| Bricolo |
I was playing on my workbench this evening, with my inverting gainclone, a scope and a function generator.
This is well know, gainclones have a very bad behaviour when clipping. I can't post illustrations because I don't have the digital camera right now, and I don't know how to connect my Tek 2232 scope to my computer to acquire data (if you know, tell me!), but the curve is really ugly!
But I saw another phenomen, that I haven't read about here: the input signal is deteriorated when the gainclone clips!
At first, I thought that my source was clipping, and that I was seeing the amplified clipping input signal at the amp's output. But when I disconnected the signal generator from the amp, and looked at the signal, it was perfect!
Any other feedback (this is the more appropriate word I found :)) about this phenomen? |
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| AMT-freak |
| That's an intrinsic problem of feedback amplifiers: Coupling stuff back to the input. If that's a clipped waveform, it'll show up as such at the input. |
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| Flemming J P |
And the back coubling can be real bad!!!
I managed to do something stupid (not uncommon :rolleyes: ) and this caused the magic smoke to leave the output cap's on my sound card :hot: (I was using it as source).
It was a lm3886 and I messed up by putting a 94uf cap in || with the resistor from - to mute, instead of from the mute leg and to ground.
I guess a non inverting opamp doesn't have this issue? |
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| ronc |
My quesion is why all of a sudden it started clipping when i didnt before?I had my home amp IGC (LM3875 300k/10 K loop, battery P/S +/- 24V) start clipping about 2 weeks ago and it is clipping at a lower power level than it did for about 6 months.Right now i am getting approx 4 watts before clipping.I really cant point out the actual point as my trusty old heathkit scope died.
ron |
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| Bricolo |
| Discharged batteries? |
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| Bricolo |
| How did you see it's clipping? Did you look at the output with a scope? If yes, what was the peak voltage? |
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| JOE DIRT® |
| maybe some bad cells in your batteries....I would try another power supply to verify this |
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| ronc |
Yes,i used my old Heathkit scope i built about 20 yrs ago.It died shortly thereafter.I believe its the CRT as i am gettig voltage to the crt.Happened last week.I Noticed the amp distorting so i hooked up the scope to the speaker leads and turned up the amp till i saw the signal start to flatten out slightly.Then i hooked up my heath signal generator to conferm.
I tested the voltage on each battery and all 4 measured within 12.4 to 12.72.
Sorry i am having a hard time typing as i had a cycle accident yesterday and my hand and sholder are messed up.
ron |
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