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Discussion Starter · #1 ·
Would you say that one of the key techniques to make a high current amplifier/receiver is lowering the rail voltage? In other words, trading off voltage for current.


So your amp/receiver might now measure worse into 8 ohm than your competitors, but you start to look better when you measure to 4 ohms.


Of course, your heat sinking and components have to be up to to the task of handling more current.


This would explain why Harmon Kardon receivers have had low 8 ohm power ratings over the years.
 

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That is a possiblilty, but what does HK gain by listing a better 4 ohm power spec, when they tell consumers not to use 4 ohm speakers with their products? HK receivers have lower power specs, because HK has historically been more honest with their power ratings. A look at Sound & Vision magazines tests over the last 20 years attest to it.
 

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Discussion Starter · #3 ·
But what do you mean by honest? When I look at benchmarks, the rated power of the amps seems to generally agree with the rating. The FTC rule seems to allow for a loose definition of the term associated channels, so other manufacturer's ratings can't be directly compared to HKs All Channels Driven.


Ignoring AV amps for a moment, even their stereo amps had less power per dollar when I looked at them years ago. They could certainly be rating their receivers at a lower part of the output distortion curve which would give them lower ratings. Perhaps that's what you mean by more honest?
 

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What benchmarks? The FTCs rules allow exaggerated claims based upon consumers perceptions. All channels driven is assumed and therefore should be the benchmark. Sound & Vision Magazine has printed the inconsistency of many AVRs power ratings, tested vs advertised. HK's AVRs have power rating that are much more consistent with tested, all channels driven power rating. So are NAD, Rotel, Cambridge Audio, Arcam, Etc.


Regarding any particular manufacturer, its anyones guess, but HK rating power based upon lower distortion levels is the likely answer. It has been rumored that Krell Full Power Balanced amps tested higher in 8 ohms than listed in their specs for the purpose of printing the power doubling down into 2 ohms.
 

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Discussion Starter · #5 ·
I agree the FTC rules are misleading. As for whether manufacturers are being dishonest for exploiting them, I guess I could understand someone taking that position. We could debate it, but the problem of not being able to effectively compare power ratings would go away.


I admit I am curious as to why HK bucks the system, so to speak. Maybe the marketers don't run their company. Maybe there's someone in charge who has put their foot down and determined they will take a stand when it comes to how power ratings are determined.
 

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Quote:
I admit I am curious as to why HK bucks the system, so to speak.

I don't know for sure where it's from but it is sure one hell of a good marketting move if you asked me. For years I've had to scratch my head and shrug my shoulders when asked about what does it mean "high current amp". This is from someone who should know these things but all I can come up with is something dumb like: maybe it can put lots of current into the speakers??? Then walk away quietly wondering how this is different from a high power amp, is it class A, AB, D what?


It's different and mysterious because no one except HK or whoever sells it even knows what they are talking about. I have to admit it does sound pretty cool whatever it is. If I didn't know any better I might even fall for that...
 

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"We could debate it, but the problem of not being able to effectively compare power ratings would go away."


Comparing AVRs power specs is about as useless as comparing contrast ratios for HDTVs. I do believe amplifier power is the most important factor in choosing an AVR. DTS HD-MA or Audyssey EQ isn't very impressive when the amp section is clipping.


Harman International isn't a japanese company, so HK isn't bucking the system. European and American Hifi manufacturers have always marketed products that offered lower watts/dollar compared with japanese electronics.
 

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Discussion Starter · #8 ·

Quote:
Originally Posted by Ugly1 /forum/post/17011783


I don't know for sure where it's from but it is sure one hell of a good marketting move if you asked me. For years I've had to scratch my head and shrug my shoulders when asked about what does it mean "high current amp". This is from someone who should know these things but all I can come up with is something dumb like: maybe it can put lots of current into the speakers??? Then walk away quietly wondering how this is different from a high power amp, is it class A, AB, D what?


It's different and mysterious because no one except HK or whoever sells it even knows what they are talking about. I have to admit it does sound pretty cool whatever it is. If I didn't know any better I might even fall for that...

Salespeople love to mention that HK has high current receivers.


Some also try to explain to me how there are voltage watts and current watts. I think that's a distortion of how electronics works, but it is true that you can get the same watt figure along a continuum of voltage/current number.


10 volts @ 10 amps is 100 wats. So is 5 volts @ 20 amps. But it's not as simple as saying give me more amps and less volts to get the same effect because gee, I want current watts not voltage watts.


Say you took a transformer that stepped down 120 volts to 2 volts. And it could supply a lot of current without failing. And you used that to power your amplifier. However, you can't ever amplify a signal to more than 2 volts. The amplifier will not be able to supply enough power to the speakers even though it can draw a lot of current, in theory.


So there's a limit to how much current you can use even if everything in the amplifier can handle it.


If on the other hand, your transformer could output 100 volts, but was limited to 1 amp of output, you would not be able to power an 8 ohm speaker. It would be a bit like shorting a battery. You could hook a 9 volt battery to a 1 ohm load, but it won't output 9 amps. Voltage will drop substantially.
 

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Quote:
Originally Posted by MichaelJHuman /forum/post/17011990


Some also try to explain to me how there are voltage watts and current watts.

Haha! I can only just imagine. Maybe it would be fun for me to go have a chat with one of these sales guys some time for some laughs. I suppose these guys would then go on to say I Watts not equal to V Watts? lol! Here would be a good one to try: ask the sales person if it is I W or V W that is in units of Joules per second and then ask what the units of the other kind of Watts are. Good times. It may be that HK ends up selling tons of stuff in a effective but ethically questionable marketting move and certain class of sales guys squelch any doubts of the existence of the sleaze which sometimes makes the streotypes seem appropriate.
 

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Quote:
Originally Posted by MichaelJHuman /forum/post/17011990


Salespeople love to mention that HK has high current receivers.


Some also try to explain to me how there are voltage watts and current watts. I think that's a distortion of how electronics works, but it is true that you can get the same watt figure along a continuum of voltage/current number.


10 volts @ 10 amps is 100 wats. So is 5 volts @ 20 amps. But it's not as simple as saying give me more amps and less volts to get the same effect because gee, I want current watts not voltage watts.


Say you took a transformer that stepped down 120 volts to 2 volts. And it could supply a lot of current without failing. And you used that to power your amplifier. However, you can't ever amplify a signal to more than 2 volts. The amplifier will not be able to supply enough power to the speakers even though it can draw a lot of current, in theory.


So there's a limit to how much current you can use even if everything in the amplifier can handle it.


If on the other hand, your transformer could output 100 volts, but was limited to 1 amp of output, you would not be able to power an 8 ohm speaker. It would be a bit like shorting a battery. You could hook a 9 volt battery to a 1 ohm load, but it won't output 9 amps. Voltage will drop substantially.

MICHAEL..


You are heading the rite direction..

Except you have failed to mention the variable of time..
How long can the AVR's amplifier sustain putting out the higher demanded voltage/current?

5 Nanoseconds..

100 uS....

100 mS....


Think about voltage as peak level and current as the ability to keep it going..


It starts with the loudspeaker load & sensitivity, room size and dynamics of the source material plus what gain (level) the amplifier is set @. The typical Japanese brands design their power supplies to support a test condition of 2-Channels driven, whereas HK on the other hand design for all channels driven. Additionally pricepoint enters here as well, the lower AVRs trade off power supply capability due to cost pressures.


Another view that some users may not be fully aware of is that Harman has 2 major loudspeaker brands in the consumer space, JBL and Infinity and the HK products are frequently sold with these as systems. The JBL products tend to be port design, to be 8 Ohms with have high sensitivity, the Infinity products are the opposite sealed enclosures, to be 4 Ohms with low sensitivity. So the HK AVRs need to be able to drive loudspeakers of both brands...


The HK AVRs are not designed/built to be the lowest price. HK uses the more expensive, heavy-duty power transformers and thats why they weigh more than the competition. Also note an engineer can design 2 different cost/grade power transformers yet both put out the same voltage. For example, the amplifier could require a voltage rail of +/- 50V, by using lower cost, thinner guage copper wire the power transformer's cost can lowered significantly but still puts out 50V. Compared to another higher cost/grade power transformer that puts out 50V would with heavier guage copper wire. The lower cost power transformer when pushed will heat up much faster, drop in efficiency and its output voltage will decrease. The HK AVRs power supplies are designed similar to those of dediciated component power amplifiers.


No free rides here..


Constant voltage and high current capability are not cheap..


Just my $0.015...
 

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No one is questioning whether or not the HK stacks up to its competition. The question is why can't they just state their performance claims in common English rather than confuse the issue by trying to invent some new language in this suspicious manner which doesn't bring anything useful to the table? It would be different in my mind if they had isolated some new and important audio quality parameter not already being sufficiently covered by existing terminology or if they had invented some novel and new amplifier technology. That just doesn't appear to be the case here. It appears they would just like to make some sales by confusing the issue.
 

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Absolutely Ugly1. People need companies that speak the truth in plain and simple ways.

Like this...

 

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Quote:
Originally Posted by afrogt /forum/post/17015351


How about the competitors stop rating their receivers at 120 watts at 1khz? How valuable is that info?

At least if the conditions are stated which the measurement happens you know what they are talking about. In the face of no testing standard being common in the industry what is an honest manufacturer who creates gear to do other than throw out the measured numbers and the test conditions? With no universally applied testing standards we as consumers get to try and run a comparison with the usually too little data given combined with different test conditions results on unknown nonlinear equipment response curves. Not an easy task if even possible. There is no doubt that this current "system" is easy pickins with some clever wording and enough uneducated consumers.

Quote:
Isn't that a little misleading?

IMO it is only misleading if the context of the test isn't given with the test results. This isn't to say this information makes it easy to make apples to apples comparisons among gear just that I don't think it is necessarily purposefully misleading.


If you want to see how deep this goes try comparing discrete electronics datasheets. For example, there may be 30 ro more manufacturers of 2N3904 npn bjt's but I bet every single data sheet will be full of different numbers. Then when you get equivalent versions all on the bench side by side to compare they all act essentially the same electrically despite the data sheet wording differences.


It can be frustrating and can fool you before you figure out what is happenning. Bottom line is the only real way to make a true comparison is by testing gear yourself minimizing variables and compile the data for a true apples to apples comparisons. There are certainly manufacturers who would welcome a testing standard accepted and used by the industry and still others who would see it as the end of the ability to use confusion to mislead.
 

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Discussion Starter · #16 ·

Quote:
Originally Posted by M Code /forum/post/17014998


...Compared to another higher cost/grade power transformer that puts out 50V would with heavier guage copper wire. The lower cost power transformer when pushed will heat up much faster, drop in efficiency and its output voltage will decrease.

That's interesting. I had not considered the effects of the windings on voltage drop, but it makes sense.


I keep reading, and keep trying to understand the the mysteries ( to me,) of amplifier power supplies. The info you gave is helpful in getting a better picture of transformer performance.


A lot of stuff I read makes assumptions about things without explaining them.


It almost motivates me to purchase some transformers and a bench supply so I can lower the voltage to a safe level, and measure their behavior at speaker impedance and lower.
 

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Quote:
Originally Posted by duvetyne /forum/post/17015071


Think about Ohms law as well, please!

When pulling my quotes and then restating things be sure to show the complete explanation..


I mention voltage and current and then the next line down I mentioned impedance. Those 3 factors make up Ohm's law, however..

Impedance is not just a resistance value..


Also..

Don't fall into the trap of just making a numerical calculation based on a formula that cranks outs values. A loudspeaker is not a resistor, so in the real world an amplifier's actual power output specifications can/will vary significantly from numbers cranked out of a formula..


Just my $0.015..
 

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Quote:
Originally Posted by afrogt /forum/post/17015351


How about the competitors stop rating their receivers at 120 watts at 1khz? How valuable is that info? Isn't that a little misleading?

Yes, a little. Most likely that is a 100 Watt receiver from 20-20k though. So, perhaps a .6dB difference?
 

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Its test results like this that frustrate and irritate people.
http://www.soundandvisionmag.com/rec...-receiver.html


The Sony DG-910 claims 100 watts per channel.

Channel Power Rating : 7.1 Channel Power Rating: 100W x 7 Amp Power (700W) (8 ohms, THD 1.0%)


And then you see the results below. Look at the 5 channel rating?

DOLBY DIGITAL PERFORMANCE


All data were obtained using various test DVDs with 16-bit dithered test signals, which set limits on measured distortion and noise performance. Reference input level is -20 dBFS, and reference output is 1 watt into 8 ohms. Volume setting for reference level was 60. All level trims at zero, and except for subwoofer-related tests, all speakers were set to "large," subwoofer on. All are worst-case figures where applicable.


Output at clipping (1 kHz into 8/4 ohms)

1 channel driven: 84/138 watts (19.2/21.4 dBW)
5 channels driven (8 ohms): 30 watts (14.8 dBW)*

Distortion at 1 watt (THD+N, 1 kHz, 8 or 4 ohms): 0.02%

Noise level (A-weighted): -75.1 dB

Excess noise (with sine tone)

16-bit (EN16): 1.2 dB

Frequency response: 20 Hz to 20 kHz +0, -0.1 dB


*Multichannel tests, regardless of source signal (digital or analog, stereo or multichannel) or decoding modes, caused the STR-DG910 to limit output to about 30 watts or less per channel; see accompanying lab notes. Since the receiver lacks analog multichannel or preamp inputs, direct testing of power-amp channels was not possible.
 
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