Odd amp/cab issues and a rant

[crochambeau]

To further elaborate on it:

Speakers don't produce self noise, which points hum squarely at electronics.

If this hum is shared on multiple amplifiers, it kind of steers us away from amplifier failure (doesn't rule it out completely, just really minimizes it).

I've come across hum issues in a few ways, first order of importance is to confirm your outlets are electrically sound (this is a SAFETY concern ~ and I see by your post it's okay). If you have floating ground or hot neutral swap, fix that shit before proceeding.

Now that your outlets are proven okay, are all outlets in use in your gear set up on the same breaker? There are noise generating phase anomalies that can occur if you're feeding interconnected gear from outlets on both sides of the single phase split, so, for troubleshooting you want to be feeding from one trough at a time.

[PeteeBee]

Reading crochambeau talk about amps and electricity makes me want a Rochambeau amp. Seems like some serious knowledge. I need to get back to the practice space and try to solve my phantom amp noise...

[crochambeau]

Reading crochambeau talk about amps and electricity makes me want a Rochambeau amp. Seems like some serious knowledge. I need to get back to the practice space and try to solve my phantom amp noise...

Hahaha, thanks!

Honestly, I've just been shocked a bunch of times. Nothing like getting that stuff hammered into you to really make it stick!

[ThurberMingus]

Petition for Rochambeau amps to become a thing?

[crochambeau]

I won't say it's not been contemplated. Problem is that raw materials cost of a proper amplifier is about what some paper spec equivalent amplifier that's been shit out of some factory costs retail, and that's before my time comes in. I don't feel like I've got the name recognition to go into say, the Science range of the market just yet, and to be honest - I'd be bringing something different into play, which involves a lot of R&D and unknown failure modes, which will certainly scare off some people. (I'm not going to elaborate on my topology, but I am 100% certain it would garner derision from the steadfast producers of classic style amplifiers, and eventual servicing would probably require my assistance).

I do plan to mosey about building such a thing for myself, but since it's a side project I can't go all in so it'll take forever.

That said, I appreciate your interest and will do more than just speculate on it.

[Jwar]

So took it to my parent house (my whole rig) and the same thing happened. My brother said it sounds like my cab is picking up noise from the electricity, but it's odd that it's happening everywhere. He suggested some kind power inverter but I don't know anything about them or really what the fuck he was talking about.

My stuff is all on one breaker for my home and one outlet. The last bit you said, I didn't understand? Maybe you could dumb it down? hahaha

[crochambeau]

The last bit you said, I didn't understand? Maybe you could dumb it down? hahaha

If you run everything from one plug it's a non-issue, but:

The main power feed to your house is ~ 230/240 volts with a center tap. The center tap is the neutral/return path, and it's electrically centered between the two hot lines.

Anything needing 230, like say your stove, is simply connected across the two hot lines which make the 220 volt service, and the neutral acts as your ground. To make 115 they reference the neutral line and ONE of the hot lines. If you take the front panel off your breaker box (do not actually do this unless you need to for some reason) you will see the two hot lines leap frog each other like this:



This means that adjacent breakers will be carrying hot AC signal that is 180 degrees out of phase with each other (because from the center neutral point as reference, as the 230 is rising the voltage is rising away from center on one leg and toward center on the other), and due to certain noise damping methods built inside of a lot of components adding these out of phase signals will do the opposite of null. They can make matters worse, but not always. It's the whole ground loop thing, total rabbit hole. People lose their minds over this shit. Tread lightly.

Does the cabinet hum with nothing connected? I'm guessing that's a no, it would take astounding levels of EMF to move a speaker cone and I would be seriously concerned about the health of people living in that environment.

What's your cable game? Nice shielded instrument cables up front & proper speaker cable out back?

If you turn the amp on, without an instrument plugged into it does it hum? Or is the hum a function of volume?

A little hum is not unusual, and leans towards insufficient filtering in the power supply, resistive or floating grounds inside the amp, unbalanced or poorly biased amplifier section (this usually just over taxes the power supply, but DC coupled solid state amps will also plant a bias voltage on the output, preloading your speaker with a little DC which will generally impact your sound quality for the worse), or over cooked preamp part. I'm sure there are more causes.

If you brother has an inverter you can try I'd say go for it. I've yet to have a line filtering doo-hicky fix a single observed problem in my world, but I might just be lucky/unlucky that way.

To recap: three amps have done this, same speaker cab? Is another test cab available? Cables good? Can you rule out input completely?

[popvulture]

I wonder if since you had the same issue at multiple places, it could be something with your amp being finicky about the power it's getting from the outlet?

In that case, maybe have a look at something like the Brown Box:

http://www.amprx.net/product.html

They are about $350, which ain't cheap, but I know more than a few people who've gotten good results from them. Plus they make your amp happier/healthier. Just thought I'd throw that out as a suggestion

[imJonWain]

To recap: three amps have done this, same speaker cab? Is another test cab available? Cables good? Can you rule out input completely?

second this^ , the issue sounds strange.. sounds dumb but is the cabinet speaker jack dirty or worn out?

[Jwar]

To recap: three amps have done this, same speaker cab? Is another test cab available? Cables good? Can you rule out input completely?

second this^ , the issue sounds strange.. sounds dumb but is the cabinet speaker jack dirty or worn out?

So just to respond to this part.

I have two cabs doing the exact same thing. They've done it with my Mesa Bass Prodigy, a Mig 50 and now a GK 1001 RB II. So two tube amps and a solid state. I've tried multiple different cables from bass to amp and they've been good up until this point, plus when I plus the same cables into my 10 watt amp (combo), there is NO issues at all. There is if the volume is too loud, but it's a baby amp and I'd expect that when hit with a large output from my active preamp.

I don't currently have a third cab, but perhaps I need to just buy one. Which sucks ass, but I'd rather it be a fucking cab than the power in my home. Maybe it's time to hit those Black Friday sales...if only I hadn't just spent 611 bucks on a gun yesterday (it was 400 off!!!!!!! What was I supposed to do??? NOT BUY IT??? ).

I've hit every damn connection possible with contact cleaner, but it still could be a dirty cab jack or even failing. I checked the solder joints and everything in the cab looks fine. No floating grounds or anything. Perhaps I over drove the cabs drivers since I've slammed them with so much dirt for the past three year but they are built to take a lot. I mean they are fucking powerhouse cabs. I've never heard of one taking a shit from too much dirt.

My bass has good shielding, but this occurs when it has not bass plugged in either or if I use another bass. So that's not the issue.

I really think it's the cabs, but it's bizarre that it could be both of them and my amp at the same times? Especially after three solid years with no issues.

So weird/annoying. I know I can just deal with the feedback/hum but if it is an issue, I'm sure at some point the cab will just go poof. So I'd rather figure it out and not go that route. I just don't get it.

[crochambeau]

In my experience, failure modes of speakers are as follows:

1) Less sound, as in, nothing.
2) Sympathetic rattles or pops that are frequency specific, these are typically cocked coils from misalignment (heat distortion) or bottoming out (brute force abuse), adhesion failure of coil (heat), or tear (abuse), or age related failings that have to do with materials (death to foam surrounds)

Is it 60 cycle hum? You can plant a hundred thousand dollars of line conditioning on your rig and it'll still spit out 60 cycles, because that's the mains' job. Conditioning may eliminate buzz and hash, but if it's hum look elsewhere.
Is the frequency higher? Like 120 cycles? If so, that's poor filtering inside your amp. If you have a lot of overs/unders on your power, maybe your PSU sections have been over stressed, which points toward looking into some conditioning (I still stand by my experience of never having had those things fix anything, but for preventative maintenance it's probably a good idea).

Maybe your cabs are just tuned to 60 hz, and you've become super sensitive about it? Are your fillings rattling? You hear this in your gear, do you hear it in others?

At least now if it continues to give you grief, you can just take it out back and shoot it. Sometimes looming threat does in fact make complaining gear STFU.

[lordgalvar]

Crochambeau always brings the knowledge...I think he is probably right on the money in snaking out the problem.

Just my experience:

I've had a similar issue lately with certain power supplies and my amp. I should note that LA power is terrible and it fluctuates immensely throughout the day (they are constantly rerunning wire out here...I'm guessing a lot of our problems are utility based in LA around 6pm at high draw time...nothing works right in my house).

Anyway, I recently got a pedal with a dedicated wall wart and it made my beta lead buzz louder than my guitar signal just plugged into an outlet on the same circuit. I've always had some hiss on that amp...but this was the worst ground noise I've ever had. Pissed off, I unplugged the pedal and the noise dropped back to normal (pedal was on what I thought was a different circuit). I went through and unplugged every wall wart/switch psu on the circuit (ran through like 4 rooms) and turned on the light...hum free. Grounding issues, but my plugs check out right with the tester.

Later, I was messing with two different PSUs (the one above too) and once I joined them to a common ground (the signal jacks), the less noisy psu fixed the noise. This was direct in. Same problem once I turned on my amp.

I know there has to be a broken ground some where now (the house is 85 years old...who knows?....I've ripped so many hidden boxes out of the house)...but I also accept that there is that mysterious "floating neutral" or whatever most likely at the street.

Glowing lights and all that stuff is a good indication.

Anyway, a while back I read about people that use ac/DC/ac converter boxes to clean their power for sensitive devices...supposedly it works, but is expensive.

If your MIG is like my MIG (I know the 50 and 100h are different amps), I wouldn't judge noise floor by that thing at all. Mine sounded different and hissed different in every damn outlet ever. It was really really influenced by grounding and different power. Significantly more than my sunn sorado. Haha.

[Jwar]

Nothing is rattling at all.

How do I tell the frequencies?? When you say over unders, do you mean the outlets? Like the way they are outlets are? I noticed this house has a bit of both, which isn't standard now. So weird.

I changed the decibel level on my cab to under 5 db, well actually well below that and then also tried it higher. It seems to get a tad worse higher. I tried the crossover switches, which allows you three different tonal options 5k, 4k, and 3k. The ONLY thing that doesn't seem to work properly on the cab is the horn reset button. It works well on one cab and not on the other.

I'm going to bite the bullet and go to GC today and see if they have a cheap cab to test. I don't even care if it's a good one. I've got to know if it's something with the stupid amp or cab or am I really the sensitive. If that's the case though, it's odd that my brother heard it too, but I guess it makes sense. I'm really sensitive to high frequencies which I attribute to over 20 years of bass playing and loud rock concerts, well plus shooting guns. My ears have been quite abuse.

When I play though, the cab sounds great. It's when I don't play and I'm fucking weird about that shit, I know that. I can't help it. It's my OCD. Sigh.

[Jwar]

Crochambeau always brings the knowledge...I think he is probably right on the money in snaking out the problem.

Just my experience:

I've had a similar issue lately with certain power supplies and my amp. I should note that LA power is terrible and it fluctuates immensely throughout the day (they are constantly rerunning wire out here...I'm guessing a lot of our problems are utility based in LA around 6pm at high draw time...nothing works right in my house).

Anyway, I recently got a pedal with a dedicated wall wart and it made my beta lead buzz louder than my guitar signal just plugged into an outlet on the same circuit. I've always had some hiss on that amp...but this was the worst ground noise I've ever had. Pissed off, I unplugged the pedal and the noise dropped back to normal (pedal was on what I thought was a different circuit). I went through and unplugged every wall wart/switch psu on the circuit (ran through like 4 rooms) and turned on the light...hum free. Grounding issues, but my plugs check out right with the tester.

Later, I was messing with two different PSUs (the one above too) and once I joined them to a common ground (the signal jacks), the less noisy psu fixed the noise. This was direct in. Same problem once I turned on my amp.

I know there has to be a broken ground some where now (the house is 85 years old...who knows?....I've ripped so many hidden boxes out of the house)...but I also accept that there is that mysterious "floating neutral" or whatever most likely at the street.

Glowing lights and all that stuff is a good indication.

Anyway, a while back I read about people that use ac/DC/ac converter boxes to clean their power for sensitive devices...supposedly it works, but is expensive.

If your MIG is like my MIG (I know the 50 and 100h are different amps), I wouldn't judge noise floor by that thing at all. Mine sounded different and hissed different in every damn outlet ever. It was really really influenced by grounding and different power. Significantly more than my sunn sorado. Haha.

Good stuff here as well! I hadn't even thought about the outside element of power lines being worked on. They have been doing a ton of that shit in my are. I bet that's it!

[crochambeau]

Nothing is rattling at all.

Good.

How do I tell the frequencies??

[youtube]http://www.youtube.com/watch?v=E_Sf7rSOU78[/youtube]

[youtube]http://www.youtube.com/watch?v=pC4Uzt0qm2E[/youtube]

Often times that second one will ring/buzz a little, because by the time it's passed through your rectifier it's no longer a sine wave.

When you say over unders, do you mean the outlets? Like the way they are outlets are? I noticed this house has a bit of both, which isn't standard now. So weird.

No, the outlet position is really just a matter of taste. I meant over voltage spikes and under voltage brown out dips. Another quiet indicator is needing to change your incandescent light bulbs a lot.

I can't help it. It's my OCD. Sigh.

Just rest well in the knowledge that either position of the outlet is a-okay, and put some fucking cover on your ears when shooting!

My money is on a new cab doing the EXACT SAME THING as your old cabs, which are probably in fine shape if they work well while playing. So.... don't waste your money, unless you really want to.