Home » Audio » Group Build » Ground isolated from chassis - now it's an AM radio
now it's an AM radio [message #30890 is a reply to message #30868] Wed, 09 March 2005 04:39 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
On the AM radio, you might find that you can use a small cap to connect what you just isolated( and discovered the RF issue by doing ). Small, as in .01 or .005 uF of ceramic cap. you don't need much voltage rating, so it won't have to be big( like a 6kV .01 uF would be ).

You don't want much connection at audio frequency( else it will conduct the hum that youisolated for in the first place ), but at RF you want a dead short. Ceramic of the proper size can do this for you I think.
regards,
Dogulas



Re: now it's an AM radio [message #30899 is a reply to message #30890] Wed, 09 March 2005 14:08 Go to previous message
Wayne Parham is currently online  Wayne Parham
Messages: 18676
Registered: January 2001
Illuminati (33rd Degree)

Good idea about the small value ceramics. It's amazing how much RF is present on the power line. The AC power lines are a nice long antenna, and the power supply rectifier is a good detector. Electrolytics in the supply filter don't shunt much RF because internal resistance grows too high at high frequencies. Open up the input, and the amp is great for playing the 50kW boomer station in the area.


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