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Chip Amps Amplifiers based on integrated circuits

GC as Radio...?
GC as Radio...?
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Old 13th August 2003, 02:54 PM   #1
sa_schulz is offline sa_schulz  United States
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Join Date: Aug 2003
Location: Lexington
Default GC as Radio...?

Since my last post, I found a ground not being grounded. All is sorta well. It plays music in ways I did not know existed. My circuit is a inverted Loesch. I find to my dismay that my GC picks up a strong local FM radio station. This leads to superimposition of the music with radio. This is annoying mostly at low level listening. Higher levels sorta mask the radio. I just got back from a trip to my parents house and played GC there ( rural tennessee ). No radio signal in two very different places. Absolutely dead quite at all volumes. I get back here (downtown Lexington KY) and get radio again. It does not get louder with volume increases. Sometimes ramping the volume pot without input, causes the radio signal to go away for awhile. It just fades away. I wonder if it is getting into PS rails? I have not tried the 0.1uF bypass caps yet.

Any wisdom?,


P.S. Anybody in the Lex area building GC's, HiFi etc.?
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Old 13th August 2003, 03:42 PM   #2
phase_accurate is offline phase_accurate
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Join Date: May 2002
Location: Switzerland
One thing that sounds quite weird to me is the thing with the pot: This sounds almost as if you had an intrinsic cristal detector, like grandpa used to have some decades ago !


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Old 13th August 2003, 03:53 PM   #3
JOE DIRTŪ is offline JOE DIRTŪ  Canada
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Location: Brantford, ON
what type of case do you have? and is the amp isolated from the case?
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Old 13th August 2003, 04:39 PM   #4
roncla is offline roncla  United States
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Join Date: Aug 2003
Location: texas
You need to ground the case(if its metal) . All i make is wooden cases and i have to copper line them and ground to eliminate RF signals.
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Old 13th August 2003, 06:10 PM   #5
sa_schulz is offline sa_schulz  United States
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Join Date: Aug 2003
Location: Lexington
Default metal enclosure

I have the PS in a plastic Radioshack project box roughly 5"x4"x9" with both trans and rectifier mounted on the metal lid/plate. The GC is in a metal enclosure a la shigaraki (upright even ). It is the kind with two halves that interlock. The chip is the TF isolated package. The heatsink is a commercial one normally for something like 2N3055. I drilled holes for the lm's and grounded the sink to case. All leads short and direct etc. The only things I didnt do was the 0.1uF bypass and the 1uF between the pins 1,4.

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Old 14th August 2003, 03:45 AM   #6
Sawzall is offline Sawzall
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Join Date: Jun 2001
Location: Alexandria, VA USA
The volume of the radio does not go up *or* down? That makes it real wierd to me. If you lived close to a transmitter, its possible that you could create the magic tuned LC combination by accident - but it should go up an down in volume.

UNLESS, the signal is coming in on the speaker wires or something?
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