Amps with clip indicators that fire at 3dB below actual clip?

Greg Cameron

Greg Cameron

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Jan 11, 2011
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On Yorkville's general info page, they claim:

"Most manufacturers set the threshold of their Clip LED's to fire at 3 decibels (dB) below the point of distortion. As a result, small amounts of Clip light activity are likely to be acceptable, however check your manual to be sure. In amplifiers with built-in limiters, Clip LED activity can indicate that the limiter is working."

Who is making amps where the clip indicator isn't indicating actual clip? This is news to me. It seems wasteful to indicate clip 3dB below actual clip as that the clip light would be lighting up at 50% of the actual rated output power for a given load.

Thanks,
Greg
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

Many devices light the clip or overload light before distortion so you have the opportunity to take action before the punters hear it. I believe the Yamaha digital desks do it or at least the 01V96 and LS9. Like your quote from Yorkville, it is mentioned in the user manual.
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

Hello Rob. Yes, I'm aware of this with digital mixers, My Venue has the ability to set the clip light threshold to whatever you want. But we're talking power amps here which are a different beast since the goal is often to squeeze as much juice out of a power amp as you can, rather than limit yourself by potentially wasting half the available power. I know that my Crest Pro series amps have actual clip detection to light the LEDs. And this is true of every amp that I've worked with. My other question is, how would a power amp "know" when it's 3dB below clip since the conditions before clip can vary based on load and available mains power? Wouldn't the amp have to clip before hand before a guestimate of what 3dB below clip would be? It seems true clip detection/indication would be much more simple to implement and more useful.

Greg
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

Greg Cameron said:
On Yorkville's general info page, they claim:

"Most manufacturers set the threshold of their Clip LED's to fire at 3 decibels (dB) below the point of distortion. As a result, small amounts of Clip light activity are likely to be acceptable, however check your manual to be sure. In amplifiers with built-in limiters, Clip LED activity can indicate that the limiter is working."

Who is making amps where the clip indicator isn't indicating actual clip? This is news to me. It seems wasteful to indicate clip 3dB below actual clip as that the clip light would be lighting up at 50% of the actual rated output power for a given load.

Thanks,
Greg
Click to expand...

Technically it's not a clip indicator if it indicates below clipping. In console design it's called a peak indicator and I recall back when I made serious recording consoles I would indicate 6dB before clipping or more. When I got into making lower cost Live SR mixers, that warning margin before clip grew smaller because customers in the value end of the market perceived such warnings as evidence the mixer had poor headroom. :-(

Power amps OTOH don't generally use any lead or safety margin before actual clip with LEDs that provide either very precise true clip indications, or even lag a little to under-report clipping.

FWIW intermittent transient clipping on relatively dynamic program material, with no hold-time to stretch out the LED illumination duration is not very apparent, so the occasional flash is not going to be very audible, but in my experience for most power amps, any clip light at all means actual clipping.

JR
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

OK - let's use the Crown Xti's as an example. What if you have the limiters set for say -3 and you are getting some red light flickers? Does that mean that it's telling you that the limiter is starting to clamp down when the red light flashes or is that a clip warning??
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

Gene Hardage said:
OK - let's use the Crown Xti's as an example. What if you have the limiters set for say -3 and you are getting some red light flickers? Does that mean that it's telling you that the limiter is starting to clamp down when the red light flashes or is that a clip warning??
Click to expand...

XTi limiters and indicators are a mess. First, the regular front-panel indicators show average, not peak. Additionally, they're showing INPUT level, not output level, IIRC. Except for the clip indicators, which again, IIRC, they show clip anywhere, output or input. You really need to have System Architect set up to monitors XTi amps, otherwise you really have no clue what they're doing. When the limiters are engaged it is quite possible to clip the inputs before the outputs get close to clip. Bad internal DSP gain structure can also make this happen. Personally, I sold all mine and will never use them again. It's more than worth the price to get 'real' amps IMNSHO. :lol:

Disclaimer: Crown is my favorite amp brand
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

John Roberts said:
Technically it's not a clip indicator if it indicates below clipping. In console design it's called a peak indicator and I recall back when I made serious recording consoles I would indicate 6dB before clipping or more. When I got into making lower cost Live SR mixers, that warning margin before clip grew smaller because customers in the value end of the market perceived such warnings as evidence the mixer had poor headroom. :-(

Power amps OTOH don't generally use any lead or safety margin before actual clip with LEDs that provide either very precise true clip indications, or even lag a little to under-report clipping.

FWIW intermittent transient clipping on relatively dynamic program material, with no hold-time to stretch out the LED illumination duration is not very apparent, so the occasional flash is not going to be very audible, but in my experience for most power amps, any clip light at all means actual clipping.

JR
Click to expand...

+1 … FWIW in a past life I reduced dynamic response of the clip light to increase power output and improve sales…. sadly it worked.
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

Peter Morris said:
+1 … FWIW in a past life I reduced dynamic response of the clip light to increase power output and improve sales…. sadly it worked.
Click to expand...

When the Crown DC300 first came out with a clip indicator ont he frotn panel-people complained that the new amp didn't get as loud as the old one (without an indicator).

So the joke is-What does it take to make a DC300 louder? 2 Pieces of electrical tape over the indicators.

now just run it untill you HEAR distortion.
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

Ivan Beaver said:
When the Crown DC300 first came out with a clip indicator ont he frotn panel-people complained that the new amp didn't get as loud as the old one (without an indicator).

So the joke is-What does it take to make a DC300 louder? 2 Pieces of electrical tape over the indicators.

now just run it untill you HEAR distortion.
Click to expand...
My home stereo has one each of the DC300 and DC300 Series II :) For a while I wanted another series II so I had the lights but since I have Pro Sound gear I can use, the home stuff doesn't get driven that hard any more.
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

John Roberts said:
FWIW intermittent transient clipping on relatively dynamic program material, with no hold-time to stretch out the LED illumination duration is not very apparent, so the occasional flash is not going to be very audible, but in my experience for most power amps, any clip light at all means actual clipping.
Click to expand...

I fired off an email last night to Yorkville inquiring about what amp manufacturers they were referring to and also if that's what they're actually doing with their amps. If I get a reply, I'll be sure to post it. But their statements really don't make any sense. Unless "most manufacturer' amps" have some type of microprocessor to compute 3dB below clip based on the actual load & AC mains voltage, how the heck are they supposed to reliably fire off the clip light 3dB below clip? And then how are you supposed to know when you are actually clipping if the light is lying to you and telling you're clipping when you've only used up 50% of your headroom. It's confounding and illogical to me...

Greg
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

Greg Cameron said:
I fired off an email last night to Yorkville inquiring about what amp manufacturers they were referring to and also if that's what they're actually doing with their amps. If I get a reply, I'll be sure to post it. But their statements really don't make any sense. Unless "most manufacturer' amps" have some type of microprocessor to compute 3dB below clip based on the actual load & AC mains voltage, how the heck are they supposed to reliably fire off the clip light 3dB below clip? And then how are you supposed to know when you are actually clipping if the light is lying to you and telling you're clipping when you've only used up 50% of your headroom. It's confounding and illogical to me...

Greg
Click to expand...

You don't need a microprocessor. You know Vout and you know Vrail. You can make a circuit that makes a red light blink at whatever point you want.
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

Except the Vrail in most power amps are not regulated so it can be a moving target in the process... True clip limiters generally don't attempt to look at the voltage, and instead detect when the amplifier is on the edge of losing negative feedback control of the output.

I guess a several dB before clipping LED could grab a reference from the unregulated supply that will track as the rails sag, but again, nobody I know wants to see 3 db before clipping.

JR
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

I don't think it's very useful either... but exactly what the meters do and how someone considers something useful is arbitrary in some respects. As long as you know what its reporting (or in this case, what it's *not* reporting) then you can make some decision of what to do and when.

I don't know the intricacies of amplifier and electronic design like you do JR, but I was simply pointing out this is nothing more than picking which segment of an LED ladder to call "clip" and doesn't require a microprocessor to do it. Whether other amplifier manufactures use any of these techniques is unknown to me.

I think the metering on all but the newest DSP enabled amplifiers often leaves much to be desired.
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

I can see how a simple comparator circuit could do that. But it really seems like a dumb idea to implement that on a power amp.
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

I'm surely repeating myself, but I'll try one more time.

The voltage rails of a power amp are generally not regulated, so 3 dB before clipping will be a different power at the the beginning of the night when cool, middle, and end when the amps (actually power transformer) are hot, not to mention mains sag from moment to moment with lighting or whatever..

In dBW not as much of a difference as in Watts which all the consumers seem to relate to. If somebody actually wanted -3 dB +/- maybe 1dB OK... for people wanting to see a lot closer to clip,, a simple voltage comparator is not as appropriate of a solution.

This is kind of amplifier inside baseball.. but the actual amps in the marketplace have evolved from decades of customers buying mostly what they want... while it sounds like a few models may be off the reservation a little.

JR
 
Re: Amps with clip indicators that fire at 3dB below actual clip?

John Roberts said:
The voltage rails of a power amp are generally not regulated, so 3 dB before clipping will be a different power at the the beginning of the night when cool, middle, and end when the amps (actually power transformer) are hot, not to mention mains sag from moment to moment with lighting or whatever..
Click to expand...

This was my initial thinking. The folks at Yorkville have not responded to my query as to whether or not they've implemented this form of clip indication with their amps, and as to which amp makers they're referring to that follow this practice. I suspect they won't. But it seems their website is dispensing false information. The reason why this came up is someone on the Rat message board had a question about amp output with their Yorkie amps. And then stated that most amp manufacturers clips lights light up 3dB below clip citing the Yorkville page, which led me to my post here. So some folks are buying into it. Not a good thing.
 
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