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Old 5th March 2003, 08:31 AM   #1001
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sorry, also had to do this, 1000th post in this thread!
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Old 5th March 2003, 08:35 AM   #1002
Nuuk is offline Nuuk  United Kingdom
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Now go back to bed
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Old 5th March 2003, 09:32 AM   #1003
Bricolo is offline Bricolo  France
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what can put my amp in oscillation?

zeno: I have no scope, and no light bulb
but I used an Ampmeter on the supply rails, and it draws 0.3A at iddle, bot not always

sometimes it's not, and a little input signal during 1/2 second then stop, then it's 0.3A
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Old 5th March 2003, 10:00 AM   #1004
protos is offline protos  Greece
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Well it shouldn't get hot at all with no input and no output.99% it's oscillation accordind to the tradition here.Check all your connections then since it seems you don't have the input pot tie a 50k or so from the inverting input to ground.
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Old 5th March 2003, 10:01 AM   #1005
zeno is offline zeno  Europe
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If I am right, you don't have a pot on the input? (Hence the earpads )

Did you use the original shematic (National datasheet or the 'inverted gainclone') or the reduced Peter D's schematic?

Leaving out components might make the circuit more sensitive to osccillation and instability.

Is it better when you shield the circuit? (You should be able to measure the temp of course)

Marc
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Old 5th March 2003, 10:03 AM   #1006
Bricolo is offline Bricolo  France
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Quote:
Originally posted by protos
Well it shouldn't get hot at all with no input and no output.99% it's oscillation accordind to the tradition here.Check all your connections then since it seems you don't have the input pot tie a 50k or so from the inverting input to ground.

I'm using a 10K pot now (I can put the earpads out of my ears now )


I'm using peter's minimised gainclone shematic (but with no input cap for the momment)
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Old 5th March 2003, 10:26 AM   #1007
zeno is offline zeno  Europe
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Bricolo,

Check post 294 in this thread.



Actually the thread we are in now

Marc
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Old 5th March 2003, 10:45 AM   #1008
fedde is offline fedde  Netherlands
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Here you can find that post from Mr. K. Wang...

This is not just another gainclone

Fedde
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Old 5th March 2003, 11:10 AM   #1009
Bricolo is offline Bricolo  France
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Quote:
Originally posted by fedde
Here you can find that post from Mr. K. Wang...

This is not just another gainclone

Fedde

since I use a pot now, my -in is connected to ground with the 10K resistor, and the 10K pot

+in is directly to ground
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Old 5th March 2003, 05:17 PM   #1010
Bricolo is offline Bricolo  France
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I've tested the amp deeper this afternoon:


It still gets hot even at low volume, and even with no input signal



but when I change the load from a speaker to a 10R resistor, the chip runs cooler

can this be an oscillation problem? how can I fiw it?



I wish I had a scope
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