ahh. OK.Such a circuit would be preferable but it can only detect how close the output comes near the voltage rails.
It cannot detect clipping caused by current limiters.
One would also need input from the current limiters if one really is to monitor the output (the External input on the circuit)
It should always be in circuit b.t.w. if you want to have a clipping indicator in that specific amp.
Exactly. If someone can determine that the loudest they play is 20W peaks on a "135W" AVR, no need to even think about an external amp. If they determine they are hitting 120W peaks, well then *maybe* they are clipping and need to investigate further or just buy more amplification. So the idea is more a "ruling out" clipping than an exact determination.the goal of Head_Unit's proposal is obviously not to determine what an amplifier is capable of, but to help people become aware of the fact that his amplifier might sometime enter into clipping
*This is the hard part. The Stereophile 1st CD track 27 might work https://www.discogs.com/release/3692778-Various-Stereophile-Test-CD2
If someone could generate and upload suitable test tone(s) you would be the thread HERO!!
300 or 400 Hz at -20 dB is probably good since that will go into the woofers but without huge excursion, and also I dimly recall most voltmeters should be OK at those frequencies even if they are not good across the whole audio band.
I missed your post... I actually tried that but dropped the idea for reasons that now (40 years later) I do not remember. I think partly because the little clipping box with leads to the output was easier to attach than having to get a splitter to monitor the input, and I had to account for phase shift and delay through the amp with appropriate band limiting and integration. But a proper nulling circuit is a great idea.The way to do a simple circuit to detect clipping without characterizing the amp: make a differential amplifier with adjustable attenuation on inverting input. Split the power amp input signal and apply to non-inverting input. Apply power amp output to attenuator on inverting input. Play the power amp into speaker and adjust attenuator for minimum ac output of diff amp. The attenuated power amp output should almost match the input giving a good null. Now the diff amp will give a large signal when the power amp clips and its output no longer tracks the input signal accurately.
Long time ago I build a clipping detector as follows: A comparator simply drove a retriggerable c-mos one shot of 0.1s. Worked pretty well, also for very short pulses.Bandwidth/detection also an issue with my circuit above; to see clipping, I had to add an integration cap so the LED would stay on long enough to see unless you were constantly clipping (which often happened). Basically made an envelope detector. I also implemented a peak detector using the old National op-amp application book's circuit and I think that was the final version; it would detect a peak then slowly decay
"Sorry, this transfer has expired and is not available any more"Here you go:
Yup, another good idea. Back then I used a TTL one-shot but same idea. Probably a better way than the more complex integrator, but my circuit provided a bit of intensity modulation of the LED (brighter when clipping was more frequent) which was sort of cool. Not always a good thing as if I wasn't careful you could still miss a fast clip.Long time ago I build a clipping detector as follows: A comparator simply drove a retriggerable c-mos one shot of 0.1s. Worked pretty well, also for very short pulses.
Some early op-amps would invert when overdriven. Some power amps had similar behavior but it was resolved pretty quickly (either by fixing the amp or going out of business ). Overload behavior is why many of us advocate for such testing. The (a) problem for Amir @amirm is he really does not want to blow up an amplifier he doesn't own. And probably not one he does... Destructive testing gets expensive!Excellent point. I recall some AES paper (Matti Otala?) showing how some amplifiers had really ugly behavior upon clipping. One would snap momentarily to DC of the opposite rail voltage!
Here's some fresh ones then:"Sorry, this transfer has expired and is not available any more"
Be careful with test tones... You can fry your speakers with continuous test tones... A 100W speaker is designed to handle program material hitting 100W on the peaks with a much lower average average. And the tweeter can't handle as much power as the woofer.
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"Music is full of surprises such as explosive crescendos, combinant crests, blah blah."
Not with digital audio. You know precisely how loud the music can be.
This kind of blather has been used for decades to sell high power amplifiers, and it's a lie. It's always been a lie, but the hard amplitude limit of digital audio makes it clear.
Be careful with test tones... You can fry your speakers with continuous test tones
Yes, though the duty cycle would mean you couldn't use a voltmeter easily-I got one with "peak hold" then started wondering how good the peak hold actually was. Hence the qualification of using like 300-400 Hz waves, which should avoid such accidents as the power would go to the woofers, and the -20 dB scenario which is easy for the math. I suppose even -20 dB would be pretty loud, though any competent woofer should handle that long enough to make a measurement.Best way to test for clipping is to use sine burst with a 1:10 duty cycle, or better 1:100 duty cycle: