Amp upgrade

Randy Gartner

Randy Gartner

Junior
Jan 12, 2011
465
18
18
72
Pennsylvania
randygartnersound.com
A few months ago, I asked about up grading my sub amps from 2 -QSC PLX 3402's to 2-Lab Gruppen FP 3400's to power my 4 double 18 subs. The 3402's are rated at 1100 watts per side at 4ohm and the FP 3400's rated at 1500 watts per side at 4ohms.I was told I would not be able to hear any audible difference by increasing the amps by 400 watts. I'm here to tell you you were wrong. I run 4 way and use the FP's on the subs. I could immediately tell the difference not only in the audio level,but in the punch too. In fact, I was running my Ashley Protea at + 11 with the QSC's and had to turn it down to + 8 with the Labs. I moved the 3402 to the lows and the 3002 that I had on the lows to mid duty. I have a Lab Gruppen FP2400 on the highs. My console is a Midas Pro1. I wasn't the only one who noticed the difference.Thanks to Steve Payne for selling me the amps.
 
Then what you are hearing is not reflected by the spec sheets.

I'll bet if you upgrade your amps again with another step up in quality, you will hear another level of performance improvement.

How amplifiers behave with a real world source connected to one end and a loudspeaker cabinet wagging the other end is not easy to describe on a data sheet. It should be easy, gain is gain and voltage into an impedance is watts... but as you can hear after this upgrade, it isn't really that simple on a spec sheet.
 
With both Lab and QSC amps in inventory I can underscore the improvement in sound when using the Labs in place of QSCs on most speakers. If however you had to adjust the gain on any amp to bring the relative balance back to normal that is entirely a gain difference rather than a difference in amp 'quality'. While the QSCs have no gain set switch in the manner of the front panel markings are in db of attenuation from the full rated gain and are as good a start as cheap chinese Alps pots will permit.
 
The only place you should have heard the difference is when you hit the peak capacity of an amp. Below that, they should operate the same. If at normal levels they sound different, then there is a different gain or EQ setting happening somewhere.

The peak capacity of an amp isn't always clearly readable on the spec sheets. Yes, the QSC amps can hit 1100 watts, but for how long? Maybe a half cycle at 60 hz? After that it might drop significantly. Not enough power to produce sustained bass at that power. It's still advertised as an 1100 watt amp though, which technically isn't wrong.

Nobody makes a commercial audio amp today that can do full sustained output forever. Generally speaking, your higher end amps will have more reserve power to work with, so you can get somewhat usable sustained output for musical use at their peak power ratings.
 
Brian, as I pointed out I had to lower the sub gain on the processor because of the increased output from the amp. And that wasn't at peak capacity. All I am saying is a number of people on here said the difference would not be audible. It was. I can't explain why,I can just tell you there was quite a difference.
 
If there is audible difference, that is due to processing somewhere, or, as stated earlier, you are hitting the peak of the QSC amps and not realizing it.

The QSC amps sound absolutely horrid on a long thin power cable. Give them a very stiff power supply, and it's a night and day different amp. It's noticeable well before you see the clip lights doing anything.
 
Top Bottom