AC filtering?

[toocool]

Is there any options to filter the AMP's electrical system?

[antonis]

It depends on what you mean by "filtering", but yes, there are..

A commercially availiabe transient suppressor followed by an - also commercially availiable - AC line filter (some combination of LC filters) and a series combination of 100R resistor & 100nF cap across the transformer primary (to prevent large inductive transient at turn-off) should be enough.. 

[GibsonGM]

I would as "why" do you need to filter your AC power?   Most amplifiers (all?) will have power filtering built-in.   If there is noise, hiss and so on, it can mean something inside your amp needs to be repaired.   Like filter caps, which dry out over years.

Can you elaborate?

[amptramp]

You can get AC line filters with a ground connection or not (the latter for medical equipment where they don't want bad grounding to bring your ECG electrodes to half of AC line voltage).  If you have a ground pin on your amp, use the grounded ones and make sure you use a circuit tester to make sure you have the ground wired in.  If you don't have a ground pin on your amp, add one.  (In fact, build a circuit tester into the amp - you can't lose it that way and it is just three neon lights.)  The tester looks like this:



Adding a varistor voltage clipper/transient suppressor is also a good idea although the zener-type may perform better.

[toocool]

I have a Fender Frontman 212R amp, and It is very noisy.

I thought that my effects are noisy, or my guitar has a problem BUT... I connected a jack into the amp without guitar or effect, just the cable, and i still hear this hum: https://drive.google.com/open?id=0BzeBH5OC4D6yT3FFaXFGSThjbFU

The volume 10, treble 10, bass 10, mid 4.

But you can hear this hum, on lower volume settings. People say, I have dirty power, and I need AC filtering.

[GibsonGM]

Wow, that's not too cool, is it? 

If you do not plug ANYTHING in, at all - does it do this?   

I would not be surprised by a cord NOT connected to anything picking up all kinds of noise. Anything near will be picked up (it is an antenna if not connected to your guitar or pedals!).   Lighting, CFL bulbs, computer power supply - lots of things can create that noise.

So, if it only does that with JUST a cord plugged in, that might not be a problem....you can try plugging a cord in, and place a wire between the 2 'terminals' of the free end...the sleeve and the tip.  Short them together, which simulates "grounded input".     That should make things quiet. 

And the amp SHOULD have a grounded input with NO plug inserted, although some do not 'feature' this. 

All that really matters is - is it ok when you connect your guitar?

[toocool]

When the AMP is on and nothing connected it is quiet, nothing can hear.

When I plug a cable with free end (the cable connected to the AMP but the other end is not connected to anything), It starts humming.

[GibsonGM]

And if you then plug in your guitar, what does it do?

[thermionix]

When the AMP is on and nothing connected it is quiet, nothing can hear.

When I plug a cable with free end (the cable connected to the AMP but the other end is not connected to anything), It starts humming.

That is normal, your amp is not at fault.

[antonis]

Your amp is OK so don't keep searching for AC filtering anymore.. 

If the noise level with no Input connection and with shorted cable (e.g. via aligator clips) is the same, your amp DOES have grounded input jack..