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Is there a sonic difference between solid state amps?

Discussion in 'Amps and Cabs [BG]' started by ivanthetrble, Dec 31, 2004.

  1. ivanthetrble


    Sep 9, 2002
    I think everyone will agree that there are differences in the tone of tube pre-amps vs solid state pre-amps and I think the SS vs Tube amp thing has really been covered as well. What about solid state power amps? Do you think there is a significant difference in the tone produced by different solid state amps? If you had two SS power amps hooked to the same pre-amp, the same cab, with both amps putting out the same wattage that you could do an A/B comparision would you be able to hear differences between the two? Whadda think?
  2. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    Some people would say yes. Having been in that situation I'm more inclined to say that the difference, assuming relatively equal price points, is insignificant and totally insignificant by the time you're in the mix of a band.
  3. the dude

    the dude Supporting Member

    Sep 19, 2004
    My experience is the answer is "Yes, there is a major difference!"

    I did a recent A/B with a Stewart 2.1 and a Crest CA9 - same bass and preamp with same settings.

    Much to my surprise - completely different tones.
  4. IvanMike

    IvanMike Player Characters fear me... Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    yes sometimes they sound different. do they sound as different as a tube power section vs a solid state section? i dunno. It depends upon the amp. I think that the "good"/(generally expensive and recognized) amps tend to all sound "good", but even then, there are tonal differences. However, i still belive that your preamp and speakers will have a bigger impact on your tone than a solid state power amp will.

    now this is something we (and guitar players) don't take into account as much as we should. There are mind blowing tonal changes, and there are subtle ones. Most tonal differences between all kinds of equipment tend to be on the subtle side and get lost in a band mix. Does this mean we should stop searching for a tone we like? No. But it does mean that there are much better things to do than agonize over a particular preamp or cabinet or what have you. I used to have an eden, an swr, an alembic, and a demeter. You know who knew which one i was using as a preamp? Me. And sometimes i was wrong, forgetting that I'd switched from one to the other between sets or during practice. :p
  5. ivanthetrble


    Sep 9, 2002
    Different in what ways?
  6. the dude

    the dude Supporting Member

    Sep 19, 2004
    I would say the Stewart is probably more even tonally. I would liken it's tone to maybe that of an iAmp. A very good tone to be sure.

    The CA9 on the other hand has more weight - I'm talking about sound here, although it is also the heavier of the two amps. You could say "more balls," but that is such an overused term - although in the ballpark (no pun intended) of what I hear. The CA9 sounds bigger, and to my ear has a more "complex pallette."

    The caveat - both amps are used, but seem to work and sound good.
    (Speakers for comparison were Bergantino, bass was Fender Precision.)
  7. Fuzzbass

    Fuzzbass P5 with overdrive Gold Supporting Member

    Solid state amps that use MOSFETs are supposed to sound more tubelike than non-MOSFET ss amps. That seemed to be true with the MOSvalve 500 I used for awhile.
  8. the dude

    the dude Supporting Member

    Sep 19, 2004
    Very interesting. I was about to say that the CA9 sounded a lot more like a tube amp - but thought that would be too much of a stretch. Guess it wasn't.
  9. Bongolation


    Nov 9, 2001
    No Bogus Endorsements
    That's Ampeg's whole schtick. How true it is I don't know, but it's how they justify the oxymoronic solid-state SVTs; it may no longer be be "Super Valve Technology," but "Sortta Valvelike Tone" I suppose. :D
  10. IIRC It can be true, but the way the amp is built has to be closer to what tube amps use as well, but more often than not it isn't done that way.
  11. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    Is there a real difference between a power amp with big heavey iron transformers and the lightweight power switching amps?? I had an RMX1850HD and a PLX2402 and I thought the RMX sound was, I don't know.....denser. It was probably just my imagination. Some engineer here on the forum has the technical background to answer this one. I know the RMX in the Ampeg wooden rack case gave me a pain in the groin that still bothers me if I lift something.
  12. morebass!

    morebass! I'm all ears Supporting Member

    May 31, 2002
    Madison WI
    FYI back a few years,probably about 1998, Bass Player did a shoot out of power amps using the same bass, preamp and cabinets for all. I think Tommy Shannon was on the cover. They came to the conclusion that there were differences and described them. Crest was similarly described as above. I don't think they thought that it was as powerful a difference as basses or cabinets though, but we all know that.
  13. Well here's a thread that's gone around more than a few times before. In the interest of debate and controversy :D here are some points that haven't been covered here yet. We all know (myself included) that there are some small differences in the sound and behaviour of power amps from different manufacturers. Why do so many engineers believe that they shouldn't be all that different?

    The first point that comes out is that the input voltages must be correctly matched, especially if you are comparing amps. This has a large effect on the performance of a given amplifier and resultantly on how it sounds to your ear. Folks who state that they "compared power amps using the same preamp, settings and bass" should be looking more closely at whether they matched the power amp input requirements properly, otherwise they have invalidated any comparison. Louder will always sound better to your ear, and an amp that is not properly input-matched will rarely be the louder one.

    The second point that directly relates is one of design consideration. Granted this is a bass-related thread and not "pro audio", but shouldn't a SS power-amp essentially be the proverbial "straight wire with gain"? Shouldn't the hands+bass+pickup into preamp (for adjustment) merely be amplified by the power amplifier, contributing as little as possible to the overall sound? Of course this would not be true of tube amps as stated earlier in the thread.

    Many years ago I discussed these subjects with Henry Kloss, Dr. Amar Bose and Dr. Floyd Toole while participating in NRC listening tests. The largest effect on overall sound was of course determined by the input (hands+bass) and output (speakers). Very few people (if any) could pick out different SS power amps of similar design that were properly matched in double-blind tests in an anechoic chamber. I think Bob Lee has posted some very good information on this over the past year.

    Of course there is a whole audio industry built on these nearly-imperceptible differences. Your thoughts? :bag:
  14. I just did a quick check on specifications to underline what I've posted above...

    Crest CA-9 input sensitivity = 0.775 volt
    Stewart World 2.1 input sensitivity = 1.0 volt
    QSC PLX3002 input sensitivity = 1.7 volt

    Of course, not all specified measurements are taken in exactly the same way, but you can see a bit of a pattern emerging, especially when folks talk about which amps "sound better"...
    Remember that the louder amp will always sound better to your ear.
  15. the dude

    the dude Supporting Member

    Sep 19, 2004
    ...and having said that, it doesn't matter if the Stewart 2.1 is turned up louder, the CA9 still has more "umph" to my ears...
  16. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    DFW, Texas
    Don't you mean the output voltages must be matched?

    If three amps are all fed the same input voltage and they have different input sensitivities, won't the output levels be different?

    You probably meant something different than how I interpreted it.
  17. IvanMike

    IvanMike Player Characters fear me... Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    that was the "Play The Blues!" issue from around september of 1997. There's also an article called "loud Enough?" in the same issue by a little known writer :D
  18. Schwinn


    Dec 4, 2002
    Sarasota, FL
    Wow! I had those 2 exact amps side by side and I could hear a difference too. Can't describe it now because it was a long time ago and I just did a couple minutes of testing. I don't think it was your imagination.
  19. ivanthetrble


    Sep 9, 2002
    I also looked a the specs on the Stewart and QSC websites and found that the input sensitivity in the QSC PLX line gets larger at you go up the model line;

    PLX 1202 1.0/ 0.9
    PLX 1602 1.2/ 1.1
    PLX 2402 1.5/ 1.3
    PLX 3002 1.7/ 1.5
    PLX 3402 1.9/ 1.7

    The Stewart is listed at 1Vrms but I didn't see any note about the impedence. So explain this to me like I'm an idiot, (not that big of a stretch :meh: ) if you have two amps and amp A has an input sensitivity of 1.0 and and B has a sensitivity of 1.5 and you hook them both to the same pre-amp then amp A will appear louder? Dos this also mean that as you go up the ladder in the PLX amp line that they will appear louder or less loud, or neither? I also notice the gain numbers between the QSC 3002 and the Stewart World 2.1 amps. The QSC is listed at 40x gain or 32dB where the Stewart is rated at 66x or 36.4dB. IIRC the smallest change in volume you can hear is about 3dB so you would be able to tell that the Stewart,even though it is a less powerful amp than the QSC 3002, would appear louder or at least would have the potential to be louder? Jeez, this is all to much for my brain on the morning of New Years Day. :eyebrow:
  20. Fuzzbass

    Fuzzbass P5 with overdrive Gold Supporting Member

    Well, some here discuss (anecdotally) blind listening tests, the result of which was that modern quality power amps are equally transparent regardless of type or brand. That said, some people I highly respect say they can hear the difference between lightweight and heavyweight power amps.

    Me and my bad back are sticking with my lightweight Stew regardless... sounds great to my ears. But I have a hard time believing that there isn't some sort of tradeoff associated with lightweight amps.