This is not just another gainclone - Page 101

Matttcattt · 5th March 2003, 08:31 AM

sorry, also had to do this, 1000th post in this thread!

Nuuk · 5th March 2003, 08:35 AM

Now go back to bed

Bricolo · 5th March 2003, 09:32 AM

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

protos · 5th March 2003, 10:00 AM

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.

zeno · 5th March 2003, 10:01 AM

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

Bricolo · 5th March 2003, 10:03 AM

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)

zeno · 5th March 2003, 10:26 AM

Bricolo,

Check post 294 in this thread.

Actually the thread we are in now

Marc

fedde · 5th March 2003, 10:45 AM

Here you can find that post from Mr. K. Wang...

http://www.diyaudio.com/forums/showt...&pagenumber=20

Fedde

Bricolo · 5th March 2003, 11:10 AM

Quote:

Originally posted by fedde
Here you can find that post from Mr. K. Wang...

http://www.diyaudio.com/forums/showt...;pagenumber=20

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

Bricolo · 5th March 2003, 05:17 PM

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

5th March 2003, 08:31 AM	#1001
Matttcattt diyAudio Member Join Date: Feb 2003 Location: Bristol	sorry, also had to do this, 1000th post in this thread! __________________ If it aint broke, don't fix it. If it is broke, fix it. If you can't fix it, take it apart and see how it "worked".

5th March 2003, 08:35 AM	#1002
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	Now go back to bed __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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5th March 2003, 09:32 AM	#1003
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR	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

5th March 2003, 10:00 AM	#1004
protos diyAudio Member Join Date: Mar 2002 Location: Athens+Ljubljana	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.

5th March 2003, 10:01 AM	#1005
zeno diyAudio Member Join Date: Aug 2002 Location: Belgium	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

5th March 2003, 10:26 AM	#1007
zeno diyAudio Member Join Date: Aug 2002 Location: Belgium	Bricolo, Check post 294 in this thread. Actually the thread we are in now Marc

5th March 2003, 10:45 AM	#1008
fedde diyAudio Member Join Date: Jul 2002 Location: Eindhoven, the Netherlands	Here you can find that post from Mr. K. Wang... http://www.diyaudio.com/forums/showt...&pagenumber=20 Fedde

5th March 2003, 05:17 PM	#1010
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR	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