• 11-08-2008, 06:32 PM
    musicman1999
    class d amps with jmlabs speakers
    hi guys

    i know we have gone over class d amps before but i am looking at a new rotel class d amp to mate with my jm labs speakers and i was curious if anyone had done so already and if so how it worked out. the rotel is a 1575 and my labs are cobalts and pre-pro is anthem.

    thanks
    bill
  • 11-09-2008, 06:24 PM
    Mr Peabody
    Hi Bill, I've heard great things about the Rotel Class D, unfortunately I have not heard one yet. There seems to be a growing unfounded negativity toward digital amps. As you know there are more classes of digital than just "D". My Linn is digital, Class V, it drives my Dyn's just fine. Any issues I have with sound quality is inherent to the amp itself. My Linn is 5x125 watts and weighs in at a whopping 11 lbs. I have yet to run out of power. People can no longer stereotype these types of amps, there are good and bad as in any other amp technology. If digital is done correctly it can have great results.

    One of the guys on the board had his Pioneer receiver hooked to an Accurus amp, I asked him if he had ever tried the internal digital amps. After asking him he became curious and gave them a try. He now uses the internal amps.

    A Rotel dealer shouldn't have a problem with a demo, I say give it a spin.
  • 11-09-2008, 08:56 PM
    canuckle
    Rotel's Class D offerings are brilliant. I've used them and thus far haven't met the speaker that is too much for them. Soundwise and powerwise, they are at the top of my serious power-system recommendation list.
  • 11-10-2008, 06:28 PM
    musicman1999
    Thanks for the feedback guys, i have always had the idea that class d amps are bright sounding, where i got this idea i do not know. If true this would be a concern because Labs are of a bright sounding nature and get along best with warm sounding gear.

    bill
  • 11-12-2008, 10:16 PM
    canuckle
    You get that idea from the audiophile hooey that gets thrown around without any solid, factual basis. If one amp sounds different from another such that you can abx the difference reliably, then one amp is broken. The whole point of an amp is that it amplifies a signal without distortion over a wide frequency range. It's not rocket science and so long as the speaker's impedance isn't overwhelming the power supply, then every amp on the market today can do it within the same specs. Numerous challenges have been posed and well-documented on the internet where people are offered large sums of money if they can tell one working, level-matched amp from another. Nobody has ever won any money, because it can't be done.
  • 11-13-2008, 01:09 AM
    blackraven
    Canuckle I agree with a little about what you say. But I got to audition a Van Alstine Tube amp against my Parasound Halo A21 and my Adcom. The Parasound and the Van Alstine had the same power rating for all practicle purposes (500wpc and 400wpc respectively and the Adcom was 260wpc). Using the same preamp, speakers and CDP, the Van Alstine Amp was noticeably warmer. And the Parasound has more transparency then the VA and sounded much better than the Adcom. There were differences in warmth, bass transparency and detail between all three amps. I did a blind in home test at Frank Van Alstines home and in my home with the wife and my 17 and 21y/o kids and we were all able to tell the difference between the amps. I use to think that all amps pretty much sounded the same and many do sound the same, but a lot don't. Also your peripheral equipment has to be up to speed. A poor quality source and cheap speakers can certainly mask differences in amps and preamps.
  • 11-13-2008, 07:00 AM
    Mr Peabody
    I think most on the board have switched amps in and out of their exact system enough to realize that amps can be as different as any other component. Various size, or strength in power supplies, the reserve bank, quality of parts, and especially frequency response are all things that can make a difference. Not to mention tube vs. solid state vs digital.

    Although the basic idea of solid state amps haven't changed a great deal over the decades except for a few designs and improvement in quality of available parts, for example toroidal transformers and capacitor materials. The digital amp is a different story all together. It may be considered "rocket science". You should read the history sometime. Digital was not a new idea, I can't remember the decade it was tried, failed and shelved. Digital is prone to massive distortion in the higher frequencies, that's why they made their come back first in subwoofers and took years before the technology was tried again. It took a lot of work to get a digital amp to sound good enough to compete with a quality solid state amp. The harsh high end was a trait of early generation digital amps but today there are a few that have reached the point where they are quite good.

    My Linn amp is not to the point of causing fatigue or offense but the highs are crisp and the extreme low end could use a bit more control. This is fine for HT but not my choice for music. I've had the ARC digital amp in my system and did not care for the sound but I don't think anyone could tell it was a digital amp by it's sonic signature. I've heard T+A amps with digital switching and they are excellent sounding amps by any standard. The T+A compared to higher priced Krell were even better on speed and control. I preferred the Krell's high end and Krell drove difficult speaker loads to higher volumes where the T+A went into protection. So one would have to weigh the price difference over the advantages. The point of the extraneous commentary is to point out further differences that can be heard and displayed.

    Others here are better versed on DBT's but I've read their responses enough to know not to put stock in the results.

    Those who might claim all amps, or any other component, sounds the same will change their mind once or if further experience with equipment comes about.
  • 11-13-2008, 08:50 PM
    canuckle
    I'll only make some quick comments because it's all been done so much before.

    Reading:

    ABXes

    More ABXes

    Beyond everyone's anecdotal "using the force" observations of how listening to different systems "made them feel," there is no scientific study that proves it is so. Anywhere. Ever. Reference one... anywhere (Steve Hoffman's forum of magical ears isn't science, btw). As you'll note in the tests, tubes can indeed be picked out on occasion. That is because tubes are defective from an amplification point of view. They cannot amplify a signal in a flat-line, full-frequency, distortion-free kind of way. You may like it and that's great - enjoy, many people do. But it's distorted and unnatural. Defective really.

    Mr. Peabody, I'm familiar with the history of class D amps... familiar enough to know that calling them digital amps displays a complete lack of knowledge about how they work. We're not talking about whether poorly designed, crap-spec'd equipment from ages past can compete with properly designed equipment. Your history lesson should also teach you that the ICEpower class-D design has eliminated all of the problems you allude to.
  • 11-13-2008, 09:18 PM
    blackraven
    So I guess my wife and kids must be from the Star Wars Universe when they consistently picked my Parasound amp over my adcom in a blind AB test. I think I'll change my sig to Darth Vader.

    Yes, the tube sound is due to distortion, but I would not call it any more unnatural than the Solid State sound. The bottom line is that there is nothing in the world today that can reproduce the sound of live music. Its all a matter of preference. I prefer Van Alstine Hybrid Tube/SS gear over the pure tube sound. I've heard a lot of tube gear with too much bloom and a lot of high end SS gear that sounds too clinical. What I do find is that alot of tube or hybrid gear sounds more liquid for lack of a better term.

    As for Class-D amps, I do believe they are the future. Light weight, little heat and less parts. They should be cheaper too, but the manufacturers will continue to rape the consumer of high end equipment because they can.
  • 11-14-2008, 05:39 AM
    Feanor
    Give it a rest
    Quote:

    Originally Posted by canuckle
    I'll only make some quick comments because it's all been done so much before.

    Reading:

    ABXes

    More ABXes

    Beyond everyone's anecdotal "using the force" observations of how listening to different systems "made them feel," there is no scientific study that proves it is so. Anywhere. Ever. Reference one... anywhere (Steve Hoffman's forum of magical ears isn't science, btw). As you'll note in the tests, tubes can indeed be picked out on occasion. That is because tubes are defective from an amplification point of view. They cannot amplify a signal in a flat-line, full-frequency, distortion-free kind of way. You may like it and that's great - enjoy, many people do. But it's distorted and unnatural. Defective really.

    ...

    First, we should understand about DBTs that they cannot prove that there are no differences in sound between components. They can only prove that there are differences or that differences cannot be heard under the conditions of the test with the test subjects in question.

    At various times DBTs, such as the ABX tests you refer to, have proven that differences exist between certain components. One cannot dismiss these results simply on the basis that tube amplification is "defective". This certainly not the case depending on the depending on the design and topology used; it is acknowledged as I recall, that tubes are inherently more linear voltage amplifiers than transistors. Many transistor designs are only low distortion with lots of negative feedback which produces higher, and odd order distortion products. There is evidence that tubes' slightly higher but low, even order distortion is less deleterious to human sound enjoyment than the transistor distortions.

    People here who have read many of my posts know I am not a person who makes extravagant claims about my hearing. Time and again I have dismissed as non-existent or irrelevant the small differences among, for example, cables. But I almost always here differences between amplifiers in extended listening, and I will point out that these differences have often been contrary to my expectation so I feel the arguement that I hear what I expect to hear is not valid.
  • 11-14-2008, 11:11 PM
    canuckle
    Quote:

    Originally Posted by Feanor
    First, we should understand about DBTs that they cannot prove that there are no differences in sound between components. They can only prove that there are differences or that differences cannot be heard under the conditions of the test with the test subjects in question.

    You need to study up on the difference between a dbt and an abx. Abx tests do in fact prove the lack of any difference. That's why they are the preferred tests for these situations. Though it's certainly not uncommon to hear this typical line about "they can only test for things that people can hear but there are other magical things that cannot be detected in any measurable way in the universe that make my $3000/ft cables a million times better sounding."