What characteristics make up a good amp?

Discussion in 'Archived Threads 2001-2004' started by Kevin. W, Feb 27, 2002.

  1. Kevin. W

    Kevin. W Screenwriter

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    You see all these technical terms of Torroidal, Output Devices, uF power storage, etc. What I'm curious off, is the minimum requirements for an Amp to be good at what it does.

    Kevin
     
  2. Jeff D.

    Jeff D. Supporting Actor

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    Kevin:
    A smart man will all but ignore the tech-side of amps. You can get too caught up in numbers. Any amp, from a respectable brand, will be suitable for any normal situation (ie. driving a normal load of speakers at normal listening levels). If you have special requirements (ie. a difficult load, or play things at extremely high levels etc.), then you should pay a bit more attention to the specs.
    Rather, listen to the potential candidates. In-home trials are always nice, as they allow you to audition in your system and room context. Different amps have different sounds, some which will complement your system, others which will not. Also, don't assume you can't tell the differences. I hear that so often and yet, working in an A/V store, I see almost daily a revelation as someone hears a difference they never expected to. THEN the fun begins. [​IMG]
    /Jeff
     
  3. Kevin. W

    Kevin. W Screenwriter

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    Thanks Jeff for the info. But all that aside. What size a torroidal, what size/type of caps, number/size of output devices would you say is needed to power a normal Hometheater.

    Kevin
     
  4. Jeff D.

    Jeff D. Supporting Actor

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  5. Kevin T

    Kevin T Screenwriter

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    i've always thought of amps that can double their output into 4 ohms and again into 2 ohms are good. however, there aren't a whole lot out there than can do that and those that can are pricey.

    kevin t
     
  6. ling_w

    ling_w Second Unit

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    Torridial transformer, uF capacitor & number of output transistors usually just tells you how capable this amp is in delivering its rated power. It doesn't tell you much about how the amp would sound.

    Some thing that might go into a good sounding amp would be no capacitor in its signal path, film capacitor in rest of audio circuitry, film bypass cap for power supply, metal film resistors, no global feedback, low local feedback, fully differential amplification stage, teflon boards, tightly regulated power supply with multiple taps for different stage, fully hard wired, etc.

    Of course, all that would not matter if it is of inferior design. That is why you got designers that makes good stuff no matter what price range (like John Curl, who designed multi-thousand Vendetta Research products to low budget brands like Parasound.)
     
  7. Charles Ledbetter

    Charles Ledbetter Auditioning

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    Jeff put it quite nicely. Ignore specs, for the most part. You see so many people get all caught up in THD specs. That has very little to do with how good an amp sounds.

    What you have to be careful to avoid is amps that just can't do what they're claiming in the specs. I've run across them before: They'll claim like 500 watts per channel and the cost will be $300. Sorry, it just can't be done. What they do is drive the amp into a 1/4 ohm load and measure the power output right before the amp bursts into flames. Yep, 500 watts alright. Has nothing to do with any kind of real world application.

    Like Jeff said, look for a REPUTABLE manufacturer. I'm not going to make any specific recommendations because it'll just ignite another holy war here. Scan through the posts. You'll see the names that pop up all the time.

    Charles
     
  8. John Doran

    John Doran Screenwriter

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    Jeff,
     
  9. Larry B

    Larry B Screenwriter

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    John:

    I agree with most of your comments, and compliment you on how well you described your position. I do however, have one question about your statement

     
  10. John Doran

    John Doran Screenwriter

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    larry,

    when i was talking about "sound" as being important, i was speaking of those acoustic qualities like "warmth", "coolness", "analyticity", "being laid-back", "being open", "darkness", "richness", and so on. basically, all of the non-quantifiable aspects of an amplifier's performance.

    i was trying to say that there could well be an amplifier that had the "warmth" and "richness" i liked, as well as the provision of an extensive soundstage, BUT that lacked the OTHER structural characteristics vital for the other aspects of sound reproduction, like transient response, or depth and control of the low-end.

    if an amp is as mellow as i like, but can't keep up with die hard or epsiode 1, then i don't want it.

    if an amp kicks the crap out of me during gladiator and saving private ryan, but makes my music sound like it was played by a computer, then i don't want IT, either.

    you know?

    - jd
     
  11. Jagan Seshadri

    Jagan Seshadri Supporting Actor

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    ***SLIGHTLY OFF-TOPIC***

    John Doran,

    Before the server crash happened, did you read my comments to you about negative feedback, and did you find them useful?

    -JNS
     
  12. John Doran

    John Doran Screenwriter

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    jagan,
    i'm afraid i can't remember your comments on negative feedback specifically, but i did find most of the replies useful, so i'm sure you have had something to do with whatever insight i now have.
    if you remember what it was you posted, please feel free to do so again - i certainly don't mind learning valuable lessons more than once.
    take care,
    - jd
     
  13. BruceD

    BruceD Screenwriter

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    Three basic qualities I look for in a power amp:

    1) High peak current ability (for low efficiency speakers)

    2) High slew rate (for transient response)

    3) High damping factor (for good bass control)
     
  14. Jeff D.

    Jeff D. Supporting Actor

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    I don't really know what to say to that. I guess the best I can without being insulting is, what a shame.
    /Jeff
     
  15. John Doran

    John Doran Screenwriter

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    jeff,
    this is what you said in your post:
     
  16. Jeff D.

    Jeff D. Supporting Actor

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    Poor bass response, muddied transients...these aren't necessary evils of the physical design characteristics. I've heard amps that have plenty of guts on paper but sound positively weak.
    Also, poor bass response and muddied transients...if this is what you were referring to in your original post, then that is fine. You cannot judge an amp's bass response by numbers alone. These are subjective qualities you will hear when you audition the amp.
    If, however, you audition an amp and love its sound from top to bottom, but refuse to buy it because it only has 100 watts when everyone else has 125, then that is a shame. [​IMG]
    Numbers on a page will only tell you if that amp can physically drive the speakers you have. Nothing more or less. Those numbers tell you nothing about sound quality. You can put all the power you want behind an amp, but if the overall design, from start to finish, is not sonically beneficial, what good is all that current and all those watts?
    /Jeff
     
  17. Jagan Seshadri

    Jagan Seshadri Supporting Actor

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    John Doran,
    Jeff Kowerchuk is right about not the numbers not telling the whole story, and I think you agree as well. BruceD's points are good ones, as are ling_w's points.
    I always look at the innards of audio equipment before I buy it. I have found a good place for this has been SMR Group's Component Image Library. The heft and size of power supply components is not a total indicator of perfomance expectation, but it does indicate what league of amplifier you're getting.
    From an engineering perspective, overdesign and oversizing of components is a good idea. For example, if the main amplifier is only meant to run at X Watts then it's fine to design the supply to run at 4X Watts comfortably, but a 1.5X design would suffice. Considering that, there's no compelling reason to spend money on grossly overdesigned products.
    As for power requirements of audio systems, match it to the size of your listening room. Big rooms need big power, small rooms need far less, and if you have a powered subwoofer doing your bass-frequency work, then your main amplifier can be smaller still.
    By the way, here is a article on toroidal versus EI-frame transformers in audio that may be of interest to you.
    -JNS
     
  18. Jeff D.

    Jeff D. Supporting Actor

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    A good example of numbers not telling the whole story is NAD amps.
    Historically, NAD has been very conservative in its power ratings. I had an old 304 integrated, that was rated at 30 watts per channel. When the unit was reviewed, however, it was discovered to give more like 60 watts per channel (continuous). That may not sound like much (though many are surprised to learn that, continuously, we use very little power, even at higher levels), but what really surprised was its 180 watts of dynamic power. Holy mutha! [​IMG] You would never guess it just by looking inside its demure chassis.
    NAD has always focused on quality over quantity. Even if you look at their power ratings for their HT receivers today, you'd probably dismiss them in favour of brands that claim 120 wpc or whatever. NADs 60 wpc ratings seem small, but if you combine that with a healthy dose of current for peak demand, and kick-ass sonics, you've got an HT receiver than can give the big boys a run for their money.
    /Jeff
     
  19. BruceD

    BruceD Screenwriter

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    Jeff,
    That's why current not wpc is more important to enable that headroom.
    I never judge an amp by it's watts rating.
     
  20. John Doran

    John Doran Screenwriter

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    jeff,
    i couldn't agree more that numbers don't tell the whole story. but i think they tell part of the story.
    like i said in my original post, i would only buy an amp that sounded good and had other properties - lots of power, high slew rate, good damping factor, high-quality components, etc.
    thanks for the thoughtful responses. [​IMG]
    regards,
    - jd
     

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