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Old 13th December 2012, 11:03 AM   #1511
Vostro is offline Vostro  Madagascar
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For sticking try a fast diode like uf4004 / Mur140 or better (not 1N4148) in parallel with miller cap (C10), with cathode on Q8 collector and anode on Q7 base.

Report back if sticking inproved

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Old 13th December 2012, 11:09 AM   #1512
AndrewT is offline AndrewT  Scotland
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That diode we talked about.
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Old 13th December 2012, 11:35 AM   #1513
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That diode we talked about.
when, where, why... what?
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Old 13th December 2012, 12:06 PM   #1514
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But before going forward with a solution, how can I identify the real problem?

Right now I see 3 possibilities for this happening:
1- the input current-mirror gets saturated
2- the VAS is sticking
3- the EF output is sticking

what can I check to identify the source of that issue? The solution will probably become obvious once I know it...

Martin.
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Old 13th December 2012, 12:16 PM   #1515
AndrewT is offline AndrewT  Scotland
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Vostro post a couple of days ago.
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Old 13th December 2012, 12:57 PM   #1516
a.wayne is offline a.wayne  United States
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Canonnica , what freq were you testing at , i could not tell from pictures posted ...
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Old 13th December 2012, 01:00 PM   #1517
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the names of the files, mouse-over
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Old 13th December 2012, 05:45 PM   #1518
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Default Non symetrical clipping produces nice results.

But if you want to fix it, to put it symetrical, then will loose some advantages you had.

Check it in your simulator and then decide what to do.

I am busy doing other things...this amplifier and any amplifier will clip.... some will clip first the positive rail, others the negative rail, others will clip both same time (aproximatelly same time).... you will continue to have clipping anyway..but if this bothers you..then remove the clipping.

The way i suggest, or just reduce your volume knob not to enter clipping...you know, in photography we go one or two steps down to avoid saturation (F Stops)...but always you will have a spot with saturation anyway...if counter the ligth, against the light.

I am not angry, not mad, not snobing your work...i really like it...but will like more if this does not deviate me from other newer projects.

This kind of clipping produces soooooooooooooo! nice results ...you will realise this soon.

Like everything in this life needs compromise....maybe some guy will perceive his wife is getting fat and he may say:

- Honey, you are getting fat!..please, try a diet sweety

Then sweet wife looses weight...and became thin..and the breast reduce a lot..then husband may say.

- Honey, please, stop the diet and get fat back again!

regards,

Carlos
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Last edited by destroyer X; 13th December 2012 at 05:56 PM.
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Old 13th December 2012, 06:00 PM   #1519
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Well, I don't mind right now about the asymetrical clipping, I worry more about the rail sticking.

When I observe sticking, If I go just 1 or 2 volts higher in the output, the amp starts to oscillate like mad and in a matter of a few milliseconds, the speaker protection engages, which returns the amp in a stable state because no more load is applied.
If I continue cranking with no load, I blow fuses because it goes crazy into oscillation.

Vostro has the best solution as of now. I cannot find any of the suggested diode locally, I ordered some that will arrive next week.

In the meantime, if anyone have another hypothesis, it's welcomed.

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Old 13th December 2012, 06:30 PM   #1520
AndrewT is offline AndrewT  Scotland
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Originally Posted by canonnica View Post
Well, I don't mind right now about the asymetrical clipping, I worry more about the rail sticking.
very definitely the correct priority.
Rail sticking is not nice, some of your pics are showing severe rail sticking.

And yes find why it oscillates. That is an indication that something is not right in a big way. there may be some ringing in there that gives a clue to what is going wrong. Can I seeing a ripple where the amp comes out of clip? I do see ripple in the clipped wave, but that might be rail ripple coming straight through the wide open output stage.
What about changing that MJE15032 in the VAS. It's far too slow and far too high capacitance for this duty.

Don't worry about small differences in clipping symmetry, it might be due to slight differences in rail voltage, either at the front end, or at the output stage end.
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