hello all,
Recently I moved my system to a friend's place and I hear a lot of RF noise. At my place, the amp is dead quiet. The cases are shielded (and connected to earth) , the cables are shielded, everything's shielded and connected to earth. No humms or anything, just RF noise.
Case is made of stainless steel, interlinks are diy silver/teflon with copper shielding about 2 feet long.
CD player is connected to earth.
I looked at the amp itself and everything is still neatly soldered and in place. Testing with my multimeter gave no errors.
Moved everything back --> quiet again !
I've tried just about everything...
He lives about 200 meters from me so I think it's not the RF signal strength.
Any ideas what's the problem here?😕
edit: typo's
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My GainClone site (updated!)
Recently I moved my system to a friend's place and I hear a lot of RF noise. At my place, the amp is dead quiet. The cases are shielded (and connected to earth) , the cables are shielded, everything's shielded and connected to earth. No humms or anything, just RF noise.
Case is made of stainless steel, interlinks are diy silver/teflon with copper shielding about 2 feet long.
CD player is connected to earth.
I looked at the amp itself and everything is still neatly soldered and in place. Testing with my multimeter gave no errors.
Moved everything back --> quiet again !
I've tried just about everything...
He lives about 200 meters from me so I think it's not the RF signal strength.
Any ideas what's the problem here?😕
edit: typo's
---
My GainClone site (updated!)
there are a few ways, mostly withinput and output filters, and gain limiting. basically, you can add a cap and a resistor in parallel with the feedback resistor to get a lower gain at a high frequency. also, a small inductor in parallel with a 10ohm resistor can be used, this will increase the impedance seen at RF.
an RC network can be used on the input. also, national lists using a 100nF cap across the inverting and non-inverting leads as a way to improve preformance in areas with florescent lighting and RF problems.
an RC network can be used on the input. also, national lists using a 100nF cap across the inverting and non-inverting leads as a way to improve preformance in areas with florescent lighting and RF problems.
matjans said:
How do you know it's RF. How does it sound? What do you hear?
Can you be a bit more descriptive, please.
Greg
details
purplepeople: yes, earth is grounded 😉
Nuuk: with a separate wire to separate ground, not connected to star ground. wire goes to wall socket.
Greg: I can hear (and even understand) a dutch radio station. Somewhat distorted but that's it.
Removing all interlinks and cables makes it less annoying but only a little.
edit: typo's
purplepeople: yes, earth is grounded 😉
Nuuk: with a separate wire to separate ground, not connected to star ground. wire goes to wall socket.
Greg: I can hear (and even understand) a dutch radio station. Somewhat distorted but that's it.
Removing all interlinks and cables makes it less annoying but only a little.
edit: typo's
What about removing the speaker cables? 🙂 Or at least using something very short. It's quite possible they're acting as aerial.
Try connecting the case to the power star ground point via a 100R resisitor which is bypassed by a 0.22uF capacitor.
Re: nuuk
NuuK: ahh, that helps. Just tried it an almost all noise is gone. Strange but it works. A little bit remains.
No worries, i'm moving it back to my place anyways.
NuuK: ahh, that helps. Just tried it an almost all noise is gone. Strange but it works. A little bit remains.
No worries, i'm moving it back to my place anyways.
nuuk: almost,. I made my cases out of storage boxes. The lid was plastic so I coated that with 2 layers of aluminium tape and connected that to the rest of the case. Tested it with a multimeter: no resistance.
But the strange thing is I don't hear anything in my room and (before the mod) i just heared a radio station in my friends room, although we're just 200m apart.
As i intend to use it in my room there;s no problem. 🙂
But the strange thing is I don't hear anything in my room and (before the mod) i just heared a radio station in my friends room, although we're just 200m apart.
As i intend to use it in my room there;s no problem. 🙂
It could well be local RF interference. How many times have you had a bad radio signal at a red light, moved your car 1m, and it clears up?
I may have to revisit RF suppression on my amps. Usually they sound great, but my neighbor is a major HAM buff and I suspect he is behind the rare occasions when I get some noise at the outputs.
I know this doesn't apply to you, matjans, because the outside of your amp is nonconductive. But for others, connecting to safety earth that way is dangerous. Mr. Pass seems to like thermistors for that purpose, and Rod Elliot has had success bypassing with diodes.
I may have to revisit RF suppression on my amps. Usually they sound great, but my neighbor is a major HAM buff and I suspect he is behind the rare occasions when I get some noise at the outputs.
I know this doesn't apply to you, matjans, because the outside of your amp is nonconductive. But for others, connecting to safety earth that way is dangerous. Mr. Pass seems to like thermistors for that purpose, and Rod Elliot has had success bypassing with diodes.
cap across input
A small cap of 220-330 Pf across the inputs will get rid of RF noise. It did for me anyway.
Greg
A small cap of 220-330 Pf across the inputs will get rid of RF noise. It did for me anyway.
Greg
in my case - i can hear FM 93,7Mhz station .... my GC it is Tube buffered GC . with LPF on input so it`s strange to me. and it isn`t
caused by the tube (i`ve checked this - 🙂 ) with hum reduced to (nearly) zero and many "experiments" i have still "radio GC" .......
for now i know that the power (and/or ground) wire from transformer "works" as antenna....... maybe i`m right , maybe not... ???? who knows ?
99 times out of 100, interference suspected of ham radio operators can be traced to deficiencies in the design in audio equipment, telephones, televisions etc. on the other end. and it's pretty easy to "id" ham interference since we are required by law to identify our stations. if you suspect ham interference just drop the guy a note, the FCC has serious standards they impose on station operation and the ARRL has local engineers and volunteers who can help the operator out, or can help you with your interference problem.tiroth said:
particularly notorious in respect of RFI are inexpensive cordless telephones manufactured in China -- they will come with the appropriate FCC design approval sticker which has been completely faked. they radiate out-of-band interference like crazy -- this was a big problem about 5 years ago.
there are a generation of police and emergency services transponders in the U.S. with a software design flaw -- this was mentioned in one of the ham bulletins I received a few weeks ago -- so even well intentioned manufacturers come up with bugs that require fixes.
I didn't mean to imply that my neighbor was doing anything untoward. I just figure that when there are literally half a dozen sizable attennae next door that there is some RF being generated at times. 😉
Since a minimal GC is basically a wideband amplifier ^_^ it is certainly a problem to fix on my end.
Since a minimal GC is basically a wideband amplifier ^_^ it is certainly a problem to fix on my end.
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