Members SteinbergerHack Posted December 18, 2009 Members Share Posted December 18, 2009 If I move the main faders past 0 Do you understand the term "gain structure"? The key questions here are: What is the maximum signal level at each stage in the chain from mic to speaker, and how does that relate to the "nominal" level for each in/out pair? What are you trying to accomplish? What are you trying to prevent? Link to comment Share on other sites More sharing options...
Members dboomer Posted December 18, 2009 Members Share Posted December 18, 2009 If I move the main faders past 0 Will the world end? What consequence of this are you concerned with? What are you worried that might happen? Of course you can move the faders past "0" ... depending on the situation. Sometimes you can move them way past zero. Link to comment Share on other sites More sharing options...
Members srp72ee Posted December 18, 2009 Members Share Posted December 18, 2009 The OP's original question is difficult to answer based on the information (and lack thereof). Based solely on the amplifier-speaker combination mentioned - I would definately have the clip limiters enabled and be reasonably cautious about driving the amp into limiting. Assuming the system is not bi-amped, is the DSP on the amp set to properly high pass filter based on the speakers? What is driving the amps (drive rack, crossover, EQ, mixer directly)? Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 18, 2009 Members Share Posted December 18, 2009 We disagree on this. Most mixers are capably of overdriving power amps by 15 - 25 dB. This is a lot like revving up your engine's RPM instead of simply changing gears to the appropriate one for the speed you want to go in that it is a big waste of signal to noise ratio. There is usually a much better compromise, namely turning down the input sensitivity controls by 10 dB (or more). 25dB??? The maximum output level of most mixers is between +24 and 26dB on true balanced outputs. The input sensitivity on most larger power amps is generally around +6dBU (average) which means that on a +24dBu mixer, with perfect gain structure, there is 18dB of headroom. Now it must be noted that many DSP speaker processors (like some of the the DBX Driveracks) have a maximum output level of between +18dBu and +20dBu, so now you have only 12dB of headroom, which is what I use as a target design number. That gives some leeway for improper gain structures, unaccounted for oopse factors etc. In this case, if you turn the amps down by 10dB, you have only 2dB of headroom between limiter threshold and clipping of the drive electronics. This 2dB of limiter compliance is inadequate IMO for any kind of live audio. Link to comment Share on other sites More sharing options...
Members madball24 Posted December 18, 2009 Author Members Share Posted December 18, 2009 I use the dbx driverack pa for everything. I don't have an equal used in it. I do rta the room. I use a mixwizard mixer Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 18, 2009 Members Share Posted December 18, 2009 You can turn the amp sensitivity down 6dB and still be ok. I would not go any more than that. Where do you have the limiting module parameters set at? Link to comment Share on other sites More sharing options...
Members dboomer Posted December 18, 2009 Members Share Posted December 18, 2009 25dB??? Yes!!! It is certainly possible. In fact using your figures ift could be 26 dB with an amp that drives to full with .775V. btw ... there are mixers that put out even more and there is DSP that does +30 dB:thu: Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 18, 2009 Members Share Posted December 18, 2009 Yes!!! It is certainly possible. In fact using your figures ift could be 26 dB with an amp that drives to full with .775V. btw ... there are mixers that put out even more and there is DSP that does +30 dB:thu: Not many that folks here are likely to encounter, in fact very few. And most amps are somewhere around 1.4-2.5 volts for rated output. The problem is that we may know these details but nobody else does, and frankly most of the stuff that is going to show up here is going to be in the 18-20dBu maximum drive level on dsp's such as the DR's and probably the Peavey DSP that you worked on. and this is under optimum gain structure conditions. I know several effective ways to effectively screw the gain structure pooch on some DSP's that I'm sure happen all the time. A few dB here and there and suddenly you have problems that you have no idea how they happened. I stand by my opinion that for the vast majority of users in the world using the typs of pieces encountered in the mid level real world, -6dB from full amp sensitivity is probably a good point to end up at, factoring in all the big picture, real world conditions. Funny, I'm a detail oriented engineer and I'm promoting the big picture and the real world conditions. That's not supposed to be part of my job description Link to comment Share on other sites More sharing options...
Members dboomer Posted December 18, 2009 Members Share Posted December 18, 2009 Not many that folks here are likely to encounter, in fact very few. And most amps are somewhere around 1.4-2.5 volts for rated output.) Exactly ... but since all the gear was never defined I gave a range of 15-25dB. It's most likely in the middle of that. Link to comment Share on other sites More sharing options...
Members RoadRanger Posted December 18, 2009 Members Share Posted December 18, 2009 I must be doin' somethin' wrong - I run the amps WFO and don't get any hiss or hum or any of that unless it's coming from one of the sources. How can I change my setup so it hisses, hums, and farts like one of them pro systems you all have? Link to comment Share on other sites More sharing options...
Members srp72ee Posted December 18, 2009 Members Share Posted December 18, 2009 Noise floor is not typically an issue with most modern equipment using balanced connections. Today's average equipment is much better than the early 80's equivalent. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted December 18, 2009 CMS Author Share Posted December 18, 2009 My system hasn't hummed at all since I taught it the words. Link to comment Share on other sites More sharing options...
Members mshifflett Posted December 18, 2009 Members Share Posted December 18, 2009 My system hasn't hummed at all since I taught it the words. This has to win post of the day! Link to comment Share on other sites More sharing options...
Members The Chinese Posted December 18, 2009 Members Share Posted December 18, 2009 Craig - Funny!!! hehehehehe Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 18, 2009 Members Share Posted December 18, 2009 My system hasn't hummed at all since I taught it the words. Hmmmmmm:poke: Link to comment Share on other sites More sharing options...
Members dboomer Posted December 18, 2009 Members Share Posted December 18, 2009 I must be doin' somethin' wrong - I run the amps WFO and don't get any hiss or hum or any of that unless it's coming from one of the sources. Smartass It depends on your requirements. You DO get both hiss and hum the question is, is it a problem? For loud rock bands it probably doesn't matter. For spoken word in a church it probably matters a lot. Somewhere in the middle is somewhere in the middle. In any event ... with whatever you've got if you turned the amp down by X dB and the mixer up by the same X db you system would enjoy an increase in dynamic range of that X dB. Andy suggests 6 dB, I say 10 db. Not a very big change either way , it depends on your skill at operating the mixer. Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 18, 2009 Members Share Posted December 18, 2009 It depends on more than this. It depends on the MOL of the driev electronics, the liklihood that somebody else may operate the system, having enough PA for the job, having common sense and other factors, all of which are typically in short supply in the market most of the forum members operate. Link to comment Share on other sites More sharing options...
Members madball24 Posted December 18, 2009 Author Members Share Posted December 18, 2009 I have my limiter set at 0 db is that okay Link to comment Share on other sites More sharing options...
Members The Chinese Posted December 18, 2009 Members Share Posted December 18, 2009 yes. just make sure you mix is setup close to 0 as well. Link to comment Share on other sites More sharing options...
Members RoadRanger Posted December 18, 2009 Members Share Posted December 18, 2009 all of which are typically in short supply in the market most of the forum members operate.Yes, I do tend to be maxxed out on the subs and even push into the clip limiters so I really would rather have the extra headroom that running the amp WFO gives there - plus subs seldom hiss . But even on mains using an RMX2450 WFO I have to stick my head up within a foot of the speaker in a relatively quiet room to hear any hiss so I just don't have any reason to attenuate the amp down. Link to comment Share on other sites More sharing options...
Members dboomer Posted December 18, 2009 Members Share Posted December 18, 2009 I have my limiter set at 0 db is that okay Assuming you are talking about a limiter to protect the speakers ...that probably doesn't have any relevance at all. I have outlined how to set a limiter in the sticky - guide for goobers - post 24 You need toknow that the printed "0 db" on gear means very little, sometimes nothing. Especially if your gain structure is not set "properly" Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted December 18, 2009 CMS Author Share Posted December 18, 2009 I have my limiter set at 0 db is that okay Depends. Why is it set there? Link to comment Share on other sites More sharing options...
Members madball24 Posted December 18, 2009 Author Members Share Posted December 18, 2009 I was old that setting it at 0db would stop anything from going past 0db when i do the drive rack setup it sets the limiter at +12db is that usual? Link to comment Share on other sites More sharing options...
Members SteinbergerHack Posted December 18, 2009 Members Share Posted December 18, 2009 I was old that setting it at 0db would stop anything from going past 0db 0 dB referenced to what? What is the nominal level of your output, and what is the nominal input level of the power amp? Link to comment Share on other sites More sharing options...
Members srp72ee Posted December 18, 2009 Members Share Posted December 18, 2009 subs seldom hiss . Only heard subs hiss once. Didn't here anything else from them the rest of the night. Sure did smell funny though. Glad they weren't mine. Link to comment Share on other sites More sharing options...
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