High Instantaneous Current Amp Spec

[mtrycrafts]

An interesting footnote on the HKAVR330:

When driving multichannel 4-ohm loads with steadystate
test signals (sine tones), the receiver activated
its protection modes after about half a
second if it was asked to produce more than
about 25 watts. Single-channel performance
was unaffected, and real-world dynamic signals
presented no problem with these low-impedance
loads..

Not a very high current amp, is it?

 

[PENG]

Not a very high current amp, is it?

I guess not, but again, HK only specifies high instantaneous current, read their instruction manual. Sorry about quoting this "instantaneous" thing the umpteenth time.

 

[mtrycrafts]

I guess not, but again, HK only specifies high instantaneous current, read their instruction manual. Sorry about quoting this "instantaneous" thing the umpteenth time.

Yes, but what does that really mean? Can it do those claimed current outputs to be a real effective dynamic headroom, 20 ms or so, or is their instantaneous rating in the microseconds that is useless for anything.

 

[mike c]

then urban legend it is! thanks a lot guys! (i really appreciate this, one less thing bothering me)
thats all this dummy needs to hear.

 

[PENG]

Yes, but what does that really mean? Can it do those claimed current outputs to be a real effective dynamic headroom, 20 ms or so, or is their instantaneous rating in the microseconds that is useless for anything.

We would have to ask HK. My bet is that it will do more than a few microseconds. Its high instantaneous current capability should allow it to hit hard on demand, even if the load impedance drops down to below 4 ohms.

On the other hand, the RX-V1500 probably has higher current capability, it claims 330W, 1 channel "dynamic" power into 2 ohms (microseconds?, or milliseconds?).

 

[jaxvon]

It would have to milliseconds, as microseconds would be a useless quantity in audio. Besides, "miliseconds" is abbreviated "ms" and microsecond is abbreviated as [mu]s.

 

[PENG]

Mike C, don't get me wrong, high current capability is a good thing. What is urban legend is the claim that 55 HK watts=100 Yamaha watts due to HK's high current thingy.

In reality, ohms law and other basic electrical principles still rule. You cannot have high current unless the load demands it. The load will only demand "high" current if
1) the source material demands it.
2) the impedance of the load (speakers) drop way below the nominal 8 ohms, e.g. less than 4 ohms
3) the volume is crank right up.

1)&2) don't happen at the same time very often and when it does it won't last very long.

Besides, if an amp can deliver high currents, it should, in general, deliver high power as well. Power(Watts)=Current(Amperes)X CurrentXResistanceX Power Factor so power is proportional to the square of current. So it is pretty hard to get low power, yet high current.

 

[PENG]

It would have to milliseconds, as microseconds would be a useless quantity in audio. Besides, "miliseconds" is abbreviated "ms" and microsecond is abbreviated as [mu]s.

I agree, at least ms, if not 1 sec.

 

[macersl]

Statement 2 first;
Yes, the Yamaha 120w claim is BS. But no more so than most of the Japanese reciever's claims to power. That spec is not "all channels driven".

Absolute bs. Did Yam claim this power with all channels driven??? Or is it your desire for them to rate their amps as such???

HK is definety more true with their power claims than Yamaha, Denon or Sony.

Nonsense. They just make a different claim, period.

I see what your saying, but don't you think they kind of imply it when they post 120w X 7? And then also post the total watts?

 

[Votrax]

Mike C, don't get me wrong, high current capability is a good thing. What is urban legend is the claim that 55 HK watts=100 Yamaha watts due to HK's high current thingy.

In reality, ohms law and other basic electrical principles still rule. You cannot have high current unless the load demands it. The load will only demand "high" current if
1) the source material demands it.
2) the impedance of the load (speakers) drop way below the nominal 8 ohms, e.g. less than 4 ohms
3) the volume is crank right up.

1)&2) don't happen at the same time very often and when it does it won't last very long.

Besides, if an amp can deliver high currents, it should, in general, deliver high power as well. Power(Watts)=Current(Amperes)X CurrentXResistanceX Power Factor so power is proportional to the square of current. So it is pretty hard to get low power, yet high current.

Well said. I believe HK’s “High Instantaneous Current Capability” refers to their power transformer/capacitive filter output and not for a single speaker output. If it were for one channel it would require a speaker impedance of less than one ohm to draw that much current. Of course the output transistors are nowhere rated that high. On a side note HK receivers are not slouches and generally deliver what they are rated at.

 

[MDS]

.....I got one question concerning this all-channels-driven rating....using the 5 or 7 channel stereo mode, 5 or 7 channels aren't peaking at the same time?.....

All channel stereo is really a DSP mode. The processor takes the two stereo channels and sends them to the front speakers, just as in normal stereo mode. It duplicates those channels and sends them to the surrounds. It also sums the two channels and sends that to the center. So IF the two front channels peak at the same time, then the other channels would seem to peak at the same time too.

But that is a very rare case because:
1. Music rarely, if ever, is identical in each channel. I've edited enough audio with Sound Forge to state that pretty confidently. Of course there are some peaks that are nearly identical but not quite. I have yet to see any waveform where if you invert one channel and paste-mix it into the other, the result is all zero samples (ie, identical content).
2. In a typical HT setup, you are not equidistant from each speaker and the processor will apply a delay to some of the channels according to the speaker distance you set during setup.
3. The processing itself takes time, albeit an inaudible amount of time, so each channel will not require power at the exact same instant of time.

 

[mike c]

That's one of the many urban legends...'55 HK watts is like 100 Yamaha/Denon/Onkyo watts'.

thats the exact line they used on me. i didnt know they made the same claim there.

 

[mtrycrafts]

I see what your saying, but don't you think they kind of imply it when they post 120w X 7? And then also post the total watts?

Nope, not at all. But, I can understand how some would read between the lines. Unfortunate.

 

[mtrycrafts]

thats all this dummy needs to hear.

Hardly. You ask questions to learn and expand your knowledge. Don't put yourself down.

 

[mtrycrafts]

We would have to ask HK. My bet is that it will do more than a few microseconds. Its high instantaneous current capability should allow it to hit hard on demand, even if the load impedance drops down to below 4 ohms.

On the other hand, the RX-V1500 probably has higher current capability, it claims 330W, 1 channel "dynamic" power into 2 ohms (microseconds?, or milliseconds?).

Well, if Yam stated dynamic power, then it must follow the FTC rules on measuring dynamic power, 20 milliseconds, twice a second.

Now, if HK would only print their dynamic power, we could compare it properly

 

[mtrycrafts]

. On a side note HK receivers are not slouches and generally deliver what they are rated at.

Yep, they deliver what they print Some want to make more out of it though

 

[PENG]

One good thing about this thread is that people can debate the two somewhat related topics (high current/all channel driven) fully and freely without getting the original poster upset. I hope Gene won't really give up on us here.

 

[Dan Banquer]

High Amperage

I posted this on the all channels driven thread and then noticed this thread so I am going to post this here also. Hope it helps.

Let's take a look at what 75 amps peak current means mathematically when it comes to power: The following numbers are derived from the good old formula for power which is the square of the current times the resistance.
For 8 ohms that equals 45,000 peak watts. If we divide by 5 we get 9,000 peak watts per channel.
For 4 ohms that equals 22,500 peak watts. If we divide by 5 we get 4,500 peak watts per channel.
For 2 ohms that equals 11,250 peak watts. If we divide by 5 we get 2,250 peak watts per channel.
After looking at those numbers does anyone think their unit has the headroom in voltage to actually do that?
Does anyone here possibly think that the voice coils of their speakers can actually handle that?
After looking at these numbers does anyone here think that this is at all applicable to home theater especially when the impedance of Home Theater speakers drop only to 4 ohms?
After looking at these numbers does anyone still think that instantaneous peak current spec is at all relevant?
d.b.

 

[MacManNM]

I posted this on the all channels driven thread and then noticed this thread so I am going to post this here also. Hope it helps.

Let's take a look at what 75 amps peak current means mathematically when it comes to power: The following numbers are derived from the good old formula for power which is the square of the current times the resistance.
For 8 ohms that equals 45,000 peak watts. If we divide by 5 we get 9,000 peak watts per channel.
For 4 ohms that equals 22,500 peak watts. If we divide by 5 we get 4,500 peak watts per channel.
For 2 ohms that equals 11,250 peak watts. If we divide by 5 we get 2,250 peak watts per channel.
After looking at those numbers does anyone think their unit has the headroom in voltage to actually do that?
Does anyone here possibly think that the voice coils of their speakers can actually handle that?
After looking at these numbers does anyone here think that this is at all applicable to home theater especially when the impedance of Home Theater speakers drop only to 4 ohms?
After looking at these numbers does anyone still think that instantaneous peak current spec is at all relevant?
d.b.

You want to bet? This is a test of an electrovoice 15" driver I performed a few years ago. This woofer took 22.66 kW for more than 1ms. We tried to increase it but it blew up.

 

[Dan Banquer]

Receiver Power?

Want to try that on a typical driver used in a Home Theater Speaker? Not a 15" Subwoofer that was designed for sound reinforcement.
d.b.