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[Dan Richardson]

I've had these QSC PLX3002 amps forever. Always solid indoors. Some years back, I discovered the thing where they go into voltage sag protect if they're on the end of too much AC extension. I've heard other people mention that as regards this specific model. I was on a 3kw Honda gennie last night, and they shut down again. Sure, get more line power. Sure, load the amps more gently. Unfortunately, there will always be the occasional show where specs can't be met. My PL2.4MBs are always running next to them, and they never shut down. I much prefer degraded performance to "click, no sound".

So, my questions, then, is this a PLX thing in general, or specific to the 3002? Are there other amps that people have noticed are liable to protect on voltage sag?

[John Roberts {JR}]

There is no magic*** to recover the losses from inadequate wiring but different amp designs can be more tolerant. The classic CS800 was well known to work down to silly low mains voltage, so it is pretty much a design decision about when to say no mas, and cut power.

Consider trying modern class D amps that will be more efficient but if you plan to use wimpy extension cords and soft power sources don't expect good results.

JR

*** PFC and regulated PS can stabilize power pulled from the wall, but there is no free lunch so if voltage falls, current increases to make the same power.... while you heat up your extension cord.

[Dan Richardson]

There is no magic*** to recover the losses from inadequate wiring but different amp designs can be more tolerant. The classic CS800 was well known to work down to silly low mains voltage, so it is pretty much a design decision about when to say no mas, and cut power.

Certainly all true. In my experience, and the anecdotal experience of some others, the PLX3002 is a little overzealous. As I said, my PL2.4MBs keep right on going. When I replace the PLXs, I'd like something designed to be a little more tolerant. It may well be a couple more PL2.4MBs. On paper, a single Peavey IPR2 7500 could replace the pair of PLX3002s in my application. I'm open to suggestions, but more looking for other amps to avoid.

[Brian Jojade]

The PLX is notorious for doing what you described. If the mains voltage drops for a fraction of a second, they will kick out.

The solution is to always oversize your power requirements when using those amps.

Something that is not often reported in the generic spec sheet provided by amps is how they handle poor power situations. This is something that certainly should be taken into account, as you will see it often when running portable rigs.

An amp with a good reserve capacitor system can handle voltage fluctuations much better than one that doesn't. Usually, you will see this in higher end, more expensive amps. However, it's never a guarantee.

At least the PLX amps let you know when there is a problem.  Other amps that work at lower voltage, but drop the power may leave you wondering why it sounds horrible, but you have no indication as to why...

[g'bye, Dick Rees]

The PLX is notorious for doing what you described. If the mains voltage drops for a fraction of a second, they will kick out.

The solution is to always oversize your power requirements when using those amps.

Something that is not often reported in the generic spec sheet provided by amps is how they handle poor power situations. This is something that certainly should be taken into account, as you will see it often when running portable rigs.

An amp with a good reserve capacitor system can handle voltage fluctuations much better than one that doesn't. Usually, you will see this in higher end, more expensive amps. However, it's never a guarantee.

At least the PLX amps let you know when there is a problem.  Other amps that work at lower voltage, but drop the power may leave you wondering why it sounds horrible, but you have no indication as to why...

Fixed it.  Headroom is desirable in every respect.

[Dan Richardson]

The solution is to always oversize your power requirements.

And in the real world, when you aren't given that option, you what? Go home?

[Dan Richardson]

The PLX is notorious for doing what you described.

PLX in general? It's always seemed to me to be the 3002 that people mention.

[g'bye, Dick Rees]

And in the real world, when you aren't given that option, you what? Go home?

I attempt to verify any on-site power pre-show.  I carry enough copper to augment or replace anything not up to the task.  Runs in excess of 100' are always suspect.

But my trump card is carrying my own Honda generators at all times.  I won't take the fall for inept providers.  My contract specifies my right to replace inadequate/dangerous gear with my own as well as the up-charge for having to do so.  This in itself is usually all it takes to get the right stuff.

That's my real world.

[Dan Richardson]

I attempt to verify any on-site power pre-show.  I carry enough copper to augment or replace anything not up to the task.  Runs in excess of 100' are always suspect.

But my trump card is carrying my own Honda generators at all times.  I won't take the fall for inept providers.  My contract specifies my right to replace inadequate/dangerous gear with my own as well as the up-charge for having to do so.  This in itself is usually all it takes to get the right stuff.

That's my real world.

This was on a Honda generator.

[g'bye, Dick Rees]

This was on a Honda generator.

Which was either under-sized for the job, located too far away on under-sized cabling or, less likely, being run in eco-mode which is suitable for static loads only.  Additionally, cleaning the air filters on both the generator and the amps will also help.  I find the generator is more stable when properly maintained  Mine are.

I'm not unsympathetic and should apologize for ducking your question regarding those amps.  In such a case, out comes my generator to supplement that provided, the load split accordingly.

Of course, lowering the overall level 3dB will hardly be noticeable but will cut system power draw significantly as you noted.  The 3000's put support a 23 amp max draw from the twist-lock connector, a tad more than the Hubble outlets.  How long was the cable run and what gauge?

[ProSoundWeb Community]