Does the weight of a power amp affect the sound?

Discussion in 'Amps and Cabs [BG]' started by PolkaHero, Jul 15, 2003.

  1. PolkaHero


    Jan 5, 2002
    My bandleader is trying to tell me that you have to have a heavy power amp to produce exceptional bass frequencies. He says a heavy Crown Macrotech(I think) is the only way to go.

    What about you guys here that use the QSC PLX series? How does the sound of these lightweight amps compare to much heavier power amps?

    I don't think it makes much difference. Please help me to settle this dispute. Thanks!
  2. Mcrelly


    Jun 16, 2003
    Minnesota, USA
    that might have been true 10 or more years ago, but with new computer driven designs they are getting more and more out of less and less see yamaha cp200 or EA iamp 800 for examples
  3. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    Yes, never take an amp less than 100 lbs to a gig. :D

    Seriously, with so many different types of desigs now weight all by itself won't tell you much about the amp. Best thing to do is listen to any amp before you buy it.
  4. JJBluegrasser

    JJBluegrasser Wannabe Snazzy Dresser

    Apr 17, 2003
    USA, Raleigh, NC
    I use a QSC PLX1202 and I love it. Lightweight, and I think it sounds better than the RMX series. I'm also an electrical engineer, and I'm fairly certain that weight does not have to equal power. Technology only gets better over time.

  5. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    In the "old days" more weight meant bigger (and better) transformers, aka more power and headroom.

    But "digital" amps don't fall under that rule.
  6. PolkaHero


    Jan 5, 2002
    I'm not talking so much about power output as I am about sound quality. He says that lighter power amps produce a "mushier" sound than heavier amps.

    Thanks for the replies!
  7. adouglas


    Jun 23, 2003
    Bridgeport, CT
    Tell him that you'll buy his argument if HE carries the amp.

    Preamps have a whole lot more to do with quality of sound than power amps do, n'est-ce pas?
  8. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Your bandleader ought to talk to some knowledgeable people. ;)

    Here's your chance to become more knowledgeable than your bandleader. Look at what a lot of sound companies use for sub and bass frequencies. In recent years, more and more of them are using high-quality lightweight amps for this purpose. Look at what many bass players are using, and you'll see a similar trend.

    Your bandleader is probably thinking of back in the 80's and early 90's, when lightweight amps were generally designed with light weight as the prime goal and allowed for performance compromises to reach that goal. Back then, few audio amp designers were really up to speed on switching power supply technology, so they didn't come up with designs that were really suited to audio power amps. These days, designers can shoot for performance improvements that well-designed switching power supplies can offer.
  9. chucko58


    Jan 17, 2002
    Silicon Valley, CA, USA
    I paid for all my gear myself. Well, me and MasterCard.
    Bob's right, the weight of an amp is not at all related to the sound quality. Of course his employer builds both lightweight and heavy (conventional) amps; but they make more money off the lightweight ones. ;)

    With conventional power supply technology, there's actually some truth to the weight myth. Big low end power requires a stout power supply, and that means lots of iron and copper in the power transformer.

    But that rule doesn't apply to switch mode power supplies. They're more complex than the traditional supplies, to be sure, but it's a worthwhile tradeoff for getting rid of that boat anchor of a transformer. And switchers can provide constant output power, no matter what the line voltage does. That's not possible with a traditional supply.

    Class D, Class T, and other variations on the "digital" amp also reduce weight by minimizing wasted power in the output stage. But heat sinks are aluminum and not as heavy as iron and copper, so digital amps don't save as much weight as a switching power supply. Digital amps are still a bit finicky too.

    Of course, you can combine both technologies for an even greater weight savings.
  10. jokerjkny


    Jan 19, 2002
    NY / NJ / PA
    lol! that's my motto for my whole rig! ;)

    but if my Peavey DPC or Stewart 1.2 is any indication, the answer is a resounding NO! :D
  12. Petebass


    Dec 22, 2002
    QLD Australia
    (Begin rant) So how long before people start to realise that same applies to lightweight speaker cabs. As Bob says, if it's engineered right, the sound isn't compromised (end rant).
  13. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas

    With modern digital and switching power supply designs, weight should not be considered as a positive clue towards the resultant sound quality.

    With more conventional designs, to produce solid, powerful bass sound a large, heavy power supply definitely helps, but is still not a quarantee of good sound quality.
  14. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    The Republic of Texas
    I'll have to hear it to believe it.

    Here's my reason for saying this: bass frequencies create alot of vibrations (including the cabinet itself--try sitting on top a bass cab while playing at live performance levels). Ideally, you want only the drivers and the air to vibrate. The more the cabinet vibrates the more acoustic energy is being robbed from the notes produced by the drivers and the less solid and distinct the notes will sound. The heavier the cab, the less prone it is to vibrations.
    If you use a lighter material, unless you bolt it down to the floor or put something VERY heavy on top of it to keep it from vibrating, the cabinet itself will be in-a-sense sucking bass from the drivers.

    [Put a powerful 15" bass driver in a 1/8" plywood box and watch it boogie across the floor. Of course, an exaggeration, but makes my point.]
  15. Petebass


    Dec 22, 2002
    QLD Australia
    Wel at least you're prepared to have a listen before writing them off.

    Oh and that cab you described - that's not withing my definition of "engineered correctly" :)
  16. I can't say I agree that a heavey amp sounds better, but I know for sure that I like the heavier amps better. I have used the PLX3402s for my sub woofers in my PA and for the bass cabs in my rig, they sounded all right in both apps but my Crest CA12's have much more power and head room and I personally think they are more musical. The 3402's sounded great at a low to mid volume but they totally pooped out with the high volumes.

    Now, I am a loud player and a loud soundman but it always seemed right when the PLX's started to sound really good and would hit hard they would shut down from not enough current, so I put in larger breakers (went from 20A to 40A breakers) that helped but then it would just do a thermal shut down. My crest's have never done that with the exception of blowing a breaker from full on clipping. I really did like the PLX's because of the weight and size but for the same money I have to have a unit that will always work 100%.

    Now most of you fellow bass players don't play at 115+db constant so they may work great for you but this has been my experience with the digital switching amps.
  17. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    No, that shutdown would be from the AC voltage sagging to below about 85 volts for longer than a few cycles. Were you running a lot of stuff on extension cords?
  18. No, when I was really pushing them they were normally on a 25' 12/3 extension running straight into a 20 amp breaker on my 200 amp distro. Once I installed the 40 amps that problem would stop and then i would push them into thermal over loads. Both problems happened with subs and mids in either 4 or 2 ohm loads with 2-4 speakers per channel. I did have the low voltage happen in a few bars but normally it seemed to be current draw. You could always tell when it was going to happen. It would sound great and then just ween out until everything returned or cooled off and then boom power again, much like kinking a garden hose and then fixing it. Oddly as soon as I went to the heavy Crests it ceased to exist unless I just go into full on clip.
  19. Only when traveling over water.