My Hartke LH1000 suddenly started picking up a local radio station signal. This happens with or without the instrument cable plugged in. And I’m not using a wireless system. Any idea why?
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Amp picking up radio station
- Thread starter frankneill
- Start date
Has it been moved recently? Still plugged in to the same outlet? Or a different outlet? Are you using a multi outlet strip? Pedals? Worst case is a filter cap somewhere in the amp has gone bad. Best case is it's something simple, but complicated to troubleshoot. More info might help. Sorry, that's all I've got from this end...
Hopefully it's a good radio station. If that WAP song is coming through my amp I might just destroy it Ritchie Blackmore style.
Try a different outlet. If it keeps happening, may be worth getting a power condition or ferrite ring to put on the power cable.
- Feb 12, 2006
- 60,951
- 5
- 220,593
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Very unlikely to be a bad filter cap, the odds are worse than Vegas.
I would verify that the power receptacle is actually (as in really) grounded and that the ground pin on the plug is intact first.
I would verify that the power receptacle is actually (as in really) grounded and that the ground pin on the plug is intact first.
If nothing else has changed at your end....If the radio station is local, contact the station’s engineering department and ask for assistance. They may have a solution. They may have been tuning their antenna and created the problem that they aren’t aware of. They usually take complaints very seriously, if they don’t file a complaint with the FCC.
@Aged Horse, I was told many years ago that the problem was between the input jack and it’s first landing point inside the amp, and it could be helped with RF shielding. Any truth to that?
Some amps have an insulated 1/4" input jack. The idea is so the jack does not ground out on the front panel so star grounding can be used (I.E. only one centralized ground is used to prevent ground loops). A very small capacitor is often used between the sleeve of the jack and the front panel (chassis ground) to drain away RF.
One of my amps was picking up Rush Limbaugh. I believe the RF was entering the signal path on the first tube, because if I pulled V1 the problem was eliminated. However I got the impression there were lots of factors contributing to the problem.
The signal tended to fade in and out depending on time of day. The problem tended to get worse towards the evening. If I disabled the ground on the AC plug, the radio signal was eliminated and the amp had less hum...but of course that is not a safe solution.
The amp has a 10ohm resistor offsetting the signal ground from the chassis. The resistor is good and the connections are clean and secure. I also checked the RF drain capacitor on the input jack; it was good.
Removing the top panel also seemed to reduce the strength of the radio signal and reduce hum. Everywhere there is a screw on the top panel has been filed, so there is metal to metal contact between the chassis and panel. It's interesting to hear how the noise changed as I loosened or tightened various screws in the top panel. So ground micro currents through the amp's chassis seem to be relevant.
I also noticed proximity of my hand to parts of the tone control circuit, which is between V1a and V1b had an impact on the noise. So it's possible the noise was picked up later in the amp.
Eventually I rolled tubes through the amp. This did not change the symptoms, but after I adjusted the balance of the Phase Inverter (PI) it seemed to reduce the hum quite a bit and the radio signal appears to be gone...knock on wood
. Perhaps the signal was being introduced into the front end of the preamp, but not being rectified until the PI (V2b). Honestly, I can't say for sure. I just hope the problem does not return.
I have had a similar problem using certain combinations of effects pedals with some of my amps, so I think to root cause is probably the electrical system in my house. The amp picked up radio on various plugs in my house, but when I took it to work, it it did not pick up the channel. However, I checked the amp in the middle of the day at work, and often I did not hear a radio station at my house in the middle of the day. As you might imagine, this type of problem could be very difficult for a tech to track down since the amp would probably not pickup the radio in the shop
.
- Feb 12, 2006
- 60,951
- 5
- 220,593
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Possibly, if the ground current steering is no longer how the designer intended. That would also be RF rejection rather than shielding.
Well, Nigel, throw down your axe and stomp off stage.
I live very close to the local towers - can't get away from it, although for some reason some bass/amp/cable combos are worse than others ...
The nice ol' neighbor next door claimed my bass was coming through her easy listening station. I think I was just playing really loud.
Hah!, my first amp was a small used guitar amp that did this. I was living in Vancouver at the time and it was picking up a Chinese language radio station 
. Very annoying.
. Very annoying.
Have you checked for a loose nut behind the bass?
Maybe try an SVT head and an 8X10 and a retro T-bird and a coiled cable. That will be awesome and you'll forget all about the radio thing.
Maybe try an SVT head and an 8X10 and a retro T-bird and a coiled cable. That will be awesome and you'll forget all about the radio thing.
The loose but behind the bass is usually the guy playing it
(runs for cover, laughing)
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Let us know if it starts to pick up WKRP in Cincinnati. If that that happens, it may also involve a tear in the time/space continuum.
I recall a while back somebody started picking up radio on their rig and it turned out to be a bad diode in a pedal acting like a crystal radio.
This was something that used to happen often way back in the day.
I remember not only radio stations, but the occasional pilot or train communications and even cop radios suddenly blaring out at gigs.
I just figured it was something the amp manufacturers had overcome since I hadn't heard it in a loooong time.
Guess not.
I remember not only radio stations, but the occasional pilot or train communications and even cop radios suddenly blaring out at gigs.
I just figured it was something the amp manufacturers had overcome since I hadn't heard it in a loooong time.
Guess not.
