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How can I stop my guitar amplifier from getting severe radio interfearance? Answered

I have a Peavy Vypyr 15 watt combo modeling guitar amplifier. It has severe radio interfearance and picks a spanish radio staion up and is ver clearly and loudly heard through the amp. I need this amp because without it the other two amps cant get as distorted, as loud, as clear, and they cant pickp the midrange that the vypyr puts out.
Is there any way I can sheild, or block it from doing this?

the second picture shows the exact diagram of the splitter involved in the setup


Couple of questions for you...

If you unplug your signal cords and just plug straight into 1 amp at a time, is there any hint of the radio station?

Are you running from one effects loop or output of an amp into another in order to increase the gain/distortion?

Inside your homemade splitter, is it shielded/in a complete metal box with the grounds all tied together or at least the jacks grounded to the box?


It could be a number of things, but radio interference normally comes from poor shielding leading up to and including the high gain area of the amp. You can help by making sure your cables are in good condition - no breaks in the cords. You can fix broken cable ends by cleaning up any frayed wires and resoldering them. Make sure any areas in the signal path are well shielded. Also, try to angle the cabinets/amps so that they are not all parallel as shown in the picture. Angling them will help reduce the additive effect of the transformers flux lines to each other.

Of course, if you live near that station, it could just be overpowering your amp and there isn't much you can do about that.

Get back and we'll see what more you can troubleshoot.


the radio station is somewhat heard but is so faint its unaudible

there are no further effects on my sytem such as pedals

the gronds for the jacks are soldered together but thats it its also in a plastic unsheilded case

the cables (the ones in which I can remove the sleve over them) seem to be in just fine condition and dont have any physical defects. The cable I use for the main input has rubber over it and cannot be removed therefore it could very well be damaged but I would not know of it

the amps are on a stand in which one of them is tilted at a 45 degree angle (the vypyr iss tilted) the other two i cannnot tilt because there is no more room on the stand that permits that.

I think most of your problem is in the splitter. Follow Gmoon's advice and try again.

I still think you should shield the splitter box and use the shield for ground/throughput. That way, your signal wires in the splitter are shielded including the jacks.


It could create a very small loop, but if you line the whole interior of the box with foil or copper tape, or whatever metal you choose (clamping the edges of the jack holes with the metal and the jack bases) , it really won't hurt it as the ground all ends up at the same places inside. What it will do is create a Faraday cage (shield) around the signal wires, keeping outside signals from impressing themselves on them.

You do realize that the LED's are diodes... special ones, but still diodes. What is the main detector of AM radio? A diode. So, you have AM detectors connected to your gain stages and you are also impressing a voltage/current loop through them and the common grounds of the amps, etc. If you remove the battery (to open the circuit) does the radio station go away or reduce? If so, try removing the LED's and test again. I bet it will be solved.


As gmoon and you have realized the soure of the radio signals is in fact the splitter. With the LED circuit open not only is there no radio interfearance but my internal guitar sheilding is having auditorial effects for the beter as well. The tone(especally in the lower range) is significantly brighter, there is no interfearance, no hum (that is as loud as before and almost nonexistant) so therefore you guessed it right, I have built an AM radio. I will definatly remove the LEDs and use them later as well as sheild the interior of the splitter, very similar to the way I did with my guitar

That's why I wanted you to shield the box, to prevent the wires/component leads inside from being able to act like antennae. The shielding will prevent the RF from entering the box.

Still, Gmoon's suggestion of an active splitter is better than the passive version IF you want light up indicators. Probably a TL082 per line, 1/2 as the buffer amp and the other 1/2 to drive the LED, thereby keeping the LED's separate from the signal lines. Use the ground "switching" you used originally to turn them on, PCB mount everything inside a metal box and you should be good to go.

Glad you can fix it now.



7 years ago

It sounds like your splitter is the problem. Is it active or passive?

If passive, you may need resistors in series with each input to prevent any interaction. You also may have a ground-loop issue.

It would be simpler to make a passive a/b/c switch rather than an a/b/c/y splitter--If you can be satisfied with each amp individually, rather than all three at once...

Post the splitter schematic, and maybe we can help.

passive however I hope to make an active one soon

ground loop?

I will definatly post it

Id prefer all at once however individualy could become accepible

There are several things you can check:

-- Try inserting a boost or buffer before the splitter. Guitars have a medium to high output impedance (5K to 15K approx), and that might help drive the amps and lower the noise.

-- Poke around and adjust the wiring dress. Tighten the jacks in the chassis. Look for cold solder joints.

-- Make or buy an active splitter. Because the splitter is passive, you're connecting all the amplifier inputs together in parallel. That can lead to unwanted side effects with one or more of the amps.

-- Remove the LEDs, they are kind of redundant (it's pretty easy to see if a plug is inserted, so why use an indicator light?) They form possible loops, and if any are multicolor, they can REALLY introduce a lot of noise...

-- Add a capacitive "shunt" somewhere in the splitter, between the signal and the GND...something between 50 and 500 pF (that's PICO farads). This should bleed off any really high frequencies.

-- If nothing else works, look for Ground Loops. One type of ground loop is simple: having grounding metal jacks AND wiring the ground tabs on them as well (two ground paths at every jack). Modern amps almost always use plastic-body jacks.

Try removing the GND connection on one or more of the output jacks. How can that work? If all the amps have correctly earth-grounded chassis, then you don't need more than one ground pathway to the guitar. They already share a ground.

If you try this BE VERY CAREFUL. You MUST always have earth grounds to each amp (third prong on the power cord) AND a connection to earth ground for the guitar (through the guitar cord). It's a safety issue. But they don't need multiple ground paths.

Like a rough signal booster circuit?

I have resoldered everything in side and though it did lower the noise factor it did not stop it compleatly

the passive circuit is really nice for when I put an effect on the Vypyr, it will play somewhat through the other amps however if the passive circuit is the source I will remove it

the LEDs were there for two purposes only, to ensure each amp is getting signal and to make it look nicer, therefore they can very easily be removed

would adding this cappacitor be something like a tone knob on "10"?

it is not seen by the picture but both the vypyr and the Ibanez amp have a metal jack. the Ibanez jack was replaced with the metal jack because it broke off and was pulled off of the motherboard inside. I dont beleave there are any ground loops because the GND tab of each jack is the only contact touching other GND tabs

should I have an earth ground directly added to the input signal chord?

on the Ibanez amp the power input chord plug has been replaced. The GND prong broke off and I replaced the plag with a much heavy duty plug than the stock. I am confident that the wireing in the plug is correct but I dont know if this would cause any problems as far as sound goes

Ive noticed that the radio signals are only heard some of the time, the signals come in at random it seems

This kind of pickup happens because the input sensitivity of the amp is very high, and it has a high input impedance. Connecting a nice antenna guitar cord to it, and you have a radio stage.

The simplest fix is to get some clamp on cable RF screens from Radio Shack, or perhaps steal one off a dead laptop power cable.


what do you mean by The simplest fix is to get some clamp on cable RF screens from Radio Shack, or perhaps steal one off a dead laptop power cable.?

thats a good point about the impedance. the Vypyr amp has a 4ohm amp that runs a 3ohm speaker (this was not my doing, the amp actually came like this but I never could understand it)

. Make sure you have a good ground. Make sure your cables are shielded and/or twisted pairs.

I have setup that uses a 4 way homeade splitter, when the vypyr is turned off but the other two on, there is very minimal interfearacne and most of the time its so faint that it is unheard and can only be heard at very high volumes, however twhen the vypyr is on the rest of the amps ick it up too. they are all pluged into a surge protector and then into the wall. so my groud is good and the cables arnt the problem so what could it be?