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seting gain on SS fortissimo active speakers


KidRay

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Just a quick query, I was setting my fortissimo 15A speakers up using pink noise from the Sound Check cd, as per the instructions, the clip lights just lit with the gain on 0db and the master volume at about 3/4. Is this ok or should I back off the gain a little so the master volume can be set higher?
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I have a conference system which is very similar ( Soundcraft Mixer/JBL Eon 15 Actives ), and I set this up in a similar way :- inputs to desk as dictated by their own levels, desk outputs at 0db, speaker gains approx 75%. This works in the vast majority of sittuations and gives me a little headroom on the speaker ( or a little protection!) if I need it.
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Personally I would not use pink noise to set up the gain.

 

Use the PFL and the material which will be played.

What's the application Kidray?

 

Hi John, it's after that point that I'm querying, it's mainly a vocal PA with some keyboards usually, I suppose I'd better expand my question. Once the gain structure is sorted on the mixing desk, then one would usually set the amp gains so that clipping/peak on the amps occurred at the same time as clipping/peak on the desk output, yes? Thus you are getting the most out of the system. (Please feel free to correct me if I'm wrong - as if you need telling!)

My quandary is that on the Fortissimos there is a both a gain and a volume pot, both of which affect the point at which the internal amps start to clip. So would you go unity gain and 3/4 volume or less gain and full volume, or something entirely different? It probably doesn't make a whole heap of difference, but I thought I'd ask if anyone had a better method for setting up the gain structure

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  • 5 weeks later...
If it were me, I'd probably set the volume at 0 and then the gain so that full output on the desk was a few db below clipping the amps. That doesn't mean to say it's the best way to go about doing it, it's just what I've always done and it's worked so I've stuck with it. Others may well do things differently!
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Personally I would not use pink noise to set up the gain.

 

Use the PFL and the material which will be played.

What's the application Kidray?

 

Hi John, it's after that point that I'm querying, it's mainly a vocal PA with some keyboards usually, I suppose I'd better expand my question. Once the gain structure is sorted on the mixing desk, then one would usually set the amp gains so that clipping/peak on the amps occurred at the same time as clipping/peak on the desk output, yes? Thus you are getting the most out of the system. (Please feel free to correct me if I'm wrong - as if you need telling!)

My quandary is that on the Fortissimos there is a both a gain and a volume pot, both of which affect the point at which the internal amps start to clip. So would you go unity gain and 3/4 volume or less gain and full volume, or something entirely different? It probably doesn't make a whole heap of difference, but I thought I'd ask if anyone had a better method for setting up the gain structure

 

Hi,

 

The usual gain staging technique is to have the amps on full beans, mixer stereo buss on 0db, this means the individual channel gains on the mixer will be as low as possible (less noise / feedback). Whilst I'm not familiar with the speakers you mentioned, having had a quick look on studiospares website the volume pot is the basic amp output level, the gain pot is input level which allows you to adjust for more gain if you are putting a mic straight in. For a line level connection (assuming both the mixer output and speakers input stages run at +4dbu - see manual) it should be set to unity gain.

As regards clipping, 0db on the desk (I'm assuming an analogue desk) is an average level (not peak) and assumes a certain ammount of headroom in the electronics for peaks.

I've just been informed my tea is ready so I should stop dribbling.................in conclusion amps full, input gain unity, desk output 0db, then you know when you are hitting 0db on the desk thats as far as you should push it.

(when you put the amps on full, depending on the electronics and venue electrics involved you might hit the noise floor (background hum) you can back the amps off a bit to minimise this, though you may find with a room full of chattering punters it makes no difference, and you can give it the full beans).

 

Hope thats helpful

 

Regards

 

Dom

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Cheers Dom, that makes a lot of sense. I think I need to back off the gain a little as the peak lights are coming on when gain is at unity and amp volume is at about 75% (when using our A&H desk. Our little Carlsbro desk that we use for a blues trio has a lower output).
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I also run amps with their gain all the way up, and limit levels further upstream, but my preference is to set the channel gain so the preamps are working within limits (i.e. not clipping), but fairly hard.

 

I have an A&H GL2200, and my impression is that the preamps sound best when pushed a bit.

 

Two reasons I can think of to justify this strategy: a) the channel preamps constitute a significant part of the cost of a desk both in design & electronic hardware terms, so you might as well get your moneys-worth and b) on the GL2200 at least, the mini-bargraph level meter on each channel needs some level to make it react, and they are a very useful visual indication of what is going on - often a handy addition to your ears if you've got a lot of channels on the go.

 

Cheers, Vince

 

Cheers Dom, that makes a lot of sense. I think I need to back off the gain a little as the peak lights are coming on when gain is at unity and amp volume is at about 75% (when using our A&H desk. Our little Carlsbro desk that we use for a blues trio has a lower output).
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I also run amps with their gain all the way up, and limit levels further upstream, but my preference is to set the channel gain so the preamps are working within limits (i.e. not clipping), but fairly hard.

 

I have an A&H GL2200, and my impression is that the preamps sound best when pushed a bit.

 

Two reasons I can think of to justify this strategy: a) the channel preamps constitute a significant part of the cost of a desk both in design & electronic hardware terms, so you might as well get your moneys-worth and b) on the GL2200 at least, the mini-bargraph level meter on each channel needs some level to make it react, and they are a very useful visual indication of what is going on - often a handy addition to your ears if you've got a lot of channels on the go.

 

Cheers, Vince

 

Cheers Dom, that makes a lot of sense. I think I need to back off the gain a little as the peak lights are coming on when gain is at unity and amp volume is at about 75% (when using our A&H desk. Our little Carlsbro desk that we use for a blues trio has a lower output).

 

 

Yes I agree with you, a good analogue board can sound better if you push it a bit, I do that myself, you have to be aware of what you are doing though in terms of gain staging (which I'm sure you are). To be helpful to kidray if he's putting his amps on full to make the most of the available headroom in the system, gain - input ciruitry on "unity" (not adding anything or taking anything away, which effectively takes them out of the equation). Assuming the ouput stage of the the mixer and the input stage on the active speakers both run at +4dbu he can do what he likes with the mixer controls, (though putting the main bus fader at 0db will help in terms of making the most of the available noise floor) as long as he doesn't send more than 0db from the desk he will be ok, and this also means the main bus level meters on the desk give a valuable indication of how much power he has left in the system.

Some people like to run the main bus much harder than 0db to get "that sound " from the desk, which would mean you would need to make a suitable adjustment before the amps. Its a balancing act dependant on taste, as long as the engineer is aware of the implications of what they are doing, then it's all good. The alternative is an "engineer" making red lights on the desk all night without thinking, and then complaining when the amps go into thermal protect and turn themselves off mid gig ;-) am sure we've all seen it.:-)

 

Regards

 

Dom

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