Questions about DBX Driverack PA+

[AntonZ]

There is no real need to set limiters for tops, as you will hear them distort. We limit the subs because you will not hear them distort.

Depends on who is riding the faders. I have seen DJ's happily pushing everything up way beyond the point where you start to hear freaking full on distortion. More blinking red lights = more good, for some people. Just to say there are morons out there that think it is only good with every knob and fader turned to the max. Responsible and knowledgable owners would know when to back off. Unfortunately it is not always them at the controls. If others drive your system: add limiters.

Mind you, I have no intention to bash all dj's, there are just as many out there doing a fine job. But that ignorant happy gaze together with bloody awful sound. What has been seen cannot be unseen. I sincerely wish I had never witnessed such events.

[loudsubz]

Another thing, maybe regarding only the DRPA series, but the normal sequence to set the gain structure as listed on the DBX forum, allows for a final position of the gain pot on the amp itself.

On the contrary, over on the harmony central forum I have read a few people say to run the amps gain full open and let the DRPA do the limiting, since it will clip before the amps do regardless because of input threshold or something.

Anyone know anything about that? I don't know if I would feel safe only letting my DRPA do the limiting and having my amps on maximum sensitivity.

[Bas Gooiker]

Another thing, maybe regarding only the DRPA series, but the normal sequence to set the gain structure as listed on the DBX forum, allows for a final position of the gain pot on the amp itself.

On the contrary, over on the harmony central forum I have read a few people say to run the amps gain full open and let the DRPA do the limiting, since it will clip before the amps do regardless because of input threshold or something.

Anyone know anything about that? I don't know if I would feel safe only letting my DRPA do the limiting and having my amps on maximum sensitivity.

Usually you'd set the limiter at full amp gain. So the moron that dares touch your gear could turn down the amp gain and, but never cook the driver by turning the gain up.

[Bruce Weldy]

Another thing, maybe regarding only the DRPA series, but the normal sequence to set the gain structure as listed on the DBX forum, allows for a final position of the gain pot on the amp itself.

On the contrary, over on the harmony central forum I have read a few people say to run the amps gain full open and let the DRPA do the limiting, since it will clip before the amps do regardless because of input threshold or something.

Anyone know anything about that? I don't know if I would feel safe only letting my DRPA do the limiting and having my amps on maximum sensitivity.

Usually you'd set the limiter at full amp gain. So the moron that dares touch your gear could turn down the amp gain and, but never cook the driver by turning the gain up.

Exactly....

[byacey]

According to the DBX gurus this doesn't render the best signal to noise ratio, but I would sooner put up with a slightly higher noise floor than having the cones turned inside out.

[Bruce Weldy]

According to the DBX gurus this doesn't render the best signal to noise ratio, but I would sooner put up with a slightly higher noise floor than having the cones turned inside out.

Amen....

[racertomtom]

According to the DBX gurus this doesn't render the best signal to noise ratio,

It’s my opinion that these “gurus” should meditate a bit longer. Limiters are nothing more than a failsafe and should have no effect on sound quality, regardless of where they are set, unless you run your system above the gain structure.

Let’s compare a limiter to a curb on the side of the road. It’s the driver’s job to keep the vehicle between the lines (gain structure). If you hit the outside line (headroom), you shouldn’t go any further. If you continue until you hit the curb (limiter), you should get back on the road. Under no circumstances should you drive with both tires against the curb, you will blow a tire or get a ticket (start to sound bad). If the engineer placed the curb against the line, then the curb forces you to stay on the road (limiter used in gain structure). If he placed the curb 3 meters away from the road (max speaker voltage), you will run through broken beer bottles and crap (sound very bad) before you hit the curb.

We need to add a step in the limiter setting procedure. Set and save your limiters, put the voltmeter away and set your gain structure. If you have to turn down your amp attenuators, so be it, but don’t reset your limiters. Your speakers will still be protected.

[byacey]

If you have to turn down your amp attenuators, so be it, but don’t reset your limiters. Your speakers will still be protected.

Fine until someone backstage starts twiddling knobs and opens up the level controls on the power amps.

It's better to ensure that no level settings can possibly be increased after the limiters.

Some of the earlier speaker processors had sense leads from the speaker terminals of the power amps. They would start limiting once the threshold was reached, regardless of the amp level control settings.

[Bill Fitzmaurice]

Usually you'd set the limiter at full amp gain. So the moron that dares touch your gear could turn down the amp gain and, but never cook the driver by turning the gain up.

True. But that's where you have it to set the limiter, not necessarily where you leave it in use. For maximum S/N you want the mixer running around 0dB output. You then set the amp attenuation for the desired sound level. If that's full tilt fine, but it's just as OK if it's at 12:00 too. Running the amp wide open and the mixer low to control levels can result in high noise.

[racertomtom]

Fine until someone backstage starts twiddling knobs and opens up the level controls on the power amps.

It's better to ensure that no level settings can possibly be increased after the limiters.

As long as you set the limiters with the amp knobs wide open you can turn them down and back up all you want, the setting never changes.

True. But that's where you have it to set the limiter, not necessarily where you leave it in use. For maximum S/N you want the mixer running around 0dB output. You then set the amp attenuation for the desired sound level. If that's full tilt fine, but it's just as OK if it's at 12:00 too. Running the amp wide open and the mixer low to control levels can result in high noise.

+1

[Michael Murphy]

RTT, so what your saying is that the DR PA+ with the mixer set at unity gain, although the amp gains are set at 100%, the amp will still not clip because the PA+ will compress then limit the signal so as to prevent clipping?. It makes sense what you said about setting it with the amp gains up and then backing them back down, in the reading Ive been doing I assumed that the amp gains would be left at full gain, however i did not think this would have been the optimum signal to noise ratio

[racertomtom]

RTT, so what your saying is that the DR PA+ with the mixer set at unity gain, although the amp gains are set at 100%, the amp will still not clip because the PA+ will compress then limit the signal so as to prevent clipping?.

No, I am not saying that! There are no absolutes here. The DRPA or PA+ will allow clipping anywhere below the limiter setting that clipping exists. If your amp is clipping at mixer unity gain, this might be a good time to turn the attenuators down. What I was saying is that it is OK to turn any or all the knobs if you need to, AFTER the limiters have been set.

[byacey]

I find the last few threads a little confusing. To clarify things, first of all your amp has to be able to swing whatever voltage you wish to set the limiter to, plus at least a little bit of reserve, otherwise the amp will clip before the limiter clamps down on the signal. For example, if the amp can only produce 54 volts flat out before clip, and you set the limiter threshold to 60V, the limiter will not prevent clipping in any way.

However, in the case of BFM's horn loaded designs, the limiter is set to prevent over-excursion of the voice coils, rather than preventing the amp from clipping. It's assumed that the amp is capable of exceeding the maximum recommended voltage of the particular enclosure. The truth be known, if the limiters are set correctly, the amp should never have the opportunity to approach clipping.

In the DRPA and PA+ you can choose to use compression in conjunction with the limiters , or not. I prefer to leave the compression off and just use the limiter function. Used in this way, the audio signal is unaltered and faithfully reproduced until you exceed the limiter threshold, and then you hear extreme compression. This hopefully becomes a blatant indication to the dummy pushing things to hard, to back off to a reasonable level.