Is this valid information or bs?

[kaapong]

Thanks Ray

So how exactly does the amplifier rated. Do they actually measure power output at specific impendence or do they just take it form the quoted transister spec. Heck, do they even use the same method between different maker ??

Come to think of it, a plot of power output vs impendence might be useful... (or better, current vs voltage vs impendence, but that would make one hell of a graph to look at. )

[boa12]

k, that's what i've learned to look for in a good amp.

the relation of power output at different load impedances. if an amp is rated at 200W @ 4ohms & 100W at 8ohms then that implies better current producing power than one rated at 150W @ 4ohms & 100W at 8 ohms.

sorry what i meant above was that say w/ the one doing

150W @ 4ohms the current is not compensating in relation to the voltage as well as the 200W @ 4ohms, all other things being equal.

somebody in home theater was just asking about a panasonic receiver rated 100W at 6 ohms. but they don't provide any other output ratings at other impedances, say like 8ohms. imo that's just deceptive as they can up it some w/ 6ohms figure. though at 8ohms it's probably still around 80W give/take some.

also other things to beware of they use the 100W 6ohms at 1khz instead of the more preferred 20-20khz range. they do give a 100W rating from 40-20khz but slide in that's only with stereo (2 channels driven).

so an ideal would be like an amp that's 200W at 4ohms,

100W at 8ohms, 20-20khz, all channels driven.

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My Home Systems Page

[ahhbee78]

moon,

FYI there's a place down in salem called 'hear no evil' and they have been great to me. im not sure if they're still a klipsch dealer (my cousin told me they were dropping them) but they are the only high-end store in the greater salem area and possibly better than most places in portland. i cant remember what brands of amps they carry, i just bought speakers there, but i really enjoyed dealing with them.

they'll also trick out your car if you want... even neon!!!!

------------------

Denon 1601

Sony VCR, DVD, CD Changer (all from Best Buy... that means its the 'Best')

Philips CD Burner

Panasonic 32" TV

KSB 3.1

KSC-C1

KSF-S5

KSW-12

[JohnA]

I can't stand it ANY MORE! "HIGH CURRENT AMP" IS NOTHING MORE THAN ADVERTISING!

Of COURSE H-K is blowing smoke and BAD! If both receivers are putting 75 watts into any load, speaker or not, the current output from each one is *exactly* the same! It doesn't matter that the H-K could produce more current than it takes to put 75 watts into your speaker. The Denon would be capable of putting even more current into that same speaker because it is designed to put out 47% more power!

Ray is right. Speakers are not constant impedance loads. So, an amp that has the power supply reserves to maintain constant voltage into a varying impedance will operate without audible strain (distortions and/or non-linear frequency response) and will probably sound better WHEN PUSHED NEAR ITS MAX OUTPUT. However, if a 75 watt amp is averaging 0.05 watts and hitting microsecond peaks of 20 watts (typical Klipsch operating range), its power supply will never be challenged even if it were to be a "low current" amp.

Power=current x current x impedance.

So, for any 2 amps producing the same power into the same impedance, regardless where you measure it or what it is, the current must be the same.

Looking at the AVR 520's specs, it is not a "high current amp. It cannot drive all channels to the same output as it can just 2. Its power supply is not large enough. The hallmark of so called high current amps is at least 1.5 times the 8 ohm rating into 4 ohms (2 times is theoretically perfect). H-K doesn't even spec 4 ohm performance.

Rant off.

From looking at each receiver, I'd bet on the Denon sounding better. Neither will be pushed driving Klipsch.

John

[m00n]

Hmmm. Any retort on John Albright's comments? I am all ears.

------------------

the m00n system

RF-3II Front floors

RC-3II Center

RS-3II Surrounds

RSW-12 Subwoofer

Harman Kardon AVR 520

Toshiba SD 3205 DVD

Samsung 27" Flatscreen

c>Microsoft XBOXc>

f>

[HDBRbuilder]

I still love my old HK 900+...(ducking here)

[boa12]

"If both receivers are putting 75 watts into any load, speaker or not, the current output from each one is *exactly* the same!"

john, why not say volts are also exactly the same across all amps at any given wattage output? - volts would have to be constant for that to be true.

are you saying the proportion of current and volts is always the same for all amps at any given wattage output & a given load?

anyway, the point i was trying to make is for different loads (such as those speakers present) different amps produce different amounts of current in proportion with volts. if the load goes up & you get higher wattage output, then it comes from current. if the load goes up the same & you get even more wattage output, then it comes from even more current. or are all the audio gurus i'm reading wrong? that's all i got. gave up hands-on electronics class after high school.

haven't looked at the denon vs hk specs. but if the hk

does, just f.e., 75W at 8ohms & 120W at 4ohms & the denon does 80W at 8ohms & 110W at 4 ohms, then i'd say the hk puts out more current when needed. again this is just an example.

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My Home Systems Page

[boa12]

oh & back to the big picture. moon i've got my 1st receiver - a sony de935 that's 110WX5 @ 8 ohms. it has higher watts. chuck that hk at 1/2 your cost & i'll sell you this to replace it.

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My Home Systems Page

[Ray Garrison]

John,

If you're talking levels of 100dB or less, and you're talking about Klipsch speakers, and you're using a few watts or less, yep, "high current" capability is only good for some marketing fluff.

If you have difficult speakers, and you're playing as loud as you can play without driving your amps into hard clipping, an amp that is not constrained by limited current capability is going to play up to it's ultimate output limit with less frequency related artifacts than an amp that has less ultimate current output.

The La Scalas I enjoyed so much were, from my own admittedly subjective and uncontrolled observations, not an easy load to drive. Up to (and this I DID measure) 110 to 112 dB or so, just about any amp I tried sounded pretty much the same. But, put on the William Tell Overture and crank it to 120+ dB on the peaks, and some amps just wimped out totally on the bass drum. For reasons I have yet to understand, my little Rotel RA850 BX2 integrated amp, which is only rated at like 30 watts or something, sounded better than anything else I'd tried. Go figure.

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Music is art

Audio is engineering

Ray's Music System

[m00n]

quote:

---

Originally posted by boa12:

oh & back to the big picture. moon i've got my 1st receiver - a sony de935 that's 110WX5 @ 8 ohms. it has higher watts. chuck that hk at 1/2 your cost & i'll sell you this to replace it.

---

Hmmm let me think about that for a sec.......

Nope.

------------------

the m00n system

RF-3II Front floors

RC-3II Center

RS-3II Surrounds

RSW-12 Subwoofer

Harman Kardon AVR 520

Toshiba SD 3205 DVD

Samsung 27" Flatscreen

c>Microsoft XBOXc>

f>

[boa12]

ray, i'm sure on the current production at different loads but not so sure on another preconception i have (the one john dwelled & nailed me on ).

i thought amps as in their transformers, capacitors had

different efficiencies. so though the 120V input is constant but dif amps have those dif characteristics that make for different proportions of voltage & current. or at any given load impedance & power ouput,

are voltage & current exactly the same.

fe, if an hk & denon both are doing 75W at 8ohms, volts

& amps will always be exactly the same?

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My Home Systems Page

[J M O N]

Yes, If you have two different amps, feeding identical speakers the same amount of power, then the current they are pushing is exactly the same.

But that doesn't mean that all amps are identical. If you are using low impedance speakers (there are some out there with very low nominal impedance), or the speakers impedance dips very low at certain frequencies, then higher currents are needed from the amp. Some amps are capable of delivering these higher currents, some are not. This is the reason some amps are rated for driving 2 Ohm nomimal impedance speakers, and others you don't want to use with anything less than 8 Ohm speakers.

If you are using nominal 8 Ohm speakers and the impedance doesn't dip very much (and, you are not connecting more than on pair in parallel), then the current issue is not likely going to be a problem. Most of your "high-end" superamps (Krell, Bryston, etc.) are capable of putting out huge amounts of current for the purpose of driving low efficiency, low impedance speakers (e.g. electrostatics). HK's claims are not just marketing ploys, it really can be advantageous to have that extra current in SOME applications.

[m00n]

Well all I know is that the H/K sounds good to me. Seems to have pleanty of umph to push my klipchers. That makes me happy.

Could use a bit more crunchy sound, and would like to have 7 powered channels like the equivelent Denon, but I think this H/K will do me justice for a while. Once THX really starts kicking into full swing on DVD's I just may upgrade to the HK AVR 8000. drool.

------------------

the m00n system

RF-3II Front floors

RC-3II Center

RS-3II Surrounds

RSW-12 Subwoofer

Harman Kardon AVR 520

Toshiba SD 3205 DVD

Samsung 27" Flatscreen

c>Microsoft XBOXc>

f>

[boa12]

thanks jmon. i guess i should be spanked by doctor ohm

for implying some amps are high voltage & others are high current.

guess what i was thinking is that with higher loads the

better amps give a higher current proportional to the voltage than an amp that gives less current in proportion to the voltage.

but of course if an amp is rated higher at a lower impedance then it puts out more current when that's needed. trouble is especially on receivers you can't get the real power reserve capability because they don't give them to you or really mess w/ the rating standards. can't believe kh doesn't give a 4 ohm rating when they claim the high current, f.e.

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My Home Systems Page

[T2K]

With your speakers and the multitude of options that it offers,you shoulda got the 3802. The lower current sounds "warmer".

Keith

[m00n]

quote:

---

Originally posted by talktoKeith:

With your speakers and the multitude of options that it offers,you shoulda got the 3802. The lower current sounds "warmer".

Keith

---

Oh, well thats a good reason for me NOT to go with Denon. I want bright. Actually I have been told that the Denon was a bright sounding receiver.

------------------

the m00n system

RF-3II Front floors

RC-3II Center

RS-3II Surrounds

RSW-12 Subwoofer

Harman Kardon AVR 520

Toshiba SD 3205 DVD

Samsung 27" Flatscreen

c>Microsoft XBOXc>

f>

[JohnA]

john, why not say volts are also exactly the same across all amps at any given wattage

output? - volts would have to be constant for that to be true.

are you saying the proportion of current and volts is always the same for all amps at any

given wattage output & a given load?

As a matter of fact I am. Power = Volts x current, also. So, for 75 watts every amp must apply the same voltage and current to the same impedance, what ever it is.

I chose to focus on current because that was the subject of the question. I also focused on a constant impedance load since we are discussing the performance of 2 receivers connected to the same set of speakers. What ever the capability of an amp into another impedance, the 2 hooked to the same speakers will put out the same voltage and current at the same wattage, up to the limits of the amps power supply or protection circuits, if it has any.

I've also focused on the operating envelope we will typically see with Klipsch rather than discussing what an amp might see with another brand, say Magnepan. If we throw in too many variables, too soon, understanding will excape all of us. There WILL be speakers that tax the entire amp and show weaknesses that Klipsch will not.

IF I were made King, I'd require an amp to double its 8 ohm power output at clipping into 4 ohms at clipping in order to use the label "high current".

Ray, a La Scala is undoubtedly a tough load. The min. should be about 3.5 ohms at 50 and the max. hits 40 or so at 2200. I'll bet there is not a wider range anywhere. I'll also bet the autoformer causes a substantial phase shift between voltage and current. That's gotta be strange for the amp.

None of this precludes an amp from sounding good in your setup. Tube amps rarely, if ever increase power output into 4 ohms.

John

This message has been edited by John Albright on 04-26-2002 at 11:52 AM

[boa12]

john, but you seem to be discounting the idea that 2 different amps at the same rated output driving the same set of speakers will exhibit different characteristics at different loads like you already agreed above speakers do have on various material.

iow, if a pipe organ cranks on a set of cornwalls it'll

present a loads below at times 8ohms to the amp and that amp may have more current reserve to handle it better. ohm's law aside that's what i was implying & think anybody with hk was implying.

i agree it is some hype on the part of hk as it's a receiver without a 6 or 4omh rating to begin with. but it's not total bs for the reasons above.

i don't care which one is better because i don't own either. i agree with you though as far as the receiver war here that the denon probably has higher output at 4ohms than the hk anyway. though neither would be good for driving a 4ohm load for an extended period of time anyway.

but I think we both know power amps at the same 8ohm output rating sound different, especially on the lower frequencies.

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My Home Systems Page

[Ray Garrison]

John,

Thought you'd find this interesting. "Difficult load" is relative... a La Scala might not be the easiest load ever seen, but imagine the poor amp trying to drive this thing:

That's the impedence and phase of the Linn Komri, their new super-duper high end speaker. Here's what John Atkinson had to say about it in Stereophile this month (April 2002):

"I estimated the Komri's voltage sensitivity to be just under 87dB(B)/2.83V/m. This was both to specification and right in the center of the range I have encountered in my measurements. The Komri, however, is a relatively difficult load for an amplifier to drive. Fig.1 shows how its impedance magnitude and phase change with frequency. First, the magnitude drops below 3 ohms above 3.5kHz, reaching a minimum value of 1.7 ohms at 10.9kHz. This in itself will demand a lot of current from the amplifier with music that has appreciable high-treble content.

But look also at the dotted trace in this graph. This is the electrical phase angle, and it reaches quite a large value in two regions. The first, in the middle bass and below, is due to the crossover between the Komri's passive upper-frequency and powered-woofer sections. In general this angle will be benign, as the passive drivers will experience very little drive signal in the affected band. But the phase angle still becomes fairly extreme in the crossover region, where the speaker will be handling large input voltages. At 107Hz, for example, a lowish impedance magnitude of 3.67 ohms coincides with a capacitive phase angle of 54 degrees. The situation is similar in the low treble, where there is a combination of 54 degrees phase angle and 3.6 ohms at 3.14kHz."

That's a real ***** of a load to drive.

------------------

Music is art

Audio is engineering

Ray's Music System

[JohnA]

Boa,

"john, but you seem to be discounting the idea that 2 different amps at the same rated

output driving the same set of speakers will exhibit different characteristics at different

loads like you already agreed above speakers do have on various material."

Not rated output, but *actual* output. While all speakers vary in impedance with frequency, in this discussions we need to hold some things constant so that true statements may be made. At this point, we're discussing conceptual amplifiers driving any speaker. If we confine the discussion to conceptual amps driving one speaker, say a Cornwall, then we can make accurate statements about amp design and behavior as they comply with Ohm's Law. In addition, we also have to stipulate that neither amp is to be driven beyond its capability.

A good comparison might be the old B&K M-200 Sonata I used to have. It was rated at 200 watts into 8 ohms, 385 watts into 4 ohms and stable down to .75 ohms and rated to produce at least 200 watts at .75 ohms. Compare that to the H-K, rated at 75 watts into 8. When driving the Cornwall at the same power level (within the H-K's capability), the 2 amps will produce the same voltage and current. That fact that the M-200 *could* flow 16.3 amps at .75 ohms and the H-K can't doesn't matter, the Cornwall doesn't dip that low. Its impedance is high enough that it will prevent the M-200 from delivering that much current and the drive voltage that results in less than 75 watts cannot push more current than that that results in 75 watts, or 20 or whatever level we decide to test at.

Ray,

That Linn does look like a bear!

John