Harman Kardon and high current

[BJP]

With HK 635, High Instantaneous Current is +/-50 Amps. Does that mean that high current is only instantaneous or is it constant, but much less than 50? Are HK receivers great all around, or do they just give a good punch during explosions etc? Also does HK have any DSP programs or just Dolby Digital, Pro Logic and DTS?

 

[PENG]

I am not sure if you can find any receiver that can do 50A continuously. First, consider this:

Voltage (V)=Current (I) X Impedance (Z), i.e. V=IZ.

Let's say your 8 or 4-ohm speakers can dip down to 2 ohms momentarily, you will need 100V (I doubt any amp can even come close to this voltage level at its output) to push 50A through that speaker. I think the 635's +/-50A is the total current output, so if you divide it into 5 channels, each channel only have to output 10A into the speaker that it drives. In that case, the amplifier only needs to develop 20V to send 10A through a 2-ohm load, or 60V for a 6 ohm load. That said, I think there is no chance for all 5 speakers to have its impedance dip so low at the same instant.

So if you have an 8-ohm speaker that holds its impedance relatively constant, the 50A capability won't do anything for you.

Secondly, Power (P)=Voltage (V) X Current (I) X power factor, so even at an output voltage of 20V, at 50A

P=20X50=1000W (assuming p.f.=1). In order to output 1000W, the 635 would have to pretty much draw a full 15A from the outlet. That means you would need a dedicated output for the 635 if you want it to be able to push a total of 50A through 5 speakers simultaneously with all 5 speakers having their impedance to dip down to 4 ohms or lower.

On surface, it would appear that HK's high current capability would serve you well if you have low impedance speakers. However, HK receivers are designed for 8-ohm speakers, so what's the point, other than it helps in case your 8-ohm speakers could dip momentarily to 4 ohms or less at certain frequencies.

And yes, according to the HK website, the +/-50A is an instantaneous rating. There is no way the 635 can sustain that kind of current at any length of time, except for "instantaneous", meaning a very short split second (milliseconds, or may be even micro seconds).

 

[Buckeyefan 1]

Great answer, Peng.

You will be hard pressed to find a receiver for the money that surpasses the quality of an HK. www.jr.com usually has some nice deals on the HK's. The AVR7300 is an absolute steal at it's price, but not many can afford the $1350 price tag. The 635 is also a wonderful receiver. You need that punch during explosions, etc... That's when most low to mid end receivers fail. They cannot reproduce the crisp highs and solid bass needed for those split second bursts. The best receivers never seem to get loud because there is little distortion at those higher levels, or "bursts." When I play my Denon at very high levels, it doesn't seem loud, but you cannot carry on a conversation - even in my next room.

 

[mtrycrafts]

I am not sure if you can find any receiver that can do 50A continuously. First, consider this:

Voltage (V)=Current (I) X Impedance (Z), i.e. V=IZ.

Let's say your 8 or 4-ohm speakers can dip down to 2 ohms momentarily, you will need 100V (I doubt any amp can even come close to this voltage level at its output) to push 50A through that speaker. I think the 635's +/-50A is the total current output, so if you divide it into 5 channels, each channel only have to output 10A into the speaker that it drives. In that case, the amplifier only needs to develop 20V to send 10A through a 2-ohm load, or 60V for a 6 ohm load. That said, I think there is no chance for all 5 speakers to have its impedance dip so low at the same instant.

So if you have an 8-ohm speaker that holds its impedance relatively constant, the 50A capability won't do anything for you.

Secondly, Power (P)=Voltage (V) X Current (I) X power factor, so even at an output voltage of 20V, at 50A

P=20X50=1000W (assuming p.f.=1). In order to output 1000W, the 635 would have to pretty much draw a full 15A from the outlet. That means you would need a dedicated output for the 635 if you want it to be able to push a total of 50A through 5 speakers simultaneously with all 5 speakers having their impedance to dip down to 4 ohms or lower.

On surface, it would appear that HK's high current capability would serve you well if you have low impedance speakers. However, HK receivers are designed for 8-ohm speakers, so what's the point, other than it helps in case your 8-ohm speakers could dip momentarily to 4 ohms or less at certain frequencies.

And yes, according to the HK website, the +/-50A is an instantaneous rating. There is no way the 635 can sustain that kind of current at any length of time, except for "instantaneous", meaning a very short split second (mili, or may be even micro seconds).

The other formula - power = IxIxR. 50A squared is 2500 watts not counting R as 1. I seriously doubt it will ever be able to do this even instantaneously Let alone into a speaker load.

I'd like to see their dynamic capability first

 

[mtrycrafts]

With HK 635, High Instantaneous Current is +/-50 Amps. Does that mean that high current is only instantaneous or is it constant, but much less than 50? Are HK receivers great all around, or do they just give a good punch during explosions etc? Also does HK have any DSP programs or just Dolby Digital, Pro Logic and DTS?

I think that claim of 50A is meaningless. That amp will never put out at least 2500 watts instantaneously. In their dreams perhaps.

 

[RLA]

I think that claim of 50A is meaningless. That amp will never put out at least 2500 watts instantaneously. In their dreams perhaps.

Ahhhh
Good old Harman marketing been doing this for years it resembles something that you would not want to step in while on a ranch

 

[annunaki]

I think that claim of 50A is meaningless. That amp will never put out at least 2500 watts instantaneously. In their dreams perhaps.

Remember efficency my friend. (I doubt it too.) Being a class A/B design, with 55% efficency as an average, it could peak at 1,375 watts or 196 watts peak per channel. That is not completely out of the ballpark. So in saying that it could be plausible.

 

[mtrycrafts]

Remember efficency my friend. (I doubt it too.) Being a class A/B design, with 55% efficency as an average, it could peak at 1,375 watts or 196 watts peak per channel. That is not completely out of the ballpark. So in saying that it could be plausible.

Ah, so they are talking 50A total, all channels combined? Or what are they really claiming??
But if they are claiming this at the speakers, all channels combined, the amp needs to supply 4545watts with your 55% efficiency. I think you went the wrong way?

 

[gene]

Being a class A/B design, with 55% efficency as an average, it could peak at 1,375 watts or 196 watts peak per channel. That is not completely out of the ballpark. So in saying that it could be plausible.

Actually real world class a/b amp efficiency is more like 35-40%. 55% is textbook nonsense, without factoring in power supply losses.

The 50A rating is instantaneous like others here have stated. Its impossible for their receiver to deliver anything more than 15A continuously based on the limits of the breaker, internal fuse, and UL approval.

 

[PENG]

The other formula - power = IxIxR. 50A squared is 2500 watts not counting R as 1. I seriously doubt it will ever be able to do this even instantaneously Let alone into a speaker load.

I'd like to see their dynamic capability first

mtrycrafts,

You are right, that's why I think the 50A they specified is not only an instantaneous value, it is the total currents. So if it is for 7 channels driven at the same time, then each channel only has to push 7.143A into each of the 7 speakers.

For 4 ohm loads, using you formula P=I square *R, that's approx. 7X7X4=196W per channel, or less than 1400W total. That's believable for a short burst of power/current, and as buckeyefan1 sort of said, it helps in explosion scenes as an example.

 

[mtrycrafts]

mtrycrafts,

You are right, that's why I think the 50A they specified is not only an instantaneous value, it is the total currents. So if it is for 7 channels driven at the same time, then each channel only has to push 7.143A into each of the 7 speakers.

For 4 ohm loads, using you formula P=I square *R, that's approx. 7X7X4=196W per channel, or less than 1400W total. That's believable for a short burst of power/current, and as buckeyefan1 sort of said, it helps in explosion scenes as an example.

OK, I guess I could see this is what they really mean without simply stating it. But then The amp efficiency also comes in to play as posted, about 55%. That would mean a 2500 watt spike on the mains?

 

[mtrycrafts]

Actually real world class a/b amp efficiency is more like 35-40%. 55% is textbook nonsense, without factoring in power supply losses.

The 50A rating is instantaneous like others here have stated. Its impossible for their receiver to deliver anything more than 15A continuously based on the limits of the breaker, internal fuse, and UL approval.

With the amp draw added up for the 7 outputs, about 1400 watts, with your 40%, that would need 3500 watts on the mains, 30A

 

[surveyor]

mtrycrafts,

You are right, that's why I think the 50A they specified is not only an instantaneous value, it is the total currents. So if it is for 7 channels driven at the same time, then each channel only has to push 7.143A into each of the 7 speakers.

For 4 ohm loads, using you formula P=I square *R, that's approx. 7X7X4=196W per channel, or less than 1400W total. That's believable for a short burst of power/current, and as buckeyefan1 sort of said, it helps in explosion scenes as an example.

Could it be that HK's marketing people are practicing the snake oil current theorms, or just plain full of hot gas?

 

[PENG]

OK, I guess I could see this is what they really mean without simply stating it. But then The amp efficiency also comes in to play as posted, about 55%. That would mean a 2500 watt spike on the mains?

That's about it (or as you know, higher, if the efficiency is lower), and assuming it must draw from the mains. Without backing up with any calculations, perhaps the capacitors are large enough to take care of that current spike. The spike would have to be really short. Again, I am not sure, hopefully other EEs on this forum who specialize in AV electronics could answer your question.

 

[shokhead]

On another forum,I'm told that HK is low budget,is that true?

 

[annunaki]

Actually real world class a/b amp efficiency is more like 35-40%. 55% is textbook nonsense, without factoring in power supply losses.

The 50A rating is instantaneous like others here have stated. Its impossible for their receiver to deliver anything more than 15A continuously based on the limits of the breaker, internal fuse, and UL approval.

Gene,

At full power, I have seen many class A/B amps near the 55% range. Doesn't efficency figure in power supply losses as part of the equation? I know thatthe efficency dips quite a bit at 1/3rd or 1/2 power to the 30% range (or lower depending upon bias), but I was not aware of that (power supply losses not figured into efficency at full power). I am not saying you are wrong, I just have not heard that mentioned.

I was more or less playing devil's advocate anyway.

With a 50A +/- (mtrycrafts 2500 watts) current capacity using a 40% efficency number that would be about 142.88 watts peak per channel (all 7). However, in doing my own calculations 50A at 110 volts is 5,500 watts (IxV=W). Most outlets (20 amp) would not like this too much. Though a transient short burst peak could potentially be that high without tripping the breaker (which is what we are talking here).

Using the 5,500 watt number, at 40% efficency it would be 314.29 peak watts per channel. This is where it is completely unbelievable, and I would say impossible. It would depend upon the voltage that the 50A was taken at. In any aspect, I would say do not look into it too much, as it looks like BS.

 

[gene]

At full power, I have seen many class A/B amps near the 55% range.

Again this is a text book # assuming perfect lab conditions with no power supply losses. The truth of the matter is transformers saturate, hysteresis becomes a factor. When you factor in all of the real world losses, 40% is actually still very generous and rarely achieved. We are constructing a series load to probe inputs of amplifiers to measure efficiency and will soon write articles on this topic. You will be surprised how very little power you are actually using in todays HT systems that all feature powered subwoofers and usually 90+dB efficient speaker systems.

As for the 50A rating, again thats an instantaneous rating, much like dynamic power than Denon/Yamaha state, though the latter are IEC rated. I am not sure if Harman conducts this test to any known standard but I will check on it.

Don't get too caught up in these ratings. Power is power anyway you look at it, and companies can only deliver so much at a certain price point based on the laws of physics and profitability.

Please read the following refresher article:

Product Managing Receiver Platforms & Power Ratings

 

[mtrycrafts]

On another forum,I'm told that HK is low budget,is that true?

No, it is not but it has limits. Whatever its rated RMS power is, that is what HK is.