Amp clipping...

[DJS]

Can anybody explain what causes this and how badly it can damage your speaker set-up, please?

I understand that its not good, and to avoid it at all costs, but with certain tracks i play, they seem to vary in volume which from time to time, if im not quite on the ball, i have caught the clip lights on the amp flickering (not permanently on)
Is this in speaker damaging territory, or is it down to how much into, and the duration of the clipping occurring?

Something ive never fully understood.

Thanks,
S.

[Excalibur]

Can anybody explain what causes this and how badly it can damage your speaker set-up, please?

I understand that its not good, and to avoid it at all costs, but with certain tracks i play, they seem to vary in volume which from time to time, if im not quite on the ball, i have caught the clip lights on the amp flickering (not permanently on)
Is this in speaker damaging territory, or is it down to how much into, and the duration of the clipping occurring?

Something ive never fully understood.

Thanks,
S.

As someone whose knowledge of this is experience, rather than paper qualifications, I reckon the occasional flicker is no problem at all. It's when the light comes on at full intensity for a prolonged period ( a second can be a long time, sometimes ;) ) that problems may occur. Do watch also that the red lights are not on at the mixer end, as that is not helpful either. Wait for someone to suggest buying a bigger amp!!

[JAMdisco]

Buy a bigger amp :p (thought I'd get this in first)

On a more serious note - I think Peter is right, occassional flicker should be ok, I've noticed mine doing it sometimes towards the back end of a 'young crowd' disco. I usually roll-off a little bass and this pulls it back into the green.

Note to self - need a bigger amp...

[Excalibur]

Buy a bigger amp :p (thought I'd get this in first)

On a more serious note - I think Peter is right, occassional flicker should be ok, I've noticed mine doing it sometimes towards the back end of a 'young crowd' disco. I usually roll-off a little bass and this pulls it back into the green.

Note to self - need a bigger amp..

No you don't. You need a bigger motor, to get all those cabs in! :p

[DJS]

Thanks for the replies.
Ive been contemplating a bigger amp for a while now, but for the moment i'll just have to keep on the ball with the clip indicators (maybe drop the bass slightly).

S.

[JAMdisco]

No you don't. You need a bigger motor, to get all those cabs in! :p

The cabs fit in fine (all 6 of em) it's the other stuff I have problems with. I feel a roofrack in the foreseeable future...:)

[Excalibur]

The cabs fit in fine (all 6 of em) it's the other stuff I have problems with. I feel a roofrack in the foreseeable future...:)

You could always downsize the subs. ;) ;) ;) ;) ;) ;) ;) :D :D

[Solitaire Events Ltd]

You could always downsize the subs. ;) ;) ;) ;) ;) ;) ;) :D :D

And buy some Mackies again...:D

[Excalibur]

And buy some Mackies again...:D

Sometimes your mischievous streak sits badly alongside the vision we all have of you as a successful, mature and level headed business entrepreneur, Darren. ;) ;) :D :D


Edit: To let you all in on the private joke, Justin has the larger subs, which were dearer than the small ones when I bought mine, hence why I have the small ones. I have a larger vehicle, and larger tops over my subs, which is why I'm attempting to persuade him to swap them. I'm having as much success there as persuading Tony that he should sell his Cortex, and save £250! :D :D :D :D

[nigelwright7557]

Can anybody explain what causes this and how badly it can damage your speaker set-up, please?

I understand that its not good, and to avoid it at all costs, but with certain tracks i play, they seem to vary in volume which from time to time, if im not quite on the ball, i have caught the clip lights on the amp flickering (not permanently on)
Is this in speaker damaging territory, or is it down to how much into, and the duration of the clipping occurring?

Something ive never fully understood.

Thanks,
S.

Clipping is when the amp tries to put out a higher voltage than its power supply can supply. The signal on the peaks then just stays at the max voltage of the supply voltage and so looks squared off on a oscilloscope.
This usually sounds pretty horrible.

The next logical step is to buy a bigger amp but make sure your speakers can handle the extra power.

Stepping back a bit more sensitive speakers might help with your old amp. The more sensitive the speaker the louder it is for the same power.

[501damian501]

what sort of system do you have ?

[JAMdisco]

Edit: To let you all in on the private joke, Justin has the larger subs, which were dearer than the small ones when I bought mine, hence why I have the small ones. I have a larger vehicle, and larger tops over my subs, which is why I'm attempting to persuade him to swap them. I'm having as much success there as persuading Tony that he should sell his Cortex, and save £250! :D :D :D :D

I'll tell you what then Peter (sorry this is off topic), when I do the paid charity gig for you on Saturday, how about we do a temporary swap so I can test them out. If I'm happy with them, then we have a deal :D
As you're out in (I think you said) Sheffield? we could do the exchange on Friday evening or Saturday morning (not too early though - I need my beauty sleep) :D

[Boogie Boy]

I'm from the old school of sound that says clipping is NEVER good.

For the amp to be clipping, presumably your mixer is too? Again, NEVER a good thing.

If you're having to play that loud, then bigger amp,more sensitive speakers, or a really good quality compressor are the only long term solutions.

BTW: Don't you trim the input signals going into your mixer, so that the tracks have roughly the same levels?

[DJS]

I'm from the old school of sound that says clipping is NEVER good.

For the amp to be clipping, presumably your mixer is too? Again, NEVER a good thing.

If you're having to play that loud, then bigger amp,more sensitive speakers, or a really good quality compressor are the only long term solutions.

BTW: Don't you trim the input signals going into your mixer, so that the tracks have roughly the same levels?


When you say the mixer is 'clipping', you are refferring to the meters going into the red (+db) zone?
Yes, admittedly i need a more powerful amp, which is on my shopping list.
I try to trim the input levels, but, from time to time i might over-look them.

What is the best way to set up a sound system for an event?
Surely there is a tried and tested method?
With that i mean, do you crank the amp volumes up, then bring up the master volume on the mixer to suit (obviously not slinding the faders to their max) then setting the gains for each channel last?

Cheers,
S.

[Boogie Boy]

Blinkin' 'eck. I'm truly amazed that a gigging DJ should ask such a question, as I thought it would be common knowledge.

What you should do is this.

1). Set amp to maximum power (others may disagree and you should certainly NOT do this if you're one of those guys who have under rated loudspeakers; that is only set amp to max if your speakers are RMS rated considerably more than your amp's RMS output in watts)
2). Trim input levels so that they peak at 0dB - + 3dB on the incoming tracks
3). Adjust mixer output to achieve the level of sound required (up to 0dB).

Once you've done this, UNDER NO CIRCUMSTANCES should you be tempted to take the inputs up further into the red, or take the mixer output higher than 0dB. Only do so if you are absolutely sure that the amp/mixer can take it without clipping. IF you're not getting enough sound, you're not getting enough sound and either bigger amp/bigger loudspeakers/more sensitive loudspeakers are required. Remember, that 1000 watts is approximately twice as loud as 100 watts into the same loudspeakers, so getting a 3K rig instead of a 1K rig isn't going to be that much louder. In essence, better/more sensitive loudspeakers are a fundamental solution that can give much more tangible results.

[DJS]

Blinkin' 'eck. I'm truly amazed that a gigging DJ should ask such a question, as I thought it would be common knowledge.
.

Well TBH, it might just have been the case that i simply had the bottle to ask the question in the first place.
There may well be people on here who do not know how to, and just choose to keep quiet to avoid comments like this.
- luckily now they do.
I know what i do myself, but its nice to check what others do, which reassures me that im doing things right.
If no-one asks these questions especially in the 'technical help' section, how are you supposed to learn?

Apart from that, thanks for the technical reply :)

S.

[JAMdisco]

I agree, I thik BB's post was rather insulting. I'm sure there are lots of 'gigging DJ's" that havent a clue how to set up a decent system. :rolleyes:

But, like you thanked him for, he did redeem himself by answering your question in the end. :)

[Solitaire Events Ltd]

I agree, I thik BB's post was rather insulting.

Welcome to my world...:sj: :D

[TonyB]

DJS, there are different ways to set up your sound system and it very much depends on what suits you best.

Do a Google for "gain structure" and you will probably get some differing opinions.

Setting the amp gains to full suits some people for differing reasons. One of the main reasons for doing this is that it can help prevent someone wacking the gains up while you are not looking and causing clipping/damage.

The down side of setting the amp gains to full is that you are also amplifying background noise (hiss and hum) which wastes power.

Likewise, the mixer master gain control should not be set to full as it will also give background noise.

It also depends on if you have input gains on the mixer or not.

The way I do it is set the amp gains to full then increase the master gain on the mixer until the background noise can be heard then back off with the master gain until the background noise goes away/is at an acceptable level.

Turn amp gains down to minimum. Play a CD (or other audio source) adjust channel volume so that the VU on the mixer is showing 0db (i.e. not going into the read). Increase amplifier gains until they just clip then back off a bit.

That way you will know that while the mixer VU is in the green, the amplifiers shouldn't be clipping without having to keep looking at it. By not having the amp level controls at max, you should also find that there is less background noise being amplified which means there is more power available for the music.

Depending on what the rest of your set up is, getting a bass bin (active or bi-amped) might help. It is the bottom frequencies that take the largest proportion of the power so using a bass bin should leave more power available for the tops.

If you amp has a higher power rating than the speakers, the level control on the amp will not make a lot of difference. It only controls the level of the input signal. An amp is quite capable of outputting full power irrespective of where the level control is if a stronger input signal is used.

[BrightLights]

Well said, TonyB. Boogie Boy's advice above isn't necessarily the right way to go about it. Check this out, taken from the following web page:

http://www.thenoizeworks.co.uk/tech2.html

"One of the most important and misunderstood areas of gain structure is the relationship between the output of a mixer and the input section of the power amp(s).
I, like many other musicians, until comparatively recently thought the best way to achieve the most output from a P.A. system was to turn the power amplifier gain controls up to full. However, this is not necessarily correct. The gain controls on power amplifiers are not ‘level’ or ‘volume’ controls. They are gain matching devices. They are used to match the output level of a mixer with the input section of the amp. Important: power amps are fixed gain devices - turning down the amplifier gain controls does not change the potential output of the amplifier, it only requires more input voltage to achieve it.
So why not just turn up the amplifiers gain controls up to full anyway? Well, the problem is that many amplifiers will clip with an input signal of +6dbu when the gain controls are all the way up whilst most mixing consoles can output +18dbu of output level before clipping. This means that you could be sacrificing 12db of the available output of your system!



I know it sounds perverse, but you can actually increase the available output of your system by turning the amps down. But the reality is that it is not a question really of turning the amps up or down, but a question of matching the output gain of the mixer with the input gain of the amp.
So how do we achieve this? You will need your mixer and amps for this as well as a test CD (if your lucky enough to have a mixer that can generate pink noise or has a sinewave generator this is not necessary.) Actually for most practical applications some modern music with lots of different
frequencies and a regular bass drum will probably do just as well.


The process is as follows:
1.) Connect the main output from your mixer to the amp(s). At this point do not connect the speakers (2kilowatts of pink noise is not fun!) - Actually, whilst most modern amps will happily run without a loudspeaker load, some older amps may not like it - best to check with the manufacturer (if there still around.)
2.) Set the amplifiers’ input attenuators to ‘infinty’ or ‘zero.’
3.) Generate pink noise via the mixer, test CD, or music CD. Pink noise is best because it contains the complete audable spectrum in equal amounts and is constant, music may not have all frequencies present and will have a rhyhmic ‘pulse.’ (If your using a test or music CD follow the guidelines above concerning channel gains.) Make sure no PFL or AFL buttons are depressed (so the mixers meters are showing the output gain of the mixer, not the input gain of a channel)
4.) Bring the master faders of the mixer up until your meters are just into clipping (usually the red portion) then back them off slightly so the clip lights are no longer on.
5.) Bring the input attenuators of the amplifier(s) up until it’s meters are also just into clipping, then once again back it off slightly.
The output gain of the mixer and the input gain of the power amplifier(s) is now matched. Performing this process not only maximises the systems headroom (output capability), but you can also tell from the mixer if your amps are clipping (distorting), since the amps now clip at the same level as the mixer. This will help protect your speakers. Anyone who has been through the expensive business of reconing speakers and replacing compression driver diaphragms know the potential damage a distorting amplifier can cause.
6.) Plug your speakers in and listen to some of your favourite music. Not only will it sound cleaner but your system will go louder before it distorts (i.e. it now has more headroom.)
So, if you think your system isn’t giving you what it should and your 2,000 watts per channel amp is sounding less than impressive, it may be a gain mismatch between the mixer and the amp - follow the above process and I’m sure the situation will improve.
Of course, this doesn’t just apply to your front of house system. The same process can be applied to any monitor and/or matrix systems you might be running."

[nigelwright7557]

I agree, I thik BB's post was rather insulting. I'm sure there are lots of 'gigging DJ's" that havent a clue how to set up a decent system. :rolleyes:

But, like you thanked him for, he did redeem himself by answering your question in the end. :)

At the end of the day to be a DJ all you need is a wad of cash to buy the equipment.
In fact you dont even need that if you have a credit card !

[Boogie Boy]

So the gain controls on an amplifier aren't volume controls? In that case why have anything to attenuate the signal? Why not have an amplifier with a fixed input?

Sorry, but the article from noizeworks didn't make a lot of sense to me in places. Setting gains to max (and maybe backing off a tad ) and setting mixers to 0dB in and 0dB out is the only 100% logical methodology.

Sure, you could have an amp sound louder at a 2 o'clock setting with the mixer feeding it more than 0dB, but that's not really the point, because the signal feeding the amp is likely to clip much more readily, as the mixer is being hard driven.

With most mixers, they will be set up for unity gain. In other words, an incoming signal that's hitting 0dB will be sent out of the mixer at 0dB (relative to the mixer's stated output in millivolts/dBA/dBV). Believe it or not, 0dB is there for a reason. Normally, it will be the level at which the mixer has best sound to noise ratio, sends a signal which is equal to its stated output and at which no clipping will occur/very low distortion occurs. That is, it's the level at which the mixer is working completely within its parameters at its optimum setting.

Mis-matching wil occur between amp and mixer if the amp's rated input is different to the mixer's rated output. In most piecees of gear, nowadays, these have been more or less unified. So, why one would need to mess around having mixer output levels set to +10dB for example or amplifier inputs/gains set to -10 db I really can't understand.

Hiss and hum shouldn't be a problem as most mixers will have a sound floor of -70dB or better and most amps the same or better. If you have lots of hiss and hum, I'd suggest you have the equipment looked at.

The most important thing is to use your ears. You'll soon know if the gear is sounding good or bad.

[BrightLights]

So the gain controls on an amplifier aren't volume controls?
No, they're gain controls. You can get just as much volume out of amp that's turned down low as one that's turned up full, you just need a louder signal going into it.


In that case why have anything to attenuate the signal? Why not have an amplifier with a fixed input?
Because you need to match the input level of the amp to the output level of the mixer it's connected to. Having no gain controls (or running it with them wide open, which achieves the same result) just means you'll have to compensate by turning down the output level of the mixer, which means you've got a lower signal to noise ratio and less headroom.


Sorry, but the article from noizeworks didn't make a lot of sense to me in places. Setting gains to max (and maybe backing off a tad ) and setting mixers to 0dB in and 0dB out is the only 100% logical methodology.
Unless you always run everything extremely loud, then that's not what you suggested. If you set input and output gains to 0dB and the amp on full, how do you control the volume? In your original post, you said you use the output level of the mixer, i.e. less than 0dB, so you attenuate the signal going into a very sensitive amp and amplify all the noise that's part of that signal. If we're talking logic, then wouldn't you want to preserve the best quality signal all the way through the system? Sure, you might have perfectly valid practical reasons for doing it your way, but it's not the only 100% logical methodology.


Sure, you could have an amp sound louder at a 2 o'clock setting with the mixer feeding it more than 0dB, but that's not really the point, because the signal feeding the amp is likely to clip much more readily, as the mixer is being hard driven.
Overdriving anything might cause it to clip. The point is to match the amp and the mixer so they both start clipping at same point. That way you know you're getting the best that each component can give before they both reach their limits. If you reach that point and it's still not loud enough, you need a better PA system!


With most mixers, they will be set up for unity gain. In other words, an incoming signal that's hitting 0dB will be sent out of the mixer at 0dB (relative to the mixer's stated output in millivolts/dBA/dBV). Believe it or not, 0dB is there for a reason. Normally, it will be the level at which the mixer has best sound to noise ratio, sends a signal which is equal to its stated output and at which no clipping will occur/very low distortion occurs. That is, it's the level at which the mixer is working completely within its parameters at its optimum setting.
Yes, and the point of a gain control is to match the incoming signal to that level - 0dB doesn't change, but the levels of incoming signals can be all over the place. Otherwise, why would we need gain controls at all? The same holds true right through the system, including the amp.

I'm not saying your way is wrong (and in fact I do something similar myself for practical reasons), but there are other ways that in a purely technical sense are more logical.

[Boogie Boy]

So much of what was written in the 'noize' article was done so to be contrarian and spread even more myths, IMO.

The fact of the matter is, that for all practical purposes, setting the amp level at max and feeding a mixer level that doesn't exceed 0dB (assuming that the amp's input and the mixer's output are roughly equivalent figures) is the best way to set up. You can always take the mixer output down and increase as necessary (up to 0dB) and be 100% sure that you aren't going to blow up any amplifier or speakers. If you don't follow this method, you can never be sure of anything.

As a way of further explaining and hopefully getting people to see the logic behind the thinking, consider a recording situation and the relationship between the multitrack, mixer and recording device.

Let's assume you have a 24 channel mixing desk. Some engineers would have the faders at all different positions (some at - X dB, others @ +Y dB, some at 0dB), others would have all the faders in a straight line (@ 0dB marking on the channels' strips). Imagine which one is able to (a) remember slight variations in a channel's level during the mix, (b) spend less time on the mix and (c) end up with less distortion and acceptable noise overall? If you're thinking the second, more methodical engineer, give yourself a pat on the back. Sure, in the old, old days, engineers would deliberately run inputs 'hot' to increase the s/n ratio, as analogue tape was very noisy without any Dolby or DBX noise reduction, but they did so at the risk of clipping and generally higher distortion figures.

[TonyB]

I don't think the 'Noize' article was done so to be contrarian and spread even more myths as if you read any article about setting up a gain structure, they nearly all say the same. Start at the mixer and work through the chain to the amp.

At the end of the day, set up your system the way you are happy with and the way you feel gives you the best performance. Just because others do it differently doesn't mean that they are wrong or spreading myths.