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Author Topic: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps  (Read 6201 times)

Steve Schroeter

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Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« on: February 21, 2011, 01:50:05 pm »

I'm planning to acquire a pair of SRX 718 subs, and wondering about the best route for amps for them.  Sound quality, budget, and weight are all important, and max. output less important.  I'd prefer to stick with QSC as my other amps are all QSC.

Many posts praise amps with (good quality) standard transformer power supplies for subwoofers, as compared with those using switching supplies, suggesting that the ability of the transformer supplies to handle the bursts inherent the low end (from bass and kick drum) are the key.  So, for example, an RMX 4050HD might be preferred to a PL340, both  bridged at 4 ohms, to handle 2 8-ohm subs or 1 4-ohm sub.

For similar cost I could run the pair of subs on 2 PLX 3402's each bridged at 8 ohms to provide 2200 watts per woofer, or 1 RMX 4050HD bridged at 4 ohms for both thus providing 2000 watts per speaker.  The 2 PLX's would save me 20 lbs. over the single RMX and could even be run on separate 15 amp AC circuits.

Has anyone experience comparing these 2 approaches?   Thanks, Steve.


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Gary A. Perrett

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Re: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« Reply #1 on: February 21, 2011, 04:29:47 pm »

This is a very common question here that seems to crop up over and over again. That's probably why you haven't gotten any responses.. it's an  ::)"Oh no not another which amp is best question"

If you want to do a search in the old forum you will find voluminous information...

I am here trying out the new forum so I'll try and see if I can't save you some time and effort and paraphrase some of what has been said in the past.

Most of the current amplifier offerings are decent choices, both old iron and new hi-tech power supply...there are however some that are considered better sub amps than others.

The XTi series Crown amps are not well thought of here for sub work...

The Crown Mt series, Itech and newer Macrotech amps are all considered excellent choices though spendy..

The lesser series like XLS etc just don't have the shear horsepower for sub duty on bug power hungry subs

The QSC offering (other then the GX series) seem to be pretty well received in the community inducing the PLX, and RMX series

Peavey has a long track record with their big iron, but have a new IPR series that are SUPER light but still have good reputations, and have garnered a fair amount of buzz around these parts...however their larger amps are not bridgeable and continue to be unavailable due to parts allocation difficulties (I gather from what is being bantered about) There are offerings of this amp design from Crest that will be heavier built and with some power supply modifications... and more expensive of course.

Many other amps ~ used a lot but not spoken of too much because of potential "quality" or serviceability issues. Most don't have enough output to be serious sub amps though...

Behringer, has a couple different amps, the older EP iron and the new EXP amps.. I've used both and other than a few issues with failures they work ok~ but again lack the output for serious sub usage The EP4000 appears to be a re-branded EP2500 that uses peak output specs to make it seem like a bigger amp, but rumor has it that it's the same internally...They have a reputation for greater than normal failure rates but I cannot verify that one way or another.

The thing here is that those subs are POWER HUNGRY... and if you want them to perform up to spec you'll need to power them as such.

My favorite amps right now without question are the Powersoft/Digam offerings... unbelievable performance and weight...but usually budget busters...

I am older then dirt so weight IS a BIG issue for me.. I'm definitely going smaller, lighter when I replace the big iron in my systems.

Gary Perrett
Twilite Zone Productions
Studio 'G'



   
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Steve Schroeter

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Re: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« Reply #2 on: February 22, 2011, 12:03:59 pm »

Thanks, Gary - a helpful of experiences with various amps.  Thanks for replying to that well-travelled topic.

For subwoofers though, is it better to use switching amp(s) with somewhat more power or standard transformer amp(s) with somewhat less power, as in the example in my original post? 

Specifically, ignoring weight and cost, which would be the better choice re: sound quality for powering 2 JBL SRX718S subs:
- 1 QSC 4050HD bridged at 4 ohms - 2000 watts per sub, or
- 2 QSC PLX3400 each bridged at 8 ohms - 2200 watts per sub?

All opinions gratefully received!

Thanks.  Steve
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Duncan McLennan

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Re: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« Reply #3 on: February 22, 2011, 01:30:26 pm »

There is no 'one size fits all' answer to that question. Neither switching nor transformer amps are better for subs.

At a given price point, a transformer amp might be a better amp than a switching amp of the same price. Then again maybe not.  The switching amp will certainly be lighter. If that's important to you, then it's better.

There are lots of different amps. Some are more reliable, some are lighter, some sound better on subs. It's always a tradeoff.

If I were going QSC to power 718s, I'd get a single PL380 and use it in stereo. It would allow you to add two more subs (even 4 more) without adding any amp.

If I had to chose from your options, weight and such not taken into consideration, I'd take the RMX. Of course with there is no situation in which I wouldn't consider weight, and I'd take the PLX for sure in any mobile application.
« Last Edit: February 22, 2011, 01:33:22 pm by Duncan McLennan »
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Tim McCulloch

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Re: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« Reply #4 on: February 22, 2011, 02:17:41 pm »

Thanks, Gary - a helpful of experiences with various amps.  Thanks for replying to that well-travelled topic.

For subwoofers though, is it better to use switching amp(s) with somewhat more power or standard transformer amp(s) with somewhat less power, as in the example in my original post? 

Specifically, ignoring weight and cost, which would be the better choice re: sound quality for powering 2 JBL SRX718S subs:
- 1 QSC 4050HD bridged at 4 ohms - 2000 watts per sub, or
- 2 QSC PLX3400 each bridged at 8 ohms - 2200 watts per sub?

All opinions gratefully received!

Thanks.  Steve

The power supply topology has less to do with this than you think, and you can't make blanket generalizations about a particular PSU topology being inherently unsuitable.  The Crown ITech have switch mode, PFC corrected power supplies and they STOMP on sub duties.

Depending on your program material, a particular amp might perform well or poorly.  Most of the amps sold today deliver rated power for a fairly short time to avoid pulling too much juice from the AC mains cord, and for live, Western hemisphere music it seems appropriate.  For EDM or other programs with sustained ELF content, an amp that delivers more continuous power might be a better choice.
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Mike Pyle

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Re: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« Reply #5 on: February 23, 2011, 01:31:17 pm »

Option 2. The PLX in my experience have worked fine on subs. I do read about people having difficulty with them when the a/c voltage drops to stupid low levels, hardly surprising. If I needed full output I'd rather have the option of running the amps on two circuits, as the RMX4050HD would likely trip a 15a breaker if you clipped it at 4 ohms bridged.

If you expanded the amp options to a higher powered PFC model that could power the subs in stereo, that would be different, but you are then at a higher price point.
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Steve Schroeter

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Re: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« Reply #6 on: February 23, 2011, 07:59:58 pm »

Thanks, gentlemen.

I guess Itech 8000 or QSC PL380 would be ideal.  But many places I work only have 15 amp AC circuits.

I have 2 QSC PL236's for monitors, that I could instead use for subs - 1 bridged per sub - and use PLX3402's for monitors.  Is there any reason why PL2s would be better than PLXs for Sub purposes?
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paul hanley

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Re: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« Reply #7 on: February 23, 2011, 10:30:24 pm »

I'm in a similar situation, and have found equipment reviews such as these rather useful:

http://www.abeltronics.co.uk/amptesting.php

Interesting is the distortion of the MA5002 at 40Hz...
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ProSoundWeb Community

Re: Sub Amp - 1 Transformer vs. 2 Switching Supply Amps
« Reply #7 on: February 23, 2011, 10:30:24 pm »


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