Why all amps and receivers aren't the same.

Discussion in 'AV Receivers' started by Seth=L, Sep 25, 2006.

  1. Seth=L

    Seth=L Screenwriter

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    I don't know if this is relevant, or if this thread will even stay open, but I am going to give this a shot anyway.

    So you might ask yourself, what difference is there between my Kenwood 600 watt receiver and his H/K 225 watt receiver. The difference is truth in ratings. The FCC doesn't regulate these things closely enough, maybe they don't have the resources anymore, who knows. So many audio manufacturers bloat their power ratings with a little cunning, or they just straight up lie. Some of you may have seen the white van scams before, those guys are straight up lying. Not much of their specs are real, they quite literally pull numbers, numbers that look good, out of thin air.

    Many factors can be looked at when considering a new receiver or amplifier. One of the most popular is reading user reviews or maybe specifications. Just know that what you read isn't nearly as usefull as listening to something for yourself. People have different listening needs. An individual likes to listen to heavy metal probably won't have a very usefull review for someone who listens to classical and jazz. Not to say reviews are bad, they deffinitely are usefull to find reliability and maybe erganomics.

    Things to be aware of when looking at amplifier or receiver amplifier performance specs:

    The wattage: I will show you a bad example of a power rating.
    110 watts RMS per channel 6 ohms (1khz at 0.7 THD)

    Then a good one:

    95 watts RMS per channel, all channels driven 8 ohms (20hz-20khz at 0.06 THD)

    The problems with the first rating are:
    The (1khz), this is the frequency that they tested the amplifier's power, This single frequency is not a difficult one to produce. A more accurate rating will tell that it is able to provide that amount of power at any given frequency between 20hz (being the lowest and most demanding frequency to reproduce) and 20khz (the highest average frequency audible to humans).

    Another thing to look at is the load impedance. Some of these specs aren't offered in great detail for many manufacturers. They should have the wattage ratings for each impedance(resistance to electron flow), measured in ohms. If the ratings for the 8 ohms vs. the 4ohms are higher then make sure your speakers don't have lower ohms before buying many budget brands, lower ohms means more resistance.

    Another important factor is continuous output and all channels driven. These manufacturers are very carefull in how they word things. If the specs say something like this [100 watts per channel RMS] that could mean that the receiver is theoretically capable of delivering 100 watts RMS on just one channel, were the RMS of all the channels together may be in the neigborhood of 20 watts RMS. A rating like this [100 watts RMS, all 5 channels driven] would indicate the amp is capable of delivering 100 watts of power RMS to each channel at the same time.

    One very simple way to evaluate most receivers and amps without listening to them to find what they are really packing is size of parts (weight), power consumption, and some internal #'s. Not all these methods will always work. Manufacturers have found many ways to make things more eco-friendly. Digital amplifiers operate very efficiently. They run cooler than analog amps, and weigh much less. They have their short comings and upsides as well. Some have boomy bass and reticent highs.

    Large power supplies (transformers), large capacitors (round can shaped objects) and hefty discrete output stages (transistors) are all characteristics of a quality amp. If the caps are the size of a spool of thread, the transformer the size of a rubix cube, and a couple large transistors might get moderate performance in a receiver. Though a transformer that weighs 10 pounds, and caps as big as pill bottles, and lots of transistors on a nice heatsink might indicate a more powerfull amplifier

    Anyone feel free to add your opinions, and correct possible mistakes. I really hope that this can help someone in the quest to buy a receiver or amplifier.
     
  2. FeisalK

    FeisalK Screenwriter

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  3. Arthur S

    Arthur S Cinematographer

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    Seth

    I have a Kenwood reciever, which one do you have? Or were you just using that as an example?

    Thanks
     
  4. Seth=L

    Seth=L Screenwriter

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    Example, many of the lower end Kenwood, Sony, Pioneer, even Yamaha, Denon and Onkyo do this sometimes, they use some very misleading power ratings. It is less common for H/K or Outlaw to boast power they don't realistically have.
     
  5. Seth=L

    Seth=L Screenwriter

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    Those are very good articles. I would recomend anyone looking for a new amp or receiver read those articles. Thank you, FeisalK.
     
  6. Seth=L

    Seth=L Screenwriter

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    For music listeners, true RMS power is important. If one listens to heavy metal at very high volume, then they would likely want some true rated power. With home theater we may not need that continuous power.

    An example of how skewed the ratings are. I have a Carver AV-505 5 channel amplifier. It is rated at 80 watts RMS per channel all channels driven 8 ohms from 20hz-20khz at 0.08THD. The amp weighs 42 pounds. It has an oversized power supply, modular design, and caps the size of small aerasol cans. I had a Onkyo TX-DS787 THX Select receiver rated at 100 watts RMS 8 ohms (20hz-20khz at no more than 0.08THD). It weighed 36.6 pounds.

    Now I am not saying the Onkyo TX-DS787 is a bad receiver, I am just saying it's power ratings are less than true. Note the Onkyo has a six channel amp versus the 5 channel Carver, so not only is the power divided amongst more channels in the Onkyo, it has numerous other factors weighing against it's truth in power. Input power is 440 watts, where as the Carver can draw up to 900 watts. The Onkyo weighs almost 10 pounds short of the Carver, which the Carver is exclusively an amplifier. The Power supply is smaller in the Onkyo,as are the Capacitors, and the output stages.

    While 80 watts doesn't seem like much, it really is on the Carver. It makes the THX certified Onkyo's 100 watts, tuck it's tail between it's legs and run home to it's mommy. I also had at one time a Kenwood power amp that was rated at 150 watts rms, the Carver still smokes even that.

    Funny thing is, you can get Carver amplifiers for so cheap now, because the company doesn't really exist anymore, Bob has moved on to bigger and better things since Carver.
     
  7. FeisalK

    FeisalK Screenwriter

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    I think the most important thing about those articles is that the 100W per channel is a marketer's concoction; audiophiles the world over live with tube amps that put out 10 or 20 watts per channel; one of the best sounding amps I've heard in recent times was a Tripath powered Charlize putting out only 10W at 4Ω. Power is overrated (pun intended) sometimes [​IMG]

    and besides, is there such a thing as true RMS watts?

    also, I read recently on TI that they only need to test for 1/8th peak power draw to be certified for a power consumption rating; so if an amp can draw 100W per channel peak, it can be rated as 12.5W per channel active power consumption; it does make sense in a way because there is never a program (music or movies) that will draw 100W in all channels all the time.

    All this averaging out helps the marketing people stretch the power output rating [​IMG]
     
  8. Arthur S

    Arthur S Cinematographer

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    Seth

    I have both a Kenwood receiver that test benched at 92 watts X 6 with all channels driven simultaneously, and a 70 pound Citation 7.1, rated at 425 watts X 2. Power draw on the Citation is 2500 watts max. The difference in sound quality is minimal.
     
  9. JeremyErwin

    JeremyErwin Producer

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    Want to maximize the power rating? Specify a 6-ohm load or less. My Onkyo TX-SR502 has a 3-ohm rating.

    Dynamic Power: 160 W, 3 Ohm. (The more rational claim is 75W, 8 Ohm, 20Hz--20kHz).

    However, despite the claims about WRAT, and High Current, Low Impedence loads, another section of the manual warns against connecting low impedence speakers.

    Maybe the dynamic power is meant for those "8-ohm speakers" that actually bottom out at...

    ...consults manual...

    3.0 ohm.

    They sound pretty good to me...
     
  10. Seth=L

    Seth=L Screenwriter

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    Dynamic power is a fancy pants way of saying peak power, extremely short term based. I think one of the articles said 100 milliseconds, that isn't very long. There are a lot of movies that have scenes with intense demands that last much longer than that.

    I once owned the 502, I thought it was great for the money. I had fans on mine to keep the heat and clipping to a minimum, and to increase power output. I found it to be very affective to use the fans, though if you do that be sure the fans are quiet and I would have a voltage regulator.
     
  11. Seth=L

    Seth=L Screenwriter

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    Some may not notice a distinct or worthwhile advantage. Different people have a different ear when it comes to these things. It can also depend on the speakers being used. Lets consider the Kenwood has 100 watts RMS per channel in stereo operation. The Citation has 425 watts x 2. Two identical pairs of speakers with [email protected] are connected to both amps and in some way or another are fead the same material. The speakers would achieve close to 102db assuming they haven't reached their power handling with the Kenwood, that is fairly loud. With the Citation, considering the speakers limit of power handling has not been reached could achieve close to 108db. Six decibels is quite a difference.

    I can understand someone not noticing a huge difference without pushing the envelope. But I would certainly think that modest volumes the Citation sounds better because it is a better amplifier. As FeisalK said, there are tube amplifiers that sound many times better but have much lower wattage output. The main thing to consider when looking at amplifiers is how they sound, how well they pair with your speakers. As I said before, I had a Kenwood amp once, it was powerful but sounded bright and I found the amp to be unlistenable. That isn't to say all Kenwood amps have the same sound, certainly they have changed their sound since the 80's, which is where the Kenwood amp was from.
     
  12. JeremyErwin

    JeremyErwin Producer

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    Well, I rarely can get away with turning it above "40", although occasionally I venture into the 50s. The test tones read at 75db, somewhere in the mid to upper 50s. So, I'm not quite "cranking" it.
     
  13. Seth=L

    Seth=L Screenwriter

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    If you have efficient speakers, you can get a lot out of just 20-30 watts. If you have more demanding speakers then you need more power. But if you never really "crank it" then maybe you don't need 200 watts rms. If you wan't quality amplifier sound and know what you are doing then tube amplifiers are perfect. They require lots of upkeep and they are very delicate, just as well their sound is very delicate.

    I would like to add don't pay much attension to THD (Total Harmonic Distortion) ratings, tube amplifiers have very high THD's comparied to transistor amplifiers. If you just decide to not buy an amp because it has 3%THD then you could be missing out.
     
  14. Chu Gai

    Chu Gai Lead Actor

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    No FR, channel separation, graphs of the spectral distortion profile on the Charlize....Sheesh. No offence, but what a garish looking thing. You could just as easily pick up a car system for around the same money and get AM/FM and also run it off a 12 volt wal-wart.

    Bragging about 10 watts is like Pam Anderson bragging about that she's reduced her breast size to A-.
     
  15. JeremyErwin

    JeremyErwin Producer

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    apropos to that-- I have a pair of Grado headphones, and I've (briefly) thought about getting a dedicated amp for them. One of the amps I've considered is the Creek OBH-11.

    The OBH-11 can be ordered with two different wallwarts-- one is cheap and the other is relatively expensive. From what I've heard, the base power supply is very noisy, and an upgrade to something else is well worth the money (relatively speaking, of course).

    Here's the problem. The Sonic-T doesn't have a built in power supply, and from what I recall, it's a separate option. Buy a cruddy wallwart, get noise. Buy a good one, and be noise free.

    Most amplifier discussions seem to come down to the power supply. It's advanced as the reason why htibs can't pass a all-channels driven test. It's advanced as the reason why receivers do poorly with a 2-ohm load.

    Here's a "review" from that "we don't publish negative reviews" website. Note that the reviewer is using 93 db/W single driver loudspeakers.

    I suppose if you have highly sensitive 4-ohm loudspeakers, don't listen to loud music, and can procure a good power supply, the amplifier might be a interesting choice. But, otherwise, no. It certainly won't power these.




    btw, Stereophile will be reviewing the "high end" version in October.
     
  16. Seth=L

    Seth=L Screenwriter

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    You underestimate the tube amplifiers. The difference between 10 watts and 100 isn't as great as you would think. Say you pair those Klipsch corner speakers with a 10 watt tube amplifier, and some PSB's connected to a 100 watt amplifier. You may get the same or more out of the tube and Klipsch just because of efficiency. Klipsch aren't hard to drive, and pairing them with a quality tube amp will really smooth them out. I wouldn't, however recomend PSB/tube combo, PSB speakers are to power hungry.
     
  17. Arthur S

    Arthur S Cinematographer

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    And neither is the difference between 92 watts and 425 watts. With virtually everyone recommending that all speakers be set to Small, and bass redirected to the subwoofer, amp demands are far less than they used to be before subwoofers were ubiquitous.

    The sound of amps is an endlessly debated subject on which honest people disagree. From my reading, perhaps one person in 10 is a golden ear, and can beat 50/50 consistently. For the vast majority of people, in double blind testing, they cannot detect the difference between a $200 receiver and a $2,000 power amp.

    There are all kinds of generalizations floating around about which receivers sound "warm", which sound "bright", and as you get into more esoteric mags, like Stereophile, things get truly ridiculous, with terms such as "pace", "rhythm", and other silly terms.

    In my experience, the only way to really spot the differences is by having the various receivers at home, in your system, and swapping them out. That is how I found out that Nakamichi makes some of the best sounding amplification available. I don't consider myself a golden ear, but I could hear the harmonic correctness of the Nak, that made real instruments sound more natural. Other receivers have more slam. No one product excels in every area, so you pick your compromises.

    Finally, I have found that 92 db average level, is very, very loud. So, 102 db vs. 108 db is academic.
     
  18. JeremyErwin

    JeremyErwin Producer

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    that's the thing. Average SPL isn't peak spl. Consider the ubiquitous "reference level" for the cinema (and, perhaps for home theater): 85 db. That doesn't mean that the peaks are at 85 dB. Oh no. It means that the main channel peaks are 105 db, and the LFE is producing 115 db, peak.

    Insane, perhaps. But it's those peaks (not to mention the room itself) that necessitate a large amplifier.
     
  19. Seth=L

    Seth=L Screenwriter

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    For those who don't have the option to set their speaker to small, like me. When dealing with stereo only rigs, which I realize that isn't home theater, you generally don't have bass management anyway. If you have small speakers and a small receiver, no doubt you should set the speakers to small. If you have larger full range speakers and a seperate amp, why not allow the speakers do what they were designed to do. If I had Martin Logan or Thiel speakers they wouldn't be set to small. I wouldn't even set my PSB's to small. The only limitations they ever had was the amplifiers powering them. The Onkyo receivers would clip, so at that time they were set to small. With larger amp I don't see the need to set them to small, they sound better at full range anyway, and since clipping is no longer an issue, why not.
     
  20. Seth=L

    Seth=L Screenwriter

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    I want to hear the crescendo, and believe that I really heard one.
     

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