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Old 14th February 2013, 05:43 AM   #3951
shaan is offline shaan  India
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Let me share this interesting phenomena that's common to the CFB amps I build.

Whenever I touch the input pin while wearing my slippers the amp comes alive and a lot of AM stations can be "tuned" just by varying my grip on the input pin. The signal is quiet clear and has better fidelity than commercial AM tuners. The show stops if I touch the floor or the input ground. Funny anomaly.
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Old 14th February 2013, 06:49 AM   #3952
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Quote:
Originally Posted by shaan View Post
Let me share this interesting phenomena that's common to the CFB amps I build.

Whenever I touch the input pin while wearing my slippers the amp comes alive and a lot of AM stations can be "tuned" just by varying my grip on the input pin. The signal is quiet clear and has better fidelity than commercial AM tuners. The show stops if I touch the floor or the input ground. Funny anomaly.
Shaan,

you must have a long aerial
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Old 14th February 2013, 07:06 AM   #3953
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good afternoon mr.shann, mr.LC.saya want to assemble a klass amp ssa that, I read the article from the power amp bonsai if no one power amp pack assembly results bonsai nx and sx type .... I've assemble and mr.nafiri ssa power amps ... melodious voice, pleasing to the ear and pain in telinga.apakah mr.shaan, lc is assembling a klass amp?
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Old 14th February 2013, 08:11 AM   #3954
shaan is offline shaan  India
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Shaan,

you must have a long aerial
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Old 14th February 2013, 08:35 AM   #3955
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Originally Posted by Nico Ras View Post
you must have a long aerial
And special audiophile slippers.
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Old 14th February 2013, 11:32 AM   #3956
PauloPT is online now PauloPT  Portugal
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Seems that now the oscillations are under control.

I soldered another 100 ohms at the gate of the mosfets (they're wired, not soldered directely to the board for now) and twisted the PSU cables.
The input cable is of very bad quality. It's not shielded and has been bitten and chewed many times by my cat. It's been soldered that many times after the bites. My cat bites every cable he can find.
The filter capacitor is at 330pF now with the 1K paralleled resitor to ground. Why did you choose only 20pF?
I still ear some noises from the radio but now it's not a whistle, it's noise. When I connect the input cable the noise increases. Is this an oscillation too or it's normal?

Thank you again for your help guys.
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Old 14th February 2013, 02:11 PM   #3957
PauloPT is online now PauloPT  Portugal
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Quote:
The filter capacitor is at 330pF now with the 1K paralleled resitor to ground.
Sorry about that. What I meant is:
The 1K resitor is in series with the input. The 330pF cap goes to ground and it's paralleled with a 10K resistor. Now it's good
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Old 14th February 2013, 03:35 PM   #3958
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Quote:
Originally Posted by shaan View Post
Let me share this interesting phenomena that's common to the CFB amps I build.

Whenever I touch the input pin while wearing my slippers the amp comes alive and a lot of AM stations can be "tuned" just by varying my grip on the input pin. The signal is quiet clear and has better fidelity than commercial AM tuners. The show stops if I touch the floor or the input ground. Funny anomaly.
This is why I use an RC snubber across the input. Ideally the input would be buffered so this wouldn't happen. Just like an amplifier may anomalously oscillate into specific loades, it may also oscillate with specific sources. Oscillation may cause DC offset or otherwise destroy the speakers.
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Old 15th February 2013, 01:56 AM   #3959
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Sorry about that. What I meant is:
The 1K resitor is in series with the input. The 330pF cap goes to ground and it's paralleled with a 10K resistor. Now it's good
This had been said to you previously.
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Old 15th February 2013, 09:05 AM   #3960
PauloPT is online now PauloPT  Portugal
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Quote:
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This had been said to you previously.
I was just correcting my previous post because it sounded like I had a 1k resistor paralleled with 330pF. It was too late for editing. What "sounds good" is not the amplifier (wich now sounds good but for other reasons) but my post.
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