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power amp review

Discussion in 'Amps and Cabs [BG]' started by inazone, Oct 15, 2003.


  1. inazone

    inazone

    Apr 20, 2003
    Colorado
    I have 4 power amps and was going to get rid of 2 of them so I did an A/B test to see which ones I have the most use for. The amps are qsc 3402, qsc 1602, stewart 1.2 and a crest vs900. I used a modulus q5 with bart pu and aguilar pre, ashdown rpm1 evoII pre amp into a bergantino 322. I used one side of the amps at 4ohms. 3402 1100 watts 2 rack 21 lbs, 1602 500 watts 2 rack 21 lbs, crest 450 watts 3 rack arround 40-50 lbs, stewart 1.2 350 watts 1 rack 11 lbs. The winner was, well it depends on what your looking for. The crest sounded the best, a big difference. It had a much richer and fuller sound. Much better lows and crisper highs. The 1602 came in second. The stewart was a little to clean with the modulus. As far as volume the 3402 was loudest followed by the crest. Believe it or not, there isnt that much volume difference in all the amps. The 1100 watts has the headroom I need but I could get by with the 350 watts. All in all it depends on what you want. For the best sound, crest. For my gig rig, 3402. For studio or quiet amp use (like with upright bass) stewart 1.2. The qsc 1602 would be second choice in all the above wich maybe first for overall. btw, the fan in the 1602 is MUCH quieter than in the 3402. Even in idle. This is just my opinion, good luck.
     
  2. I also found the Stewart to be a tiny bit crisper than the PLX, but not by much.
     
  3. 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
    You didn't mention anything about matching the gains of the amps you compared. That's important, because the one that's set louder will win, even if it's actually identical to the others.
     
  4. inazone

    inazone

    Apr 20, 2003
    Colorado
    I had the gains up all the way on each amp. Thats how I play live, gain up, pre amp eq flat and make the adjustments from the bass. btw, Im keeping the two qsc plx amps. They have the features, power and size to fit my needs. Great amps!
     
  5. 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
    Because you didn't match the gains, that in itself would account for some amps sounding better, crisper, richer, etc., than others.

    If you want to compare sound quality of different amps, you really have to match their gains, not just set the gain controls to the same positions.
     
  6. inazone

    inazone

    Apr 20, 2003
    Colorado
    very true, I just tested them for fun, set them how I would use them in my bass rig. I also had the 30hz filter on in the qsc's. The thing that got me was with the volume. I thought there would be a bigger difference in the amps than there was. On the other hand, the headroom difference was huge.
     
  7. vanselus

    vanselus

    Sep 20, 2000
    Boulder, CO
    None

    In a way it's still a fair general comparison though, if the test is "which sounds best at the volume you normally play" instead of technically what each poweramp sounds like in general. It is definitely a point to consider though, and our perception of any sound changes dramatically with the changes in volume...
     
  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
    But he was essentially testing them at different volumes, because their gain structures varied among the different models.

    From a psychoacoustic perspective, human hearing is such that if you take two perfectly identical sound systems and simply make one slightly louder than the other, that louder one will sound fuller, with better bass, etc.
     
  9. vanselus

    vanselus

    Sep 20, 2000
    Boulder, CO
    None

    Both points noted, and I agree - in terms of raw technical comparison. But isn't there going to be differences in the perceived volume in real-world playing (ie. gigs) also? So the comparison, while skewed, is sonically fair... Or are you saying that the main tonal difference between the amps is volume, that when adjusted for gain structure, they would sound almost identical?
     
  10. 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
    Listening at different volumes will skew the perceived sound quality. That is only "sonically fair" if you don't care about comparing sound quality. But if one is going to announce that something sounds better than something else and attribute it to the product rather than the difference in volume, I have to point out that the conclusion is inherently faulty.

    There is no perfect amplifier, but well-designed amps are more nearly perfect than less well-designed ones, and as such will sound very close to identical (and often will sound indistinguishable from one another) when compared fairly.
     
  11. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    That's what he's saying. Good power amps sound so similar that to do any sort of tone comparison it's essential to have them producing exactly the same volume. Back in the days when I was chasing the holy grail of hifi-dom (futile!) I noticed that the magazines took great care to ensure that all the equipment was set up to exactly the same loudness by using test tones and SPL meters, otherwise the loudest amp/source/speakers would always win.

    Alex
     
  12. 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
    I should clarify what I wrote to point out that the amp's or system's tone doesn't change with volume, but the way the human ear perceives it does.

    The sensitivity of the human ear to bass frequencies in particular varies wildly with sound pressure level, while at midrange and upper mids it is far more uniform.
     
  13. redneck2wild

    redneck2wild

    Nov 27, 2002
    Memphis, TN
    I saw a study that showed that perceived Bass frequencies of test subjects' hearing were less sensitive at lower sound levels as compared to midrange frequencies but the gap flattens out as the sound level increases.

    Bob, does this sound correct?
    Or have I been conned by marketing hype again?
     
  14. 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, you're correct. The same thing happens but less pronouncedly at the very high frequencies, too.

    This phenomenon was first documented by Fletcher and Munson, two researchers at Bell Laboratories, in about the 1920s or 30s. Here's a good place to learn more: http://www.sfu.ca/sonic-studio/handbook/Equal_Loudness_Contours.html.