High current amplifier

[pinion9]

I recently purchased a receiver from Hardon Kardon (avr240). It is a 7.1 and retails for $600 or so. It is 50 watts per channel, which seems low. However, several people chimed in and said that it is high current though and the website does claim +/- 35 amps.

So, please explain to me why 50 watts of high current would be better than 150 watts of low current.... or am I missing something?

 

[PottedMeat]

maybe more easily drive lower impedance speakers?

 

[bobsmith1492]

35 amps for what, the output current? That makes absolutely no sense... that would be driving a 0.0408 ohm speaker, which is basically a couple of feet of straight wire. Something is wierd about the numbers you're saying. I think people are making stuff up. Most speaker system power numbers are waaaay overrated, like a 1us peak power number at 25%THD or something rediculous like that.

 

[PottedMeat]

Hmm

Here is the Manual for the HK AVR240:

Harmon Kardon AVR240 - Tech Specs on Pg 57


It just says 'High Instantaneous Current Capability +/- 35 Amps'
65W/Channel Stereo Mode 0.07%THD into 8 Ohms

and 50W/Channel 0.07%THD into 5 Channels into 8 Ohms

Searching around, it looks like this is just a marketing term, can't really find an actual definition.

 

[dkozloski]

I suspect there is a semantics problem here. I think "High" refers to amount and not position. Using that premise then the marketing shpeil says you can get a pretty good spike for an instant. Forty years ago I had an H-K amp with the same kind of overhyped specs that went up in smoke before coming close to the claimed performance.

 

[pinion9]

I don't think so...many people have mentioned it to me. That is why it is a $600 receiver. This is what Crutchfield says:

High-current power
The flow of current through your speakers' voice coils creates the electromagnetic force that moves the cones and domes, creating sound. The dynamic qualities of music and movie soundtracks create short-term high-current demands. If current flow is limited, the sound will be, too. A high-current amplifier (or a receiver that uses one) may sound punchier and more powerful than other models with the same wattage rating.

Many, many of the reviews I have read state that it is louder than some of the 100 watt/channel amplifiers they have used, etc. etc. I was just wondering WHY it makes a difference? I pretty much though that watts are watts, e.g. 2a @ 120v = 1a @ 240v. Apparently untrue....

 

[pinion9]

Originally posted by: dkozloski
I suspect there is a semantics problem here. I think "High" refers to amount and not position. Using that premise then the marketing shpeil says you can get a pretty good spike for an instant. Forty years ago I had an H-K amp with the same kind of overhyped specs that went up in smoke before coming close to the claimed performance.

Hmmm..I think this makes sense, in conjunction with what Crutchfield says. Apparently that pretty good spike for an instant is what makes movie soundtracks come alive (hence the reviews saying it is more responsive and punchier.)

From what I understand, H-K is pretty good mid-level theater equipment now. I appreciate that they don't exaggerate their claims (they claim 50w/channel, whereas some other $150 pioneer receivers claim 150 watts) I don't think I did too bad considering it was $280 from Amazon, brand new.

 

[Tiamat]

Typically, high current means that the amplifier is more apt to double the power for half the impedence.

For instance, I would say that an amplifier that does:

50 Watts into 8ohm, 75 watts into 4 ohm = is NOT high current.

50 Watts into 8 ohm, 100 watts into 4 ohm, 200 Watts into 2 ohm, 400 Watts into 1ohm, 800 Watts into 0.5 ohm = Very high current amplifier.

High current amplifiers typically refer to their ability to allow high current to pass through the electronics without burning up. The case has enough heat dissipation to deal with the heat associated with high current. Additionally, the parts are quality enough to handle large current flow through them.

You have to remember that even 8 ohm speakers dip down into 4ohm and below for certain frequencies. The 8 ohm figure is typically only at 1000hz frequency. Some speakers, for instance, will dip to 3.5ohm at 50hz. Others will have high impedence at that frequency due to a tuning port being tuned to that frequency.

 

[dkozloski]

The H-K amplifier I had was advertised at 60 Watts per channel. I was using Wharfdale W90 speakers at 4 ohms. The amp had 4 amp fuses in the output. 4x4x4 =64watts. I threw it in the dump and bought a Marantz amp advertised at 150 watts per channel. Rather than being fused it had temperature controlled current limiting circuitry. With the same speakers and a sound demo tape I had the neighbors out in the street looking for low flying aircraft. My conclusion was that the H-K was a misrepresented POS.

 

[f95toli]

Tiamat is correct: "High-current" refers to the capability to "drive" the speaker regardless of the impedance. A "perfect" amplifiers should double the power as the impedance is divided in half.


Even cheap amplifers are often rated at e.g. 100W at 8 ohms but then the power might only be e.g. 150W at 4 ohms, meaning the amplifier is "struggling" when the impedance drops. Some really "nasty" speakers have impedances that go down to 1 ohm or so, meaning that if the amplifer is rated 100 W at 8 ohms it needs to be able to deliver 800W at 1 Ohm.Very few amplifiers can do that.
Hence it might be better to use use a 50W amplifier that is less "sensitive" to the load.

My power amp at home is rated 150W at 8 ohms but doubles almost all the way down to 2 Ohms (I think it is rated 580W at 2 ohms continous load or something like that) but I guess you could consider that to be a"high-end" amp.

Note however that a cheap $600 receiver is very likely to be limited by its power supply. Hence, it is very likely that it can only deliver 100W in ONE channel. not all 5, even for a very short time (my reciver is ratex 7x110W, it can't even get close to that in more than 2 channels at a time). There are really good power amplifiers that can handle 5 channels but then we are talking about very expensive "monsters" (e.g amplifiers from Bladelius, Classé or Krell, the latter brand makes amplifiers that can generate an enormous amount of current; they sometimes demonstrate that by using them to weld).

 

[adwilk]

Yeah, your 600 dollar amp is a good one... and the 50 watts is probably pretty steady, as opposed to the 100 watts found in the wal-mart special. Keep in mind that the "watts" has oh so little to do with volume compared to other specs of other components... ie, speaker sensitivity. You probably have entry level or mid level speakers so keeping a clean signal is gonna be more important to you anyways. The HK reciever will play plenty loud, you saying "twice as loud as other receivers" or something like that leads me to believe that this receiver will treat you just fine since you arent looking for the best in sonic quality. Most people forget to realize that in most cases, its the speakers you use that result in a lack of headroom... At least you didnt buy bose.