down all the way (-70 to -68 dB)
10-20 seconds: Guitar channel turned up to correct level, Ground disengaged (-50 dB)
20-30 seconds: Guitar channel turned up to correct level, Ground engaged (-55 dB)

As you can hear, the hum is still present, although not as loud.

 

[MC208]

I guess I just might need to get an electrician out to determine the problem, this is just nuts

 

[rob aylestone]

Have you tried taking it somewhere else? That will prove beyond reasonable doubt if it's the kit, or your house. Be aware that this kind of thing is outside the scope of many electricians. Hums and noises in audio equipment is rarely covered in any courses, qualifications and training. They can, however, do a variety of tests that will indicate anomalies in your supply system - but remember that they measure leakage current in mA, not dB. A safe system can hum, within specs and at that point, they usually blame equipment they cannot test!

 

[MC208]

I haven't yet, but I notice that when I move the guitar around to different positions, facing different directions, the hum can either get louder, or go away completely. So I tend to think it is some sort of interference. I just don't know what's causing it yet. I'll make a recording and post it here

 

[Slouching Raymond]

I once tried to play an electric guitar on a hotel stage.
It was hopeless. The stage was bathed in electrical interference (fan, air-con, or something), and the giutar picked it up and sent it to the amp.
All I could do was play on an electro acoustic guitar, which had a piezo pickup, rather than a coil. That was ok.

 

[TalismanRich]

Last week, our bassist was picking up a local AM radio station on his bass guitar. At first I thought it might have been my pedalboard (we are all going direct to a mixer), but when I hit my tuner, which cuts the signal off, nothing changed. I've been using my Joyo JW06, and have no issues with hum or noise. When we unplugged his bass, it went quiet. I suspect that the cable is poorly shielded, and that maybe causing grounding issues as well. He ordered a Joyo the next day. We'll find out if it fixes things. He said it made things more quiet when he plugged into his amp at home.

FrankD turned me on to that unit. Not very expensive but it has worked great the past 3 times I've used it. Plus it's been really nice not having to worry about stepping on a guitar chord. I don't know if a wireless unit will kill your noise but it might help if the cord is also contributing to the noise pickup.

The thing is, if you can move around and the noise goes up and down and disappears entirely, then it's not an electrical fault. It electromagnetic interference propagating THROUGH THE AIR, not through the electrical line. Your guitar and cable are acting as an antenna and receiving that noise. If you can find the generating source and shield that, it may help.

When Raymond went to his piezo pickup, it eliminated the reception because a piezo generates electricity when a vibrating string creates pressure changes on the crystal. A normal guitar pickup works by detecting the difference in magnetic field when the string vibrates which then generates a signal in the coil, and electromagnetic radiation can also be generate a voltage.

 

[ecc83]

Rich, what is the mixer and was the bass TRULY direct? No pedal first? I ask because RFI usually gets in a first stage transistor or IC. If the mixer is not picking up AM from any other source I suspect there is some sort of active device twixt bass and mixer.

It could, as you say simply be that the bass PUP cavity is not shielded but then it would be a pretty ***t instrument if so!

RFI is hard to stop sometimes unless you can get into the affected kit and fit some filters. These are just some resistors and capacitors. Ik and 100pf can work wonders! Even better is a series uH RF choke.

Dave.

 

[MC208]

Here's the recording I just made while moving the guitar around, turning it, etc.

 

[TalismanRich]

Dave, I don't know which model mixer Mike is using for what. He's got a old Tascam 488 and plus a 2nd newer mixer. He's got his drum set mic'd with 6 mics, plus 5 vocal mics and 3 guitar inputs available. I don't know which one the guitars feed. He's got a headphone distribution setup for 8, and it all goes into a Zoom H6 as a stereo feed. If it was my setup, I would ditch most of it and put in a Tascam Model 24!

Bill's bass is an old Guild JS2 bass which even has humbucking pickups. There are no pedals on his end, just a clip on tuner on the headstock. There's a cord direct to the instrument input of one of the mixers. That's why we were really surprised when he plugged in and when the faders were pushed up we clearly heard "News radio 84...." coming through our headphones. Unfortunately, the radio station is a 50,000 watt AM station, and the towers are about 2 miles down the road. Like I said, I suspect there may be some guitar cable issue at play here.

Heck, I was even playing my new H-530 with P-90s which are single coils, and there's NO shielding inside a hollow body guitar, yet I didn't have a bit of a problem.

 

[TalismanRich]

Here's the recording I just made while moving the guitar around, turning it, etc.

So what were you close to at 1:33 seconds? At 1 minute you were quiet, at 1:33 you had LOTS of noise. Something around there is putting out interference. That's a CLUE!!!

 

[MC208]

There are some track lights kind of like this above the area where that loud hum comes in at 1:33. I certainly noticed this as well. However, when I move the guitar closer to them towards the ceiling, the noise lessens. The noise is greatest about halfway between the floor and ceiling. I should also note that the track lights were off during that recording. So it doesn't make a difference if they're on or off actually.

 

[ecc83]

Dave, I don't know which model mixer Mike is using for what. He's got a old Tascam 488 and plus a 2nd newer mixer. He's got his drum set mic'd with 6 mics, plus 5 vocal mics and 3 guitar inputs available. I don't know which one the guitars feed. He's got a headphone distribution setup for 8, and it all goes into a Zoom H6 as a stereo feed. If it was my setup, I would ditch most of it and put in a Tascam Model 24!

Bill's bass is an old Guild JS2 bass which even has humbucking pickups. There are no pedals on his end, just a clip on tuner on the headstock. There's a cord direct to the instrument input of one of the mixers. That's why we were really surprised when he plugged in and when the faders were pushed up we clearly heard "News radio 84...." coming through our headphones. Unfortunately, the radio station is a 50,000 watt AM station, and the towers are about 2 miles down the road. Like I said, I suspect there may be some guitar cable issue at play here.

Heck, I was even playing my new H-530 with P-90s which are single coils, and there's NO shielding inside a hollow body guitar, yet I didn't have a bit of a problem.

View attachment 150945

Hmm, it is not reckoned to be good practice to plug guitars into mixer line inputs because of the very low (for guitar) input impedance, not that I think it matters much for bass? I can only surmise that because of the relatively high source impedance of the bass, 10k min I would say, that is making the input of the mixer open to RF. Mics are of course 150-200R and keys and such 1k max but usually much less these days.
A good cable is obviously worth a try, also wind it on some clip on ferrite filters. One each end. Also a passive DI box as close to the bass as possible and a good solid SHORT cable to it.

Did a lot of RFI stop work, was there when they 'invented' those pesky silicon planar transistors!

Dave.

 

[TalismanRich]

The mixer has mic/Line/Inst inputs. They work fine, been doing it for years.