Mass Noise in the amp conected to a battery/inverter
 

Hi there,

I have started busking in Madrid. I have an amp AER Compact 60 IV Slope connected to an Inverter MSW-CPI-300PSL. The inverter connected to a Tracer battery 12V 22Ah.

When I plug the guitar the amp produces a loud noise (I think it is called Mass Noise).

If I connect the amp to a wire at home there is no noise, so the problem might be at the inverter or the battery.

What do you think? Any idea how to solve this problem?

Thanks a lot!!!

Presumably the inverter is defective or the amp requires a PSW (pure sine wave) inverter to operate correctly.

It is unlikely the amp really needs PSW and more likely the inverter has a problem.

Agree with Jon,

Here is a picture of an AER alpha:
http://2.bp.blogspot.com/-x18J2UjIoO...%CE%B11261.jpg

When you see a big transformer like that (the big donuts on the back left), you know it is a traditional power supply and not a SMPS.

Those will not accomodate Modified Sine Wave (MSW) inverters.

Note that old power supply design are more expansive than SMPS... There is no reason why the AER compact 60 would not have one. (Why would AER save money on the compact 60 and use costly stuff on the alpha?)

Thanks for the answers!!!

Yes, the inverter has a PSW. I have phone a store and they told me to put some filters or antiparasitics in the power cable. (it is called "Antiparásitos" in Spanish). I don´t like the idea of modifying the original cable of the amp.

So you think the Inverter might have a problem?

When you plug in to the 220 VAC outlet in Madrid is your amp grounded? I don't recall from my travels there (tourist, not gigging) if your grid is grounded. Many noise issues come from a bad or missing ground.

I play a different amp (Carvin AG300) through an ungrounded 200 W pure since wave inverter. I'm in the US where we use a 110 VAC grounded system.

But I suggest you try grounding the amp chassis and see if that helps at all.

If with grounded you mean if there is noise, the answer is no. There is no noise if I plug into the VAC 220 in Madrid. There is only noise when I plug it with the inverter/battery.

Do you think it will an easy solution for an amp technician?

Thanks so much!

How do you feel about the prospect of busking chained to a cold water pipe? That might solve your issue. :)

What type of pickup are you using?

An experiment that might shed some light: with your amp plugged into the inverter running off battery (and you hearing the noise), plug some other input or output of your amp into some other piece of equipment that is grounded to earth with a 3-prong AC mains connection. If the noise does not significantly reduce or go away altogether, then the problem is most likely that your inverter and your amp are not playing together well.

What about using this?

https://www.thomann.de/es/bss_ar133.htm

I am using a Taylor - 314ce V-Class. I have tried also with my baby Taylor which has lg baggs pickups and there is also the noise.
I have also tried my amp fender deluxe and the same...

This type of situation is the exact reason I cringe every time I see someone suggest and inverter and battery setup to "save money" instead of using a amp that has built-in battery capabilities.

Hopefully this will be a fairly easy to fix problem, but it doesn't sound like there's a quick n' easy solution.

The circular transformer is called a "toroidal" transformer, based on the doughnut shape known as the toroid. It is the most expensive power transformer used audio gear because of the complexity of the winds. It has strengths and weaknesses. The greatest strength is that it produces a fairly weak physical magnetic field, making it induce less noise into the surrounding circuits and allowing a smaller circuit package. As electronic packages become smaller and lighter this becomes more and more important. However, the weakness of the torroidal transformer is that it can't handle DC offset in the incoming AC well at all. When it is presented DC offset, the toroidal transformer saturates and begins putting out tons of noise.

The more modern EI transformer can handle DC offset but adds size and weight and has to be carefully designed for the application and carefully mounted to have as small a magnetic footprint as a toroidal one. It is a good competitor, but not completely superior to the toroidal one.

So you see, there are competing design issues that require a commitment one way or another.

Bob

No I mean electrical grounding (called "earthing" in the UK). In the US our household AC has a hot (energized) wire, neutral return and separate ground (earth).

The ground is there for safety - if you are using an electrical appliance and there is a failure such that the part you're touching gets energized from the hot supply, the ground is designed to conduct electricity rather than have current flow through your body.

In the US the ground and neutral are bonded (electrically connected) at the home's electrical service panel. The ground (earth) is required to be connected to a metal rod driven into the earth beyond the house's drip line (from the roof). Metal water and gas pipes in the house are required to be bonded to this ground as well.

If an amp is plugged into an outlet with a bad or faulty ground connection this can produce noise, usually a hum.

An inverter is independent of the electrical grid so the ground connection on the inverter's AC outlet doesn't connect to an earth ground. This could be the source of your noise since you posted it was not there when the amp was plugged into an AC outlet but was present when powered from your inverter.

Can you use a jumper wire to connect your inverter's chassis to a solid ground connection (like a metal cold water pipe) and see if that eliminates the noise?

Pardon me for jumping in where the depth is deeper than my understanding. But, an idea popped into my head, based on limited knowledge of the "ground lift" function some devices offer. Would grounding the inverter chassis to the amp chassis work? Certainly would be more convenient if it did.

If the amp has a ground on its power plug (i.e., 3 prong plug in the US) and it plugs into a grounded outlet on the inverter, then the two chassis grounds are connected. But if that ground reference isn't true ground (floating voltage reference susceptible to picking up noise) it won't help any.

True ground = zero voltage potential. Grounding the inverter chassis would do the same thing as grounding the amp provided the amp's power cord has a ground prong. Again, my recollection of European 220 VAC wiring is dim as I never worked there.

Thank you everybody!!!

I have left the amp with a tech. Hope he will solve the problem!!! :-)