@#$%#$ radio stations coming through my amp!

[Clpether]

I had a rehearsal with my 2204 yesterday and it sounded great only one problem It was picking up some Asian radio station that was just as loud as the amp. I've picked up stations before but not this bad. Is there a fix to this anyone knows of (like I need to get this amped serviced).
Cheers!

 

[bste328]

start by changing preamp tubes. Maybe someone has started being microphonic!

 

[Gsxrbusa]

Some good info in here. viewtopic.php?f=3&t=78003

Specifically Mike Fortin's response.

 

[Clpether]

Yup! That is some good info. I will try the tubes first if not I will take mikes advise. After all he was the one who modded my amp! Thanks guys!

 

[FortinAmps]

Yup! That is some good info. I will try the tubes first if not I will take mikes advise. After all he was the one who modded my amp! Thanks guys!

Hey Clay,
I added that RF cap to your amp. I'm betting that you are located very close to a transmitting tower. Give me a call at work today or hit me on my email, I might be able to help out a bit more.
Cheers,
Mike
mike at fortinamps dot com

 

[rockstah]

Mike, curious, what value grid resistor is on the input stage?
Mark

 

[Clpether]

Thanks Mike and will do! I should mention this happens at our rehearsal spot in Cherry Beach which is near lake shore. It's a very industrial area and I am betting that you're right on the transmission towers!

 

[FortinAmps]

Thanks Mike and will do! I should mention this happens at our rehearsal spot in Cherry Beach which is near lake shore. It's a very industrial area and I am betting that you're right on the transmission towers!

No problem, yeah, looks like there is a few in the cherry beach area. http://maps.google.ca/maps?hl=en&tab=ll then type in " Radio Stations & Broadcasting Companies near cherry beach toronto"

Mike, curious, what value grid resistor is on the input stage?
Mark

Hey Mark,
Generally a .01uf will work fine from the ground lug of your input jack to the closest chassis point. Sometimes I'll solder the other leg to a pot casing.
Cheers,
Mike

 

[rockstah]

Hey Mike, interesting stuff.
Mark

 

[protoplasma]

It seems the tried and true 68k grid stopper on the input stage works in all cases that I've had issues with. The problem of course is the added thermal noise, AKA, hissssssss.

 

[rockstah]

It seems the tried and true 68k grid stopper on the input stage works in all cases that I've had issues with. The problem of course is the added thermal noise, AKA, hissssssss.

thats what im thinking. i guess the need for a lower value there is something he prefers.
Mark

 

[FortinAmps]

It seems the tried and true 68k grid stopper on the input stage works in all cases that I've had issues with. The problem of course is the added thermal noise, AKA, hissssssss.

thats what im thinking. i guess the need for a lower value there is something he prefers.
Mark

When the RF rides on the ground casing on your input cable, the 68k or whatever input grid resistor isn't going to be enough. In addition to the input grid resistor, a cap is needed to give the RF a path to ground.

Cheers,
Mike

 

[Soundguy213]

wrap your head in aluminum foil and plug in through the foil =)

 

[FortinAmps]

wrap your head in aluminum foil and plug in through the foil =)

 

[sinfish]

Try all the simple stuff first. Try new instrument cords, Try a different Wall outlet, Do you pedalboard or something in your effects loop that requires wall power? If yes is it plugged into a different outlet than the amp causing a loop?

 

[threadkiller]

..... Asian radio station ....Cheers!

It's the Chinese preamp tubes

 

[FortinAmps]

 

[sinfish]

 

[charveldan]

You want this mod...............


http://www.ryansguitars.com/2008/05/rf- ... baron.html


It's easy and it works, did it to both my JMP's.

 

[duesentrieb]

Generally a .01uf will work fine from the ground lug of your input jack to the closest chassis point. Sometimes I'll solder the other leg to a pot casing.
Cheers,
Mike

+1 same here.

Hi Mike btw