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Author Topic: QSC Amp Choice  (Read 6278 times)

Chuck Nottle

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QSC Amp Choice
« on: January 04, 2008, 01:42:46 pm »

I am looking to buy an either a PL4.0 or RMX4050HD. Both amps have similar specs and will be for 2 single 15" subs presently, but also buying for future needs.

Beside weight and cost, is there anything else I am missing between the 2 ??

I have read other threads and some seem to think that the weight of the power supplies matter when using for sub duty. Is there a really a noticeable difference?

Thanks for any input.
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Vinny D'Agostino

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Re: QSC Amp Choice
« Reply #1 on: January 04, 2008, 01:53:03 pm »

I switched from a QSC PLX3402 to a RMX4050HD and feel that there is a definite improvement in the sound of my subs using the 4050...
I can't compair it to the sound of the PL4 I have never heard one Crying or Very Sad
Would you be buying the PL4 new (old stock) or used?

Chuck Nottle

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Re: QSC Amp Choice
« Reply #2 on: January 04, 2008, 02:14:41 pm »

Hey Vinny,

Some of the recent threads seem to agree with you.

I am also using a PLX3204 on sub duty right now.  I know when I upgraded from a CE1000 there was a big difference in head room. Which is why I am considering a better upgrade.

I am looking at either 4050 new or PL4.0 used.
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Re: QSC Amp Choice
« Reply #3 on: January 04, 2008, 02:29:02 pm »

Well if you go with the 4050 new you get the 6-year warranty with it.
Shop Ebay for a *B* stock 4050HD you can get some good deals, that how I bought mine.

Chuck Nottle

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Re: QSC Amp Choice
« Reply #4 on: January 04, 2008, 02:52:42 pm »

As always, it comes down to Weight, Cost and Performance, not necessarily  in that order. It's the perfomance between the 2 that I am unsure of.
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Bob Lee (QSC)

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Re: QSC Amp Choice
« Reply #5 on: January 04, 2008, 06:40:14 pm »

One big difference is that the RMX4050HD is still being made, while the PL4.0 was discontinued some time ago.

If weight matters for bass, you can always add a barbell weight to the rack. Wink

The PL4.0 has a maximum gain of 80
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Mario Salazar

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Re: QSC Amp Choice
« Reply #6 on: January 05, 2008, 12:46:43 am »

I wonder if anyone can post the link on the discussion on why the weight of the PSU makes a difference.  I power my subs with 3402 and have thought them to be a bit wimpy (EAW 250RD2s) but I always thought it was the speaker not the amp.  THis is interesting, though I don;t want it to be true because my back hates the 77 lbs of the RMX 4050HD Embarassed
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John Roberts {JR}

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Re: QSC Amp Choice
« Reply #7 on: January 05, 2008, 10:43:35 am »

Mario Salazar wrote on Fri, 04 January 2008 23:46

I wonder if anyone can post the link on the discussion on why the weight of the PSU makes a difference.  I power my subs with 3402 and have thought them to be a bit wimpy (EAW 250RD2s) but I always thought it was the speaker not the amp.  THis is interesting, though I don;t want it to be true because my back hates the 77 lbs of the RMX 4050HD Embarassed


Weight only correlates with extra output (mostly thermal headroom) when the design is using the same technology. When mixing comparisons between different technologies all bets are off.

One example to make this point involves amplifier class. The old CS1200(x) was a fine amp for it's day (still is OK as long as you don't have to lift it) but because it is Class AB it requires more transformer and heatsink while putting out less power than smaller and lighter Class G GPS or PV models. Class D delivers even better efficiency, requiring less power from mains and heatsink, for similar output.

A second place in power amps where technology differences confuse simple comparison is the power supply. While HF switchers are sometimes criticized as being weak in bass region, there is absolutely no inherent design reason for that. A small transformer passing smaller packets of current, thousands of times more often than large transformer will be indistinguishable from old heavy iron. Just like with any design, it can be poorly executed and inadequate reservoir capacitance on the primary side could cause such symptoms. These primary reservoir caps are a size and cost constraint so it may be a place where some corners get cut.

Just like all conventional amps are not created equal, all switchers are not created equal. Don't try to judge an amp by the technology used, other than in general terms. Do listen to what other users report as that may reveal how well that technology is executed.

JR  
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Bob Leonard

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Re: QSC Amp Choice
« Reply #8 on: January 05, 2008, 12:39:51 pm »

This is a discussion that's been had many times. What you'll get for replies will be varied so the only thing I'll say is that I pulled a 3602 off of my subs and went to the 4050HD. I don't care about the weight and that has never been a part of my criteria when purchasing an amp. What I feel is a big part of amplifier performance is reserve power. In my opinion the use of a seperate power supply for each side of the 4050HD is a huge advantage, the reason for the additional weight, and the reason the 4050 seems to have endless power. I have not seen the 4050 clip since I put it to use and the amp runs cool to the touch all day long. There is a reason for the HD as in 4050HD. It stands for heavy duty, and the 4050 lives up to it's claims, and my subs have never sounded better. As for the PL4.0, if all things are equal I would still buy the 4050 because it's still a production amplifier and warranties do count. Good luck. Smile
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John Roberts {JR}

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Re: QSC Amp Choice
« Reply #9 on: January 05, 2008, 02:54:10 pm »

Bob Leonard wrote on Sat, 05 January 2008 11:39

This is a discussion that's been had many times. What you'll get for replies will be varied so the only thing I'll say is that I pulled a 3602 off of my subs and went to the 4050HD. I don't care about the weight and that has never been a part of my criteria when purchasing an amp. What I feel is a big part of amplifier performance is reserve power. In my opinion the use of a seperate power supply for each side of the 4050HD is a huge advantage, the reason for the additional weight, and the reason the 4050 seems to have endless power. I have not seen the 4050 clip since I put it to use and the amp runs cool to the touch all day long. There is a reason for the HD as in 4050HD. It stands for heavy duty, and the 4050 lives up to it's claims, and my subs have never sounded better. As for the PL4.0, if all things are equal I would still buy the 4050 because it's still a production amplifier and warranties do count. Good luck. Smile


I repeat my caution about trying to impute performance from technology (dual power supplies?) .

In fact the 4050 is similar to 1850 in design philosophy where the rail voltages are backed off, to give more thermal capacity but at some reduced peak power. The 1850, uses a 2450 heat sink and device complement, but only puts out 1850 peak.  Likewise the 4050 is a 5050 heatsink/power stage, running at cooler rail voltages.

This is just good conservative engineering, and more a variance in design details than a different technology. The 4050 trades peak power, for more thermal capability than the very similar 5050 due to a simple spec change of transformer voltage. For hard flogging a 2 ohm load the 4050 won't beat the 5050 for how loud it gets short term, but it will win for how long it plays loud.    

JR
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Bob Leonard

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Re: QSC Amp Choice
« Reply #10 on: January 05, 2008, 04:46:56 pm »

John Roberts  {JR} wrote on Sat, 05 January 2008 14:54

Bob Leonard wrote on Sat, 05 January 2008 11:39

This is a discussion that's been had many times. What you'll get for replies will be varied so the only thing I'll say is that I pulled a 3602 off of my subs and went to the 4050HD. I don't care about the weight and that has never been a part of my criteria when purchasing an amp. What I feel is a big part of amplifier performance is reserve power. In my opinion the use of a seperate power supply for each side of the 4050HD is a huge advantage, the reason for the additional weight, and the reason the 4050 seems to have endless power. I have not seen the 4050 clip since I put it to use and the amp runs cool to the touch all day long. There is a reason for the HD as in 4050HD. It stands for heavy duty, and the 4050 lives up to it's claims, and my subs have never sounded better. As for the PL4.0, if all things are equal I would still buy the 4050 because it's still a production amplifier and warranties do count. Good luck. Smile


I repeat my caution about trying to impute performance from technology (dual power supplies?) .

In fact the 4050 is similar to 1850 in design philosophy where the rail voltages are backed off, to give more thermal capacity but at some reduced peak power. The 1850, uses a 2450 heat sink and device complement, but only puts out 1850 peak.  Likewise the 4050 is a 5050 heatsink/power stage, running at cooler rail voltages.




This is just good conservative engineering, and more a variance in design details than a different technology. The 4050 trades peak power, for more thermal capability than the very similar 5050 due to a simple spec change of transformer voltage. For hard flogging a 2 ohm load the 4050 won't beat the 5050 for how loud it gets short term, but it will win for how long it plays loud.    

JR



Fully agreed and well noted John. There are actually three power supplies. In the simplest terms each side of the amp has it's own well to draw water from. It's proven to me that the 4050 works far better than the 3602 under more adverse conditions and it makes more sense to me that I sacrifice some db for longevity. I talked to my speakers just now and they have told me they are happy with the 4050HD also. As a matter of fact my 722s are asking for one as well. It seems a pair of them want more power than a pair of RMX2450s. What's happening is that I have a fairly varied collection of QSC amps and swapping them to compare performance vs speaker type. The losers go to the pile.
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John Roberts {JR}

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Re: QSC Amp Choice
« Reply #11 on: January 05, 2008, 06:33:05 pm »

Bob Leonard wrote on Sat, 05 January 2008 15:46




Fully agreed and well noted John. There are actually three power supplies. In the simplest terms each side of the amp has it's own well to draw water from. It's proven to me that the 4050 works far better than the 3602 under more adverse conditions and it makes more sense to me that I sacrifice some db for longevity. I talked to my speakers just now and they have told me they are happy with the 4050HD also. As a matter of fact my 722s are asking for one as well. It seems a pair of them want more power than a pair of RMX2450s. What's happening is that I have a fairly varied collection of QSC amps and swapping them to compare performance vs speaker type. The losers go to the pile.


All three sides?

Methinks you're talking about the three level class H power supply which is even more efficient than 2 level, which is better than old 1 level class AB. Again the 5050 also has the 3 level PS but won't hang at two ohms like the 4050 because of rail voltage tweak.

The 3602 could be a 2 rail amp so that would be a case of a higher technology (switching PS) front end connected to a less efficient technology back end power amp. In the margin the three rail class H will also pull more power from a limited  mains distro thanks to that improved efficiency.

So the 4050 is pretty high efficiency amplifier, with a conservative heat sink. Probably a good value, with plenty of thump.

JR






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Bob Leonard

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Re: QSC Amp Choice
« Reply #12 on: January 06, 2008, 01:55:15 am »

John Roberts  {JR} wrote on Sat, 05 January 2008 18:33

Bob Leonard wrote on Sat, 05 January 2008 15:46




Fully agreed and well noted John. There are actually three power supplies. In the simplest terms each side of the amp has it's own well to draw water from. It's proven to me that the 4050 works far better than the 3602 under more adverse conditions and it makes more sense to me that I sacrifice some db for longevity. I talked to my speakers just now and they have told me they are happy with the 4050HD also. As a matter of fact my 722s are asking for one as well. It seems a pair of them want more power than a pair of RMX2450s. What's happening is that I have a fairly varied collection of QSC amps and swapping them to compare performance vs speaker type. The losers go to the pile.


All three sides?

Methinks you're talking about the three level class H power supply which is even more efficient than 2 level, which is better than old 1 level class AB. Again the 5050 also has the 3 level PS but won't hang at two ohms like the 4050 because of rail voltage tweak.

The 3602 could be a 2 rail amp so that would be a case of a higher technology (switching PS) front end connected to a less efficient technology back end power amp. In the margin the three rail class H will also pull more power from a limited  mains distro thanks to that improved efficiency.

So the 4050 is pretty high efficiency amplifier, with a conservative heat sink. Probably a good value, with plenty of thump.

JR










No, there are 3 power supplies. One for each side and one common to both sides. Not 3 sides silly.
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John Roberts {JR}

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Re: QSC Amp Choice
« Reply #13 on: January 06, 2008, 10:34:16 am »

Bob Leonard wrote on Sun, 06 January 2008 00:55




No, there are 3 power supplies. One for each side and one common to both sides. Not 3 sides silly.


Not to continue harping on this, but...  

There is little if any practical benefit from two small power supplies vs. one big one. I can even argue that one big one is better. If we visualize what is going on in bridge mode one channel is drawing only from the plus rail(s) while the other channel only from the negative, and vice versa. Using a common PS means each channel can draw upon the full capacity of the whole amp's available current.

I suspect the supplies were split up for packaging reasons. Putting the rail capacitors right next to the output stages could reduce internal wiring losses, and the two could still be wired together, so they will share like one big one during peaks.  

I'm not trying to mystify amp design, technology can make a difference but IMO design execution is very important. The lads at QSC have plenty of practice and by now have pretty much figured out what works or not. Their different models are dialed in for different applications and pocketbooks.

JR

PS: Some audiophools will argue separate supplies improve crosstalk between channels but how do you measure crosstalk in bridge mode?
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Vinny D'Agostino

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Re: QSC Amp Choice
« Reply #14 on: January 06, 2008, 10:40:57 am »

um, yeah......anyway, I like how the 4050HD sounds which too me is all that matters Rolling Eyes

Bob Lee (QSC)

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Re: QSC Amp Choice
« Reply #15 on: January 07, 2008, 02:20:22 pm »

That is a correct read on the different amp models.

The RMX4050HD and RMX5050 do have two (not three) power supplies--a separate one for each channel. That is done primarily for packaging and manufacturing reasons.
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Chuck Nottle

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Re: QSC Amp Choice
« Reply #16 on: January 07, 2008, 03:25:02 pm »

Thanks for your input JR, Bob(QSC) and Bob L.

You have put some of the amp weight mojo to rest, in my mind anyways.

Best Regards.
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Bob Leonard

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Re: QSC Amp Choice
« Reply #17 on: January 07, 2008, 05:12:34 pm »

Bob Lee (QSC) wrote on Mon, 07 January 2008 14:20

That is a correct read on the different amp models.

The RMX4050HD and RMX5050 do have two (not three) power supplies--a separate one for each channel. That is done primarily for packaging and manufacturing reasons.



Bob,
That sounds a little different from what I was told the last time we discussed the 4050. Now I'm confused (more).
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BarryWillems

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Re: QSC Amp Choice
« Reply #18 on: January 07, 2008, 07:59:11 pm »

I ran 2 QSC 3402's (bridged mono) to power 2 JBL SRX series double 18" boxes for 4 years in a previous rock band project. This sub setup had plenty of headroom and the big JBL's ate it all up with no problem. (I also ran 2 more 3402's bridged for the double-15 SRX tops and 1 2402 stereo for the 2 JBL horns). We did lots of outside gigs in Houston heat/humidity and Galveston Bay salty air. Despite the 4 ohm loads on the bridged 3402's (2 ohms to the amp), I never had any thermal trips or other problems. Of course, I don't believe in running any power amps with the clipping lights glued on, and we rarely saw them at all with this setup. The only occasional issue was lack of AC power at the venue for everything.

I don't think 1 3402 stereo would be enough for both sub boxes, but the new 3602's are only about a grand and 21 lbs each, so load up the rack and bridge away if your drivers are up to it.

I can't comment on the how this would compare to 1 4050 HD for subs, except to say 2 bridged 3602's ought to deliver considerably more power at considerably less weight. Might be a bit more $$ for 2 3602's vs. 1 4050HD however.
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Walter Wright

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Re: QSC Amp Choice
« Reply #19 on: January 13, 2008, 03:42:01 pm »

still eagerly waiting for the original question, which was comparing the roughly equally-rated pl.4 and the 4050.
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Ryan Garnett

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Re: QSC Amp Choice
« Reply #20 on: January 13, 2008, 04:16:25 pm »

Stupid idea...PL340
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Walter Wright

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Re: QSC Amp Choice
« Reply #21 on: January 13, 2008, 06:02:52 pm »

sure, what the hell, itech 6000s for everybody! what about the original question?
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Bob Leonard

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Re: QSC Amp Choice
« Reply #22 on: January 13, 2008, 09:39:18 pm »

Walter Wright wrote on Sun, 13 January 2008 18:02

sure, what the hell, itech 6000s for everybody! what about the original question?

The answer is they have almost identical specs. and the 4050 is still in production. I am in favor of the 4050 over the PL4.0, own 4050s, have no problems and sleep better knowing I have 6 years of warranty to cover any problems and a $100 rebate for every one I bought. The rest is up to you.
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Walter Wright

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Re: QSC Amp Choice
« Reply #23 on: January 13, 2008, 11:50:05 pm »

please excuse any perceived crabbiness in my last post. i'm just genuinely interested in the specific answer because i recently acquired an older pl4, and want to know how it compares, especially for sub duty. no doubt owning new with a warranty is a fine thing, and psw has certainly opened my eyes to the respect that the rmx amps get as reliable bang-for-buck winners.

is this just rehashing a worn-out heavy iron vs. switcher debate?
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