Clipping Indicator Circuit

[IPunchCholla]

So I was looking for a lightweight (as in few components) clipping indicator circuit. I came across one on instructables, but now I can't relocate it. The biggest issue with it was it didn't indicate clipping until the output stage came close to the rails of the amplifier. From the measurements presented here, that of course is very far into clipping for most amps. Hype indicates in their data sheet (if I have done the math right) that the 300A1 clipping into 8 ohms happens around 34 volts, while its input rail is +55v. Anyway, I replaced the diodes creating voltage drop in the original circuit with a LM317HV. I am using R6 to put a 50mA pull on the 317HV and R5 is what you would want to use to control the clipping comparator. In the below example I have it setup to compare the incoming signal to that 34v limit.

Everything works fine in simulation. The red in the graph is the incoming output signal from the amp (in this case an attenuating sine wave). The blue line is the regulated voltage. The black line is the current flowing through LED D4 (the clipping indicator). But is this a reasonable way to go about this?

Does anyone here have any favorite universal clipping indicator circuits? In particular I would love ones that measure clipping more directly.

 

[DVDdoug]

(if I have done the math right) that the 300A1 clipping into 8 ohms happens around 34 volts, while its input rail is +55v. Anyway,

Really? I would expect that you can usually get to within a volt or two with most amplifiers. Of course, I'm talking about the peak of the sine wave, not the RMS. The power supply voltage might sag under load and then the amp would clip sooner than "expected". But that should take care of itself if the reference is the power supply or derived from the power supply.

I don't have the circuit but I made a clipping indicator a long time ago and I used comparator with voltage dividers (because otherwise the comparator couldn't handle the voltages). (The comparator was also powered by a lower voltage.) By playing with the voltage dividers you can set the trigger point as a difference between the output peak and the power supply so it would be possible to have several volts difference. I didn't have an oscilloscope so I probably just experimented and approximated it. I may have just cranked-up the amp with no-load and adjusted the reference voltage until it was triggering and then adjusted for a little more "sensitivity". And I think I triggered a 555 timer to hold the LED on long enough to see it.

 

[IPunchCholla]

Really? I would expect that you can usually get to within a volt or two with most amplifiers. Of course, I'm talking about the peak of the sine wave, not the RMS. The power supply voltage might sag under load and then the amp would clip sooner than "expected". But that should take care of itself if the reference is the power supply or derived from the power supply.

I don't have the circuit but I made a clipping indicator a long time ago and I used comparator with voltage dividers (because otherwise the comparator couldn't handle the voltages). (The comparator was also powered by a lower voltage.) By playing with the voltage dividers you can set the trigger point as a difference between the output peak and the power supply so it would be possible to have several volts difference. I didn't have an oscilloscope so I probably just experimented and approximated it. I may have just cranked-up the amp with no-load and adjusted the reference voltage until it was triggering and then adjusted for a little more "sensitivity". And I think I triggered a 555 timer to hold the LED on long enough to see it.

Really? I would expect that you can usually get to within a volt or two with most amplifiers. Of course, I'm talking about the peak of the sine wave, not the RMS. The power supply voltage might sag under load and then the amp would clip sooner than "expected". But that should take care of itself if the reference is the power supply or derived from the power supply.

I don't have the circuit but I made a clipping indicator a long time ago and I used comparator with voltage dividers (because otherwise the comparator couldn't handle the voltages). (The comparator was also powered by a lower voltage.) By playing with the voltage dividers you can set the trigger point as a difference between the output peak and the power supply so it would be possible to have several volts difference. I didn't have an oscilloscope so I probably just experimented and approximated it. I may have just cranked-up the amp with no-load and adjusted the reference voltage until it was triggering and then adjusted for a little more "sensitivity". And I think I triggered a 555 timer to hold the LED on long enough to see it.

It could be a misunderstanding on my part, filled in by selective data, but my impression was that while amps might be able to get within a couple of volts of the rails, there ability to do so without clipping was somewhat less than that. I'm probably not using clipping correctly, as I am a newbie at this.

 

[Rick Sykora]

There is this one…

Project 146

ESP Audio Projects - Overload indicator for mixers, preamps or power amps

www.sound-au.com

 

[mlloyd1]

If you can find the manual for the APT 1 Power Amp from the late 1970s, take a look at the schematic; it has a well designed clipping indicator.