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Amp limiters... why cant i...?

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JonB67 View Drop Down
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    Posted: 28 December 2018 at 9:41am
Im wondering why people calculate their limiter settings.  

Im not particularly electronics or amp savvy. (Guess i wouldn't need to ask if i was)

Why can't you just unplug the speakers and measure the voltage with the amp set to 11 and dial the limiters down until its acceptable?

Its clearly not this simple as i can't find anyone suggesting this. What am i missing? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timebomb Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 9:52am
You can and its not a bad way to do it,  worth noting that some amps will drop there output under load more than other amps, ideally its better to do it with the speakers connected, even if its just for a quick check. 

Voltage gain / input sensitivity on amps is normally given at 8 ohms, and can change at 4 ohms and more so at 2 ohms, so calculating limiter settings has its draw backs too...   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 1:06pm
The main problem is that your speaker impedence is a moving target. It will change with frequency, so checking with speakers connected is pretty important. Calculations with a nominal 4 or 8 ohm is just guesswork. And as noted above, most amps will drop a few volts under load.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 1:33pm
Having some Tamp TA1400's, they have decent built-in limiters. Great behaviour in stereo (8ohm/ch) mode, limiting output voltage to somewhere around 64Volts/channel. However there is problems when driving low impedance loads / bridge mode @ 8ohm.  Severe clipping may occur as amplifier is unable to give 2x64V=128Volts.  Clipping starts at around 105Volts, long way before limiters will activate..

But as mentioned, speakers has moving impedance with frequency etc so limiting only input voltage is just guessing what happens in output stage..

 





Edited by Tonskulus - 28 December 2018 at 1:46pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 2:25pm
some amp owners manuals do recommend setting limiters up as you say. But I would advise that limiters are no substitute for a proper gain structure as part of a well-matched system which should be done first, then the limiters added as a last resort.
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JonB67 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 5:18pm
Originally posted by efinque efinque wrote:

I think the problem with limiters is that in addition to catching peaks they flatten the signal as well, which isn't a good thing in the long run... imagine applying a continuous, constant sine wave (or in worst cases near DC) for a prolonged period into a driver..

EDIT : an "ideal" DSP limiter is different of course

Did you even read my question? 
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JonB67 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 5:19pm
Ok. I'm up for trying this. 

Is there a guide or how to anywhere?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 6:47pm
Why would it have to be super accurate?

Ive got a fluke multimeter which will probably be sufficient,  but i wonder why you think it needs to be particularly accurate. Can you show me your workings?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 8:53pm
Originally posted by efinque efinque wrote:

Originally posted by JonB67 JonB67 wrote:

Why would it have to be super accurate?

Ive got a fluke multimeter which will probably be sufficient,  but i wonder why you think it needs to be particularly accurate. Can you show me your workings?

I think the logic board/LCD in handheld DMMs is too slow to react to sudden changes in voltages.

You think, or it is? Show me facts not guesswork.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote imageoven Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 10:23pm
I just googled analog multimeter,  one of the many that came up was under £7 so 'probably' not especially high quality or acurate.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 10:24pm
Originally posted by JonB67 JonB67 wrote:

Im wondering why people calculate their limiter settings.  

Im not particularly electronics or amp savvy. (Guess i wouldn't need to ask if i was)

Why can't you just unplug the speakers and measure the voltage with the amp set to 11 and dial the limiters down until its acceptable?

Its clearly not this simple as i can't find anyone suggesting this. What am i missing? 

The only thing that was not mentioned by the previous comments is... What exactly are you protecting? 

The majority of modern day amplifiers offer an on board limiter to prevent severe clipping. Most sound man use stand alone limiters to protect their loudspeakers from receiving too much power providing, the on board limiter in the amplifier is not adjustable. 

So are you protecting your loudspeakers from too much power or, are you using an amplifier that does not include an on board limiter in which, you need to use a stand alone limiter to prevent the amplifier from clipping?


Best Regards,  



Edited by Elliot Thompson - 28 December 2018 at 10:28pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2018 at 10:24pm
have you googled fluke?
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