Could you repost the schematic???
Who Posted a RFI Reduction Circuit for a Marshall Amp a Whike Back???
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Amp Mad Scientist
Ambassador of Heresy
Do you hear an actual radio station playing through the amp?
Or is it:
buzz and hum or hiss?
Many people confuse RFI (radio Frequency Interference) with buzz hum or hiss.
Although actually buzz hum hiss is not RFI at all.
Most of this buzz hum noise comes from the filament circuit of the amp.
And there is a way to deal with that. But it's not RFI either.
Hiss noise is another cause but it's not RFI either.
Most Hum Buzz is EMI, or electromagnetic interference. But it is not RFI.
And so first you need to specify exactly what noise you are experiencing.
Radio Station? Music Voice etc?
Or other?
Last edited:
OP
We have a 50,000 watt FM transmitter 1 5 miles from our house. Some amps play that station loudly...
Amp Mad Scientist
Ambassador of Heresy
If you hear the radio station audio in the amp:
A. It picks up the radio station audio even when the guitar is unplugged, and all effects unplugged?
(turn up the volume on the amp and listen test for it)
Yes or No?
B. You need to listen and confirm the radio station frequency.
Every top of the hour, the station is required to give frequency call letter identification.
Confirm the frequency listening with an FM radio. Note this frequency.
Knowing the frequency that is causing the interference - can be very helpful...
You will choose RFI suppression based on frequency.
C. The most effective RFI suppression is with chokes and beads.
The power cable (for example) might be wrapped around a RFI suppression core....
RFI/EMI Solutions - Palomar Engineers®
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RFI Tutorial Center - Palomar Engineers®
The Radio Frequency Interference (RFI) Tutorial Center contains educational material about RFI – its Sources, Paths, and Victims and associated suppression techniques for general use and specific device/systems solutions (RFI kits). RFI Tutorials RFI Presentations (PDF, Power point, ODP Slide...
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Speaker Presentations - Palomar Engineers®
Bob Brehm – AK6R,” The RFI and Antenna Guy” Bob Brehm is COO / Chief Engineer of Palomar Engineers, with over 60 years of amateur radio experience in contesting, RTTY/digital modes, amplitude modulation, vintage radio restoration, linear amplifiers, and innovative antenna design. Bob is...
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OP
95.1 KFrog
OP
Amp Mad Scientist
Ambassador of Heresy
OP
If you hear the radio station audio in the amp:
A. It picks up the radio station audio even when the guitar is unplugged, and all effects unplugged?
(turn up the volume on the amp and listen test for it)
Yes or No?
B. You need to listen and confirm the radio station frequency.
Every top of the hour, the station is required to give frequency call letter identification.
Confirm the frequency listening with an FM radio. Note this frequency.
Knowing the frequency that is causing the interference - can be very helpful...
You will choose RFI suppression based on frequency.
C. The most effective RFI suppression is with chokes and beads.
The power cable (for example) might be wrapped around a RFI suppression core....
RFI/EMI Solutions - Palomar Engineers®
RFI Tutorial Center - Palomar Engineers®
The Radio Frequency Interference (RFI) Tutorial Center contains educational material about RFI – its Sources, Paths, and Victims and associated suppression techniques for general use and specific device/systems solutions (RFI kits). RFI Tutorials RFI Presentations (PDF, Power point, ODP Slide...
Speaker Presentations - Palomar Engineers®
Bob Brehm – AK6R,” The RFI and Antenna Guy” Bob Brehm is COO / Chief Engineer of Palomar Engineers, with over 60 years of amateur radio experience in contesting, RTTY/digital modes, amplitude modulation, vintage radio restoration, linear amplifiers, and innovative antenna design. Bob is...
I posted a video where you can hear thr station I.D.clearly.
Amp Mad Scientist
Ambassador of Heresy
Home Page
This is the description that will show in search engines for this page.
www.microwavefilter.com
Amp Mad Scientist
Ambassador of Heresy
If you plug in a power conditioner, do you still get the noise?
I am guessing yes...
What you can do is wrap the power cable around a torridial filter ring...
And the filter is going to be selected for 95.1 Mhz...
Amp Mad Scientist
Ambassador of Heresy
Audio System RFI (PA, Studio, Audiophile) - RFI/EMI Solutions - Palomar Engineers®
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ivan H
Ambassador of Tubes & Grooves
You could also install an RF/EMI Power Line Filter in place of the stock IEC AC inlet socket, something like this.
These filters are designed to reduce common mode (line to ground) interference (power lines act as antenna). These filters are fully compliant with all applicable regulations, are usually rated for around 6 Amps & can be had for about 5 bucks. Hope this helps. Cheers
These filters are designed to reduce common mode (line to ground) interference (power lines act as antenna). These filters are fully compliant with all applicable regulations, are usually rated for around 6 Amps & can be had for about 5 bucks. Hope this helps. Cheers
OP
Amp Mad Scientist
Ambassador of Heresy
It's probably not enough, and it's probably not the right frequency.
T-Rex
Well-Known Member
I use the clip on grounding washer, (got a few from TubeDepot). Add a .01uF cap to ground from the sleeve tab and radio stations are gone and the tone doesn't change.
Grounding Washer
Grounding Washer
OP
I use the clip on grounding washer, (got a few from TubeDepot). Add a .01uF cap to ground from the sleeve tab and radio stations are gone and the tone doesn't change.
Grounding Washer
Nice work!
OP
Here's the Marshall schematic with RFI circuit shown far left center...
Clockworkmike
Ambassador of STACKS in WV SHACKS
Sorry i missed this post, yep thats the RFI circuit on a Jcm 900 slx 2500 and the one I posted a while back. Why ONLY the 2500 (50w) has this is beyond me but its definitely there and SEEMS to work. The JCM2000 DSL50 i have had some RFI issues a while back from a bad power line that was being fixed by the power company. During that time it would pick up wireless phones and radios and ultimately I used some ferrite magnets to cut the issue out. Since the line was fixed, its been fine without them.
But during that time, the SLX didn't encounter that issue. From that circuit's interference soak? Perhaps!
But during that time, the SLX didn't encounter that issue. From that circuit's interference soak? Perhaps!
syscokid
Ambassador of War & Peace
Thanks, T-Rex. This is probably the best and least obtrusive solution to Robert's situation!I use the clip on grounding washer, (got a few from TubeDepot). Add a .01uF cap to ground from the sleeve tab and radio stations are gone and the tone doesn't change.
Grounding Washer
OP
Thanks to all who posted!!!