Tickling the clip lights...

Marsellus Fariss

Marsellus Fariss

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Oct 25, 2011
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What's the general consensus on the effects on amps of running a rig up to where the clip lights flash ocassionally on transients? In this case the power provided theoretically shouldn't be enough to quite reach the peak SPL of the cabs (1250watts per EAW LA460) so I assume it's relativly safe for the cabs but is there anything else I should be aware of?I set the limiters to allow the Crown K2's "IOC" lights to blink a little but keep things outta clip. It's not my style at all to run things maxed out but BE's sure as #^*% will! It's been so long since I read up on the issue I could use a refresher. And I'll go ahead and answer the obvious "enough rig for the gig" question: we've put enough iron behind the cabs to get a mix to 105dbA at FOH (10 meters) and that's all we want to provide and we use all of it.
 
Re: Tickling the clip lights...

It doesn't matter from the amp's perspective. It can be useful information if you know the dynamic range of your music. 12db is a safe bet for anything that isn't highly processed (pre-recorded tracks from DJs, synth heavy music). Let's take 10dB since the math is easy, if your amp is good for 2000 watts and you're tapping clip lights you're probably not delivering more than 200 watts to your loudspeaker.
 
Re: Tickling the clip lights...

You asked what is the effect on amps. Grasshopper answered correctly that the amp doesn't care.

Yes the amp really doesn't care.

If the amp were capable of forming an opinion it might think.... (just kidding, amps really don't care).

JR

Note: this doesn't mean it's Ok to clip any part of your audio path... there might be people like me that care, but the amps, they don't care.
 
Re: Tickling the clip lights...

I'd be more worried about what's attached to the amp than the actual amp. Light clipping isn't going to hurt many components, even more so when it's a smaller amp. I'd only be worried about toasting HF drivers from clipping amps. HF diaphragms are more sensitive then paper cones...

Hell, just a few days ago I had a QSC RMX powered KF850 rig. It was plenty of boxes, but not nearly enough amp. The low and mid amps spent most of the night in clip, but they didn't do any damage because they didn't even have enough voltage to hurt anything.
 
Re: Tickling the clip lights...

Another thing to consider is that on many amps, the clip lights will start to flicker at 1/3 or even 1/8 rated power.

Ideally, you want your system to be able to get to the volume you want without ever seeing the clip lights. Then you know you've got enough rig. Of course, some operators will push things too far and you may get an occasional clip.
 
Re: Tickling the clip lights...

Brian jojade said:
Another thing to consider is that on many amps, the clip lights will start to flicker at 1/3 or even 1/8 rated power.

Ideally, you want your system to be able to get to the volume you want without ever seeing the clip lights. Then you know you've got enough rig. Of course, some operators will push things too far and you may get an occasional clip.
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I have never seen a power amp with "premature indication" of clipping. If anything I have seen some games played with none or very little hold on clip event indication (technically not a lie) and even some with finite attack times (arguably concealing brief clip events). Note: since most power amplifiers use unregulated power supplies the point of actual clipping is not easy to predict from input voltage. Most actually monitor divergence between actual output voltage and what it should be, so clip indication can also display for current limiting to prevents the output from following the input.

Two otherwise identical power amps playing side by side, one with a hold on clip event LEDs, and one that doesn't have any hold or has lag, could lead the uniformed consumer to believe that the amplifier under-reporting clip events had more available output power than the identical amp reporting correctly.

Perhaps to Brian's point, clip indicators are responding to transient voltage peaks which will not correlate well with loudness or heat content of audio waveforms.

JR
 
Re: Tickling the clip lights...

I don't know that Brian was suggesting the clip lights indicate prematurely. They will probably begin to light at 1/8 power or less entirely due to transient content in the music. The clip lights have nothing to do with the actual power delivered by the amplifier.

(I know you know this, JR, I am just trying to suggest that Brian is not wrong... probably).
 
Re: Tickling the clip lights...

Bennett Prescott said:
I don't know that Brian was suggesting the clip lights indicate prematurely. They will probably begin to light at 1/8 power or less entirely due to transient content in the music. The clip lights have nothing to do with the actual power delivered by the amplifier.

(I know you know this, JR, I am just trying to suggest that Brian is not wrong... probably).
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Bennett,
The clip lights should be indicative of the actual power delivered by the amplifier on peaks, but not the average power.

You wrote:
"Let's take 10dB since the math is easy, if your amp is good for 2000 watts and you're tapping clip lights you're probably not delivering more than 200 watts to your loudspeaker."

In your example, the peak power should be 2000 watts at some frequency, for some short duration of time, though the average power heating up the voice coil is only around 200 watts.

Depending on the amp and the clip light design, and the duration and frequency of the transient, the amp could be producing quite a bit more power than it is rated for when the clip light illuminates.

Some amps sound like crap as soon as the clip light flashes, others can be pushed another 3 -6 dB harder and still sound like music.

Art
 
Re: Tickling the clip lights...

Art Welter said:
Bennett,



Some amps sound like crap as soon as the clip light flashes, others can be pushed another 3 -6 dB harder and still sound like music.

Art
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Most amps do not sound like crap, from just tickling the clip lights, but driving the amp harder past clipping, makes the unregulated power supply part of your music as the amplifier output waveform remains pegged to + and - power supply rails for larger fractions of the signal waveform.

The power supply ripple voltage (nasty 2x mains frequency sawtooth) superimposed on top or LF bass waveforms will not be very musical sounding to most. How any amp sounds driven past clipping depends on, power supply reservoir capacitance, load impedance (2 ohms will obviously be worse than 8 ohms all else equal) and design. Regulated supplies like in PFC amps will just sound distorted (squared off) not distorted and raspy (sawtooth).

In general not driving any amp past clipping will result in better sound quality. If you don't operate outside the lines, how your amp operates outside the lines doesn't matter so much.

JR

Note: good clip limiters generally neck back the gain to reduce audible distortion related to clipping.
 
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Re: Tickling the clip lights...

Art Welter said:
Depending on the amp and the clip light design, and the duration and frequency of the transient, the amp could be producing quite a bit more power than it is rated for when the clip light illuminates.

Some amps sound like crap as soon as the clip light flashes, others can be pushed another 3 -6 dB harder and still sound like music.

Art
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I've been told this over the years. Doesn't this make it problematic to determine the appropriate safe amp power for a given driver?


Here's the real life example at hand:

The EAW LA460 has a 97db sensitivity and a 124db long term 130db peak rating. The math says it takes 500 watts to get it to 124 (long term) and 1995 to get it to 130 (peak). I've got 1250 on each cab witch will get it to just under 128db. 2db under peak. To actually reach the 130db peak rating the math says I need 1995 watts or 745 watts more per cab then the amps have. So would it be a true statement to say that the amps cannot drive the cabinet to peak? And that it's a pretty safe combination even when tickling the clip lights?
 
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Re: Tickling the clip lights...

It's safe to say the amp can't drive the speakers to peak with an undistorted signal. If a person ignores the clip light and keeps turning up, that same amp will likely be able to deliver enough power to cause damage. You probably don't want to drive your speakers to peak volume anyway - this metric is usually a level where the speaker won't die, but is beyond where the speaker sounds good.
 
Re: Tickling the clip lights...

Marsellus Fariss said:
I've been told this over the years. Doesn't this make it problematic to determine the appropriate safe amp power for a given driver?


Here's the real life example at hand:

The EAW LA460 has a 97db sensitivity and a 124db long term 130db peak rating. The math says it takes 500 watts to get it to 124 (long term) and 1995 to get it to 130 (peak). I've got 1250 on each cab witch will get it to just under 128db. 2db under peak. To actually reach the 130db peak rating the math says I need 1995 watts or 745 watts more per cab then the amps have. So would it be a true statement to say that the amps cannot drive the cabinet to peak? And that it's a pretty safe combination even when tickling the clip lights?
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It depends on how you are measuring the cabinet. First of all is your meter properly calibrated? And when was the last time it was?

Next what is the response time of your meter? if you use a faster response time-you will be able to see a higher peak reading. A slower response time will give a lower reading=more of an average if you will.

The normal "fast" response time is not fast enough to capture the short duration peaks. You need a peak or instintanious reading meter to actually see what the cabinets are actually doing.

just because your meter does not register it-does not mean that that sound is not there.
 
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