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Old 1st July 2011, 04:37 PM   #1201
fibko is offline fibko  Slovakia
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Quote:
Originally Posted by NMOS View Post
which inductor do you use ? Model and supplier ?
RM10 with airgap for amp. There are from old power supply.
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Old 2nd July 2011, 08:54 AM   #1202
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I have to make more tests, for now it looks good.

24vdc
5ohms load
24W output
Oscillating at 150KHz

YouTube - ‪firtst test audio amp d‬‏

I hope get about 200W with this board.

Last edited by electroconico; 2nd July 2011 at 08:57 AM.
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Old 2nd July 2011, 09:35 AM   #1203
luka is offline luka  Slovenia
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150k is too low for full range audio
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Old 2nd July 2011, 09:52 AM   #1204
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Originally Posted by luka View Post
150k is too low for full range audio
Yes.It´s slow , I´m working on.
It has gone up to 230KHz with other version and inductor cores.
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Old 2nd July 2011, 10:03 AM   #1205
luka is offline luka  Slovenia
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what is your industor size and output cap anyway?
but if you use many slow parts like very big fets and so on, you will have hard time getting high freq. I have 30uH and 470nF LFP filter and I have no problems going over 600kHz with it, so I I lower it to 480k or so
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Old 3rd July 2011, 08:44 PM   #1206
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I have the t106-2 core at 11uH , other core at30uH , other inductor 22uH .

The capacitor is at 1uF , other version it has 1.5uF
-----------------------------------------------------------------------
The smd version has 30uH inductor,1uF capacitor.

Now i got 45Watts at clippling limit at 20vdc with 5ohms load.
Vrms=14.8
R=5ohms
P= (V*V) / R


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Last edited by electroconico; 3rd July 2011 at 08:46 PM.
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Old 6th July 2011, 03:55 AM   #1207
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Originally Posted by fibko View Post
Amplifier run approximately on 250Khz with small noise. How I can start oscillate amplifier without signal? Because when I turn on, amplifier not oscillate.
I have the same problem,it does not start to self oscillate without signal input or at low volume.

It starts to work when I turn up the volume , it looks like a kind of trigger level.


Any suggestion ??

ty!
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Old 6th July 2011, 06:24 AM   #1208
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hello guys,try to implement a RC filter at output like 470nF+10 ohm/2W in this way the amp allways has a load at output and will start to oscillate
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Old 6th July 2011, 08:41 AM   #1209
81bas is offline 81bas  Germany
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Quote:
Originally Posted by electroconico View Post
It starts to work when I turn up the volume , it looks like a kind of trigger level.


Any suggestion ??
There is a well known solution for this problem: it is needed to connect 30K-50K resistor between positive rail and inductor input (directly after mosfets).

The problem is that sometimes the input integrator wishes to start the oscillation with positive pulse, but the bootstrap capacitor for high side driver is not loaded yet. If we place the resistor between amp output and positive rail, then integrator will detect the positive error at startup and will start the oscillation with negative pulse, which will effectively charge the bootstrap capacitor.
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Old 8th July 2011, 02:41 PM   #1210
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I've been contemplating this build since it was posted, but I have one question (which might show my ignorance of this circuits operation). Is there a reason why the LM311 is powered by only +/-3V? Anything wrong with using a higher voltage?
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