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Lower Input Sensitivity?

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immortal View Drop Down
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    Posted: 30 October 2013 at 1:56pm
I have a crown macro tech 2400 amplifier, in the manual it says it can either be set to 0.77v or 1.4v input sensitivity or a fixed gain of 26db, I thought it was set to 1.4v so have been giving it about 4db gain on the input, never really needed it any louder than this for the rest of my system.

I have recently built myself two more subs to power with this amp so decided I should probably check the switch inside the amp; It turns out its set to 2.2v? which I didn't know it could be set to. would be 3.6v if it was the fixed gain of 26db ( 2.2v on the lower models )

I have switched it to the 0.77v setting but is there much difference in how the amp runs if I am putting less signal in because it is having to amplify it more?

cheers


Edited by immortal - 30 October 2013 at 2:59pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 31 October 2013 at 11:08am
I used to work for a few sound companies that were equipped with dozens of Macrotechs.  I can remember seeing some of these which had the wrong labels over the switches. (Yes, I was surprised too...)

By the way, early versions only had two-position switches, for 0dBu Sensitivity or 26dB gain. Later production had the third position added, for 1.4V Sensitivity.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Grubbah Quote  Post ReplyReply Direct Link To This Post Posted: 31 October 2013 at 11:27am
Someone correct me if Im wrong, but i believe the benefits of having selectable input sensitivities would be when balancing a system with your other amps corresponding to relative gains...? I cant see why it would have any degrading effects on the amplifier with a lower input sensitivity.

I don't no though, could be wrong.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote immortal Quote  Post ReplyReply Direct Link To This Post Posted: 31 October 2013 at 11:59am
I reckon I will probably leave it at 0.77v it will be easier to manage.

is +6db to the input voltage double it so 1v +6db would be 2v?

so if I was to have it on 1.4v would I have to add about 5db of gain?

cheers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mattd Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2013 at 1:07am
I really late having amps that need 0.7v input voltage. Means I cant take a hot signal from mixer whilst running a zero without hitting my limiter settings. Is there any way of changing amps that have 0.7v to 1.4? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2013 at 1:10am
Originally posted by mattd mattd wrote:

I really late having amps that need 0.7v input voltage. Means I cant take a hot signal from mixer whilst running a zero without hitting my limiter settings. Is there any way of changing amps that have 0.7v to 1.4? 


Surely you just adjust the gain on that channel of your processor to compensate? Limiters should be set relatively…
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2013 at 12:54pm
Originally posted by mattd mattd wrote:

I really late having amps that need 0.7v input voltage. Means I cant take a hot signal from mixer whilst running a zero without hitting my limiter settings. Is there any way of changing amps that have 0.7v to 1.4? 


Yes, a 6dB pad on the input.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2013 at 1:21pm
Originally posted by toastyghost toastyghost wrote:


Surely you just adjust the gain on that channel of your processor to compensate? Limiters should be set relatively…


That works, and is often the best practical option,  but it's better to fix the amplifier sensitivity or gain to a more sensible figure.

Ideally, every piece of equipment in the signal chain should clip at the same point, so the meters on the desk indicate how much headroom there is throughout the system.

A modern high power amplifier with a sensitivity of 0.7V has too much gain for most applications.

In theory you're supposed to turn down the front panel gain control to match the amplifier's clip point to the rest of the equipment. But in our applications the gain control has to be set to maximum so that nobody can turn it up any further, because it's after the system limiters.

I remember two near-identical large festival sound systems. Same desks, crossovers, and speakers. One had Crest amplifiers, the other had Macrotechs. FOH engineers would occasionally use one system immediately after the other, at different festivals. Some of them would ask why one system was louder (and therefore, supposedly "better" ) than the other, based on how hard they were driving the XL3's.

The Crests all had 32 dB gain, whilst the Crowns were set to 26dB. Trying  to explain this to a non-technical person who just thinks louder is better, was a waste of time. We ended up setting the Crowns' gain switches to 0.7V and fitting pads on the PIP cards to match the gains...

(oh, and don't mention the Crests being pin 3 hot, that was a nightmare when combining  the two rigs for really big events...)


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Post Options Post Options   Thanks (0) Thanks(0)   Quote goodgroove Quote  Post ReplyReply Direct Link To This Post Posted: 09 November 2013 at 8:27pm
Hi i am one of those non technical people, my amp has 3 settings 1.4v / 32db / 26db which setting is best and why , it was on 1.4v when i got it ?
Thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote immortal Quote  Post ReplyReply Direct Link To This Post Posted: 10 November 2013 at 1:14pm
Its best to have it set the same as the rest of the system but i think in your case it is probably best to leave it at 1.4v.

what are you inputting into it from?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote goodgroove Quote  Post ReplyReply Direct Link To This Post Posted: 10 November 2013 at 2:29pm
Hi using an Aiien Heath xone 92 , Void Digidrive Plus
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