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Good question over on "Planar.."
Follow Ups:
Dear Sir,I would definitely recommend to try any amp with the speakers of your choice before buy.
A real speaker is usually very far from behaving like a pure resistive load and efficiency also play an important role.
Specifications do not tell enough IMHO of course.
For instance, I had the opportunity to test two amps on my Dynaudio speakers: one specified at 90W/4 ohm and the other specified at 130W/4 ohm.
The first was so much more powerful than the second, even if specified at less power on a 4 ohm load.Kind regards,
beppe
God damn salesman invented this term. Any engineer would rather kill himself than call an amp "high current". If he does, then he is a salesman (like 90% of people here), not engineer of any kind.
Well I'm an engineere, degree and everything, and I KNOW the term has meaning.
Come on man. Here is hoping you can come up with a valid reason to believe what you say.At least if you expect people to buy the appeal to authority argument you offer: "I am an engineere" you could supply credentials such that those that might question the validity of your argument could be satisfied by knowing that you are indeed working in a relevant sector of the industry or have attained degrees from a respected university etc. It has been important enough for you to contradict the posts of people who have even posted valid arguments. Why wouldn't it be important to you to give people a sense of why they might want to believe you. What you have said thus far just isn't satisfying.
What does "high current amplifier" mean, and what specs can be used to verify a manufacturers claims of a product falling under the category? After all you contradict me with such authority. One would assume that there must be a better argument than : Nuh UHHH cause I'm an engineer. Even my six year old could see through that one.
please define the term
I just can't spell engineer...everything else works!
> Any engineer would rather kill himself than call an amp "high current". <Perhaps even the engineer that wrote the above statement? Or just wishful thinking.......????
I say it is all a marketing ploy and adds nothing more to the ability to understand an amplifiers capabilities than the traditional specs already can tell you.As far as my admittedly limited experience in audio equipment leads me to believe, all of our audio amplifiers are technically voltage amplifiers. A voltage amp by definition will supply whatever current that is necessary to maintain a voltage across the load. The voltage it is giving to the load is simply the input voltage multiplied by the gain. Obviously there will be limits on this capability in the real world due to using imperfect components to build and power the voltage amp but these limits are the very issues that the higher quality amplifiers adress. Furthermore a reputable manufacturer will make these limitations obvious in the spec sheets. This has worked very well through history and oddly enough (not) the engineers could get designs built and stable without this useless high current amplifier labeling. I think my biggest problem/complaint with this label is: what is it's technical definition? From what I've seen it is just some meaningless label that is pulled out of, well....
Although I gotta admit it does sound cool. I am sure that is exactly why it is a "spec" now.
Here is an example: this term didn't show up until when???? the late eighties early nineties. I think the loudest concerts in history (if memory serves me) the "Who" shows back in the late seventies and early eighties were the loudest without the use of amplifiers containing this label. hhmmmm.
Please feel free to correct me where I am wrong and point out the errors in my post. I am not too proud.
The first time I heard the term "high current amp" was in 1978, and I was told by the manufacturer of electrostatic loudspeakers that I would need a "high current amp" to properly drive their panels.And I would imagine the term was around a lot longer than that!
"And I would imagine the term was around a lot longer than that!"I would imagine theat since it doesn't mean anything now it never did.
There is no FTC guidline for current as there are for power output (e.g. 100 watts per channel from 20Hz to 20,000Hz at 0.05% THD). Without standard measurement conditions, comparing the few amplifiers that actually have a number published is meaningless. That said, I generally regard an amplifier as "high current" if it is capable of driving low impedance loads effectively. A very good solid state amplifier will effectively double power output as the speaker impedance halves (e.g. 100 watts inot 8 ohms, 200 watts into 4 ohms, etc...). This usually requires an overspecified power supply and rugged output devices with no "current limiting" circuitry.
Dear rkeman,I've read your previous article regarding Wadia 25 posted on Aug. 22 2003.
I'm quite interesting to get one of the second hand Wadia 25 to direct link to my Krell KSA-300S power Amp. But unfortunatively, I can not find any manual from Wadia or from the web. I need to know how to set those setting inside Wadia 25 for the gains.
Since you already won one of this DAC. Would you please kindly let me have one of Wadia 25 manual or simply show me how to set these setting.
Your help would be much appreciated.
But the FTC rating does give you an idea about current. Power equals current squared multiplied by the resistance, in this case 8 ohms. I have never understood why audiophiles talk about power and current like they are unrelated. By nature they can't be.Of course I am talking about the actual power and current delivered by the amplifier. The published specification is something else again. My general take is that if the spec is not quoted in FTC terms, meaning with frequency bandwith and distortion percentages, take it with a grain of salt.
In general, I agree with your statement concerning driving low impedance loads. Another good specification to look at is called dynamic headroom, which is how much power an amplifier can deliver over a 20 millisecond burst. This is expressed in decibels in relation to the FTC constant power rating. So a 40W amplifier with 6DB of dynamic headroom can instaneously deliver 160W.
Audiophiles obsess over amplifiers constantly. You see people asking questions here every week about Class A vs class AB, tube vs transister, negative feedback, high current, and so on. Most of the people who ask these questions don't even really know what any of these things mean. The reality is that there are actually very few loudspeakers that need to be attached to an arc welder to operate.
It is not an audiophile thing it is an educated persons thing.It is most maddening to those who have studied electrical theory to hear about these terms which are neither necessary or mean anything.
It is a term invented by someone to make something sound cool not describe any aspect of it's performance.
Why, because there was already terms created for all of the terms which describe the performance and there needs to be some new mystical properties about some new device in order for it to sell well. If you can't actually be creative and come up with innovative new technologies then just hire a good marketer to come up with terms like "high current amp".
With the knowledge you gave above how do we figure that out from reading the product literature.Example: My new Usher CP-6371 states 4 ohm with 120watt max.
What SS or Tube amps would be best suitable statwise...2 Way --1" Tweeter -- 2 x 7" Mid-Bass
Sensitivity:90dB 1watt/1m
Nominal impedance: 4ohms
Frequency response (-3dB): 30Hz~28kHz
Power handling:120watts
Crossover frequencies: 2.7Hz
Weight : 115lbs Each
Dimensions(wxdxh):35cmx65cmx127cm
_______________________________________*Analog fans may be blind-but digital fans are deaf*
http://www.flickr.com/photos/82495693@N00/
How can you tell if it's a high-current amp?Are you sure you know what you mean by high current?
Why do you want a high current amp?
An SS amp will definitely be high current if it just about doubles it 8 Ohm power into a 4 Ohm load and does about the same into 2 Ohms. You can't do this without lots of amps.
I think:
High current amps are A) for playing insensitive speakers that have low impedence dips and B) heavily marketed as being "better than" amps that have a much flatter current response as loads change.
See Link below
- http://www.audioholics.com/techtips/audioprinciples/amplifiers/HighCurrentAmps.php (Open in New Window)
Read the specs.. :-) Some Amps DO list it Others that don't are simply not worth considering and do note that Price is NOT the determinant..competent design is.. you might be pleasantly surprised.
In fact it was my post - and your response here begs the question: what is the "spec" that we should look for? I just reviewed Quicksilver's website for specs on my amps (V4s) and found nothing but "Power output" (listing 120 wpc into 8 ohms), but a review of ARC's website listed "OUTPUT CURRENT: 25 amps peak at protective shutdown" for their 300.2 SS amp. Now if this is the spec for which we should look, can you advise on what the above spec means, and whether that is a good spec for planars?
Mark Levinson ML-2's advertised 25 amps of peak current even though the amp was rated at 25 watts. I believe Audio magazine actually took their advertising to task and did some welding with the amp or some other ML product. HK receivers (HK owns ML now, BTW) have high current capability. Their cheap 75 watt receivers boast of +/- 40 amp capability and it shows in their ability to control large woofers and to drive difficult impedances (I believe their internal speaker fuses were set to go at .8 ohm loads).
Most tube amps have limited current capability, the exception being the amps which run the 6C33 output tubes which have very high current capability. Each tube runs two filaments and two cathodes in order to give the high current current.
Quicksilver actually makes a triode amp using a pair of these tubes and it sounds more controlled and powerful than the higher wattage v-4's. It certainly controls certain power hungry speakers better than any other tube amp I have tried despite its relatively lower power.
Dear Sir,I wonder if the HK claim of +/- 40 amp capability is realistic.
40 A peak should mean 6400 W peak on a 4 ohm load !
Am I missing anything ?
The figure seems not reasonable to me.Kind regards,
One of the reasons why a max current spec is meaningless is because the load impedance and other test conditions are not given. Most likely the load impedance at which they achieved 40A is 0.1 ohms or less. It's just a test to see how close they can get to a short circuit before the protection circuit kicks in or they blow a fuse or a transistor. When hooked up to a 4 ohm loudspeaker load, the amp will never put out anything remotely close to 40A. The output voltage will hit the rails and clip long before then.
Well that is not exactly true since as I pointed out it would be possible to use step up transformers in the power supplies. Another way to get there would be to use some type of switching power supply. Even then however there is no way to maintain that type of power output for any significant length of time, well no reasonable way that is. The point is: it would be possible to build an amp which could temporarily supply 40 A to 4 ohms off standard 120VAC 60Hz, but it would definitely be one capacitor laden beast in order to be useful like that for music even if that was the absolute peak output.
Sure, with a large enough bank of capacitors and a high enough power supply voltage, one theoretically _could_ build an audio amplifier that delivered 40A and 6.4kW(!) peak into a 4 ohm load. But these "high current" designs have typical rail voltages and typical power supply capacities. I wouldn't go so far as to say this is universally true, but the one thing that seems to differentiate most so called "high current" designs from the norm is the use of many output devices in parallel. Because of that, I think the high current fad is much like the high damping factor fad that preceded it - they are both synonymous with low output impedance.
Dear Sir,if you had to predict the "ability" of an amp to drive properly a difficult load (low impedance, low sensitivity, etc.) which figures in the specifications would you consider?
This is a fundamental problem for me because I always bought without trying before, with bad luck.Thank you very much indeed.
Kind regards,
Unfortunately, I find the common set of specifications to be inadequate for predicting how well an amplifier mates with specific speakers. So there's no substitute for an audition. I mostly look at specifications to ensure general compatibility. I usually try to select a "short list" of components to audition based on specifications, design information, reviews, and word of mouth.The specification I start with is power output into the speakers' nominal impedance, ie. continuous rated power into 4 ohms for 4 ohm speakers. The amount of power you need will depend on how loud you listen, the sensitivity of your speakers, the size of your room, the distance from the speaker to the listener, and other minor factors. So the number varies situationally. If you know all the variables, you can do a rough calculation to estimate how many watts you may need to reach the desired peak SPL.
Assuming we are talking about solid state amplifiers, the next thing I look at is the dynamic headroom specification, if available. The dynamic headroom spec tells you how much peak power is available for transients, above and beyond the continuous rated power spec. For example, if the continuous rated power is 100W and dynamic headroom is 3 dB, then up to 200W is available in short burts. I try to consider dynamic headroom when trying to determine whether an amplifier has enough power to drive my speakers.
If a dynamic headroom spec is not available, I look at the power supply transformer rating and capacitance. An amplifier with a generously oversized power supply is often able to deliver significantly more than its continuous rated power for short transient bursts. So an amplifier rated for 100W into 8 ohms with a 500VA/50mF power supply will usually have greater dynamic headroom than another 100W amp with a 250VA/30mF power supply.
If your speakers have a "roller coaster" impedance curve, or really low impedance dips, or a combination of low impedance and large phase angle, then it is also important to look at output impedance or damping factor (they are inversely related). Again I assume we are talking about solid state amplifiers. The lower the output impedance or higher the damping factor, the less affect the impedance will have on the speaker's frequency response.
I would also look at input impedance, input sensitivity, and gain just to ensure compatibility with your pre-amp.
Some specifications that I do not look at are frequency response, THD, SNR, slew rate, and maximum current. All solid state amplifiers have essentially perfect frequency response, THD, and SNR specs so I don't think they are useful in differentiating performance. Slew rate is basically just another way of stating frequency response, albeit in a power dependent way. And as we already discussed, maximum current is usually measured into unrealistic and unspecified loads, and I can usually figure out how well it will drive difficult loads from the power and damping factor/output impedance specifications.
Unless your speakers are a really tough load, I think you'll find there are a lot of amplifiers to choose from if the only criteria are compatible specifications. In order to narrow down the list, I would try to talk to other people using the same speakers and find out what they are using, or what the manufacturer recommends, or what is used to demo the speakers at shows or at dealers. And if you listen to a lot of different equipment, you will probably learn what kind of designs are most likely to please you.
Dear Mr. Kingsland,I thank you very much for your extremely kind and valuable reply.
You have helped me a lot to understand much better the all issue.
I will try to listen before buy, as you recommend.
Thank you again.Kind regards from Italy !
Thank you very much for the kind and valuable explanation.
Actually I was missing that a figure of Apeak without any indication of the corresponding load is just incomplete.Thank you and kind regards,
Dear Mr.Kingsland,thank you very much for your kind and extremely helpful reply.
I understand that a figure without any reference to the actual test conditions is not very useful.Thanks and regards,
HK is claiming the ability to put 40A through 4ohms? I think the only way that is possible, at least in standard US living rooms, is if they use a step up transformer in the power supply. Even then, unless there is something special about the mains circuitry it will only be an instantaneous value as there is no way a standard 115VAC 20A mains circuit is going to support that type of load. Now maybe if you are in the UK and using a 20 amp circuit you might get close to keeping up.
Dear Sir,you mention that at ARC they state an OUTPUT CURRENT of 25 amps peak at protective shutdown for their 300.2 SS amp.
Would that be 2500 W peak on a 4 ohm load ?
Or am I missing something ?
Wow ! that is a lot indeed.Thank you very much.
Kind regards,
Can't tell you because doesn't say. And ARC doesn't appear to reveal this spec for all of its amp products either.
As you can read above I was misunderstanding the peak current figure.
Without the indication of the testing load (ohm) it is just incomplete.Kind regards,
It is high current if it can close to double its power output into 4 ohms and so on. There are many high current amps running around out there that do not make a big deal out of this. Maybe because there are some drawbacks they don't want to tell you about....???
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