Amp clipping question.

[killa]

So I am managing to clip a crown xls 1500 while powering two fearful 12/6 cabs and it seems like they can take more. I am wondering though if the clip lights might come on due to a lack of good power (lights in practice space are starting to dim :eek or do the lights come on only when the amp reaches a certain output voltage meaning that is all it has?

Put another way is that all the amp has or is that all the amp has available due to lack of good power? I don't know how the amp senses clipping.

[Sydney]

Re: Amp clipping question.

... (lights in practice space are starting to dim :eek ....

I'd be measuring voltage drop.

[billfitzmaurice]

Re: Amp clipping question.

I am wondering though if the clip lights might come on due to a lack of good power or do the lights come on only when the amp reaches a certain output voltage meaning that is all it has?

You'd have to ask Crown to be sure, but the clip lamps might be activated by the amp output voltage or by the post input attenuator signal voltage. The lack of sufficient power probably wouldn't have any effect on the clip indicators, but the dimming lights should be telling you that you're overtaxing the current capacity in your practice room, and that's a potential safety issue.

[wg_ski]

Re: Amp clipping question.

Most amps have some method of detecting actual clipping. The method varies, but the indicator comes on when the peak output voltage is somehow limiting. If the voltage at your power socket is sagging, the amp will clip sooner. It may only be 1dB or less down when you see the ceiling lights flicker.

Music has peaks that are many times in excess of the average. You'd be surprised how often you can clip and have it not be audible. And how much lower the average power (which is percieved as loudness) is, even when the clipping is more or less continuous. Also, the AC current draw of these amplifiers is many times in excess of the rating on the panel when actually driven to clipping. These peak demands are short, and the average under heavy clipping will be around the stated value. Crown used to publish current deamand for their amps with sine wave, 1/3 and 1/8 power - and those sine wave numbers can be crazy high. But every time the bass hits, it does draw that much for an instant, and the momentary voltage drop you get on the AC mains is consistent with that much current draw. Like a refrigerator starting on every drum kick.

[killa]

Re: Amp clipping question.

but the dimming lights should be telling you that you're overtaxing the current capacity in your practice room, and that's a potential safety issue.

Was thinking the same thing but we practice out of a storage shed and I doubt the owner would do anything about it. Probably is caused by long runs of copper.

[billfitzmaurice]

Re: Amp clipping question.

Was thinking the same thing but we practice out of a storage shed and I doubt the owner would do anything about it. Probably is caused by long runs of copper.

Perhaps the real possibility of said shed burning down would change his attitude. :eek:

[killa]

Re: Amp clipping question.

Well I found out this amp has a clip limiter and it seems to help. It was only clipping on the initial string strike (I play hard) when the string strikes the fret and apparently the xls amps just shut off if they clip hard where other amp topologies just distort a little and only shut off if they get too hot. With the "peak x" limiter engaged it hasn't shut off and has been able to put out more power.

Also for anyone trying to use the limiters. I thought mine were on because they said "on" but they weren't really on until I hit the button to save the settings.

[killa]

Re: Amp clipping question.

I spoke too soon :( The amp still shuts down occasionally, just not as often. Guess I should have went with a bigger amp.

[Paul O]

Re: Amp clipping question.

I spoke too soon :( The amp still shuts down occasionally, just not as often. Guess I should have went with a bigger amp.

Nobody has asked yet so how do you have the amp configured and what is the speaker load on it?

[killa]

Re: Amp clipping question.

Well I was wrong again. :o I had a issue with my main bass so I took my backup. My backup has much hotter pickups and can light the gain light on the preamp very well like it should (my main bass doesn't keep it lit near as well).

Due to me not getting the memo, no one was at practice except me so I took it upon myself to trouble shoot my rig. Well with no one else using power I can crank everything all the way and barely get the clip light to light even with a hotter signal from my bass.

My main hypothesis is that the clip light comes on (and protect mode) when the voltage rails sag and they sag much earlier when others are using their amps.

My second thought (although I don't see how) is that it might be due to gain staging? I don't see how this could be but it is the only other thing that changed.

[killa]

Re: Amp clipping question.

Nobody has asked yet so how do you have the amp configured and what is the speaker load on it?

Think I have it figured out now (see above post). Amp is in bridged mode with 80hz highpass. Speakers connected in parallel to get 4ohm load.

[Paul O]

Re: Amp clipping question.

My main hypothesis is that the clip light comes on (and protect mode) when the voltage rails sag and they sag much earlier when others are using their amps.

That is the right conclusion, digital amps like this require a very stiff AC supply and by the sounds of it(dimming lights) that is exactly what you don't have in this practice space.

[Brian Steele]

Re: Amp clipping question.

Think I have it figured out now (see above post). Amp is in bridged mode with 80hz highpass. Speakers connected in parallel to get 4ohm load.

I don't think it's "clipping" that's causing the issue. I think something is causing your amp's protection cuits to think that its output is seeing too low an impedance, so it's engaging. Instead of using the amp in bridged mode to drive those speakers, try hooking them up with one to each channel. If the input power to your amp is indeed limited, all you'll need to do is turn up the gain a little to make up for the new configuration, and I've I'm right, even if your amp does clip, it will no longer engage the protection circuitry.

[wg_ski]

Re: Amp clipping question.

It was only clipping on the initial string strike (I play hard) when the string strikes the fret and apparently the xls amps just shut off if they clip hard where other amp topologies just distort a little and only shut off if they get too hot. With the "peak x" limiter engaged it hasn't shut off and has been able to put out more power.

Sounds like the peak limiters were limiting the average power.

That is the right conclusion, digital amps like this require a very stiff AC supply and by the sounds of it(dimming lights) that is exactly what you don't have in this practice space.

And too much average power requires too much AC current. You're probably activating the power supply's undervoltage lockout, not the amplifier's over current protection circuitry. This is common with big car amps when used with stock alternators. And the reason I'm still using big iron for sub amps even though class D is "better". When I can afford ones with unviersal voltage and PFC, then I'll consider it.

It seems unlikley, however, that you'd draw enough to cause serious problems just driving tops high passed. Just how loud are you playing in this "practice" space? Or is the AC wiring really bad enough to be a fire hazard?

[killa]

Re: Amp clipping question.

It seems unlikley, however, that you'd draw enough to cause serious problems just driving tops high passed. Just how loud are you playing in this "practice" space? Or is the AC wiring really bad enough to be a fire hazard?

Not tops, bass cabs. My bandmates like to practice LOUD! and these cabs aren't the most efficient so they like a lot of power. As far as the wiring I doubt it is a fire hazard or it would have went up in flames long ago. The lights really use to dim a few years ago when there were multiple bands playing at the same time :eek: My old ampeg br1 use to make the lights dim quite severely back then and it was only a 350w head.